Module No E03 Electrical Test Equipment Basic

PET RO N A S

GA S

TRAINING MODULE

ELECTRICAL (BASIC)

TITLE : MODULE NO :

TEST INSTRUMENTS E03

Capability Improvement Dept.2004 For Internal Use Only

DUTY NO 15: TEST INSTRUMENTS OBJECTIVES Upon completion of this module, the technician would be able to demonstrate knowledge and understanding on the following: 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15.

Safety precautions in test & measurement Basic construction and operation of Multimeter (Digital & Analog) Functional selection, setting of Digital Multimeter Use of digital multimeter and test procedures. Theory of Insulation measurement Basic construction and operation of Insulation resistance tester Functional selection, setting of Insulation resistance tester Use of digital Insulation resistance tester and test procedures. Basic construction and operation of Clamp on Ammeter Functional selection, setting & use of Clamp on Ammeter Theory of Earth Resistance measurement Function and operation of Earth Resistance tester Preparation and set-up of Earth Resistance tester Function and operation of Loop tester and RCD tester Preparation and set-up of Loop tester and RCD tester

16. test procedure & circuitry

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TABLE OF CONTENT 1.0.0 Introduction.............................................................................. 5 2.0.0 Safety........................................................................................ 6 2.1.0 Causes of Electrocution..........................................................................8 2.2.0 Use of High voltage protection equipment ...........................................8 2.2.1 Clearances ..................................................................................................................9

2.3.0 Section 2 Safety of BS 6626: 1985 .......................................................10 2.3.1. Responsibility ..........................................................................................................10 2.3.2 Rules or procedure for safe systems at work ........................................................10 2.3.3 Isolation and access for maintenance ....................................................................11 2.3.4 Preparing for maintenance work .............................................................................12 2.3.5 Fire extinguishing equipment..................................................................................13 2.3.6 Testing.......................................................................................................................14 2.3.7 Disposal of scrap......................................................................................................14

3.0.0 Multimeter .............................................................................. 15 3.1.0 Analog Multimeter..................................................................................16 3.2.0 Digital Multimeter ...................................................................................17 3.2.1 Voltage Measurements.............................................................................................20 3.2.2 Current Measurements.............................................................................................21 3.2.3 Resistance Measurements.......................................................................................21

3.3.0 Digital vs. Analog Multimeters..............................................................22 3.4.0 Safety Precautions.................................................................................22

4.0.0 Insulation resistance tester (Megohmmeter) ...................... 23 4.1.0 Analog Megohmmeter ...........................................................................23 4.2.0 Digital Megohmmeter ............................................................................24 4.3.0 Insulation resistance test......................................................................26 4.3.1 Components of DC leakage current ........................................................................26 4.3.2 Determining The Polarization Index ........................................................................27 4.3.3 Correction for Winding Temperature ......................................................................28 4.3.4 Insulation Contamination.........................................................................................29

4.4.0 Insulation resistance test methods......................................................29 4.4.1 Spot testing...............................................................................................................29 4.4.2 Step voltage test .......................................................................................................30 4.4.3 Time resistance test .................................................................................................30

4.5.0 Safety Precautions.................................................................................30 4.6.0 Insulation resistance (IR) test on Cables ............................................31 4.7.0 Insulation resistance (IR) test on Transformer...................................32 Electrical test instruments Module 03 (Basic)

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4.8.0 Insulation resistance (IR) test on Motor/Generator............................32

5.0.0 Clamp on meter ..................................................................... 34 5.1.0 Theory of operation of AC Clamp on meter ........................................35 5.2.0 Theory of operation of AC/DC Clamp on meter..................................36 5.3.0 Specifications of Digital Clamp on meters..........................................37 5.4.0 Advantages of Digital Clamp on meter................................................37 5.5.0 Advantages of Digital over Conventional Type ..................................37 5.6.0 Applications of Digital Clamp on meters.............................................38 5.7.0 Clamp on meter operations (Fluke model 321/322)............................38 5.8.0 Safety Precautions.................................................................................40

6.0.0 Earth tester, Loop tester & Residual Current Device (RCD) tester................................................................................................ 42 6.1.0 Earth resistance .....................................................................................43 6.2.0 Principle of Earth resistance testing ...................................................44 6.3.0 Earth resistance test methods .............................................................46 6.4.0 Earth Loop resistance ...........................................................................47 6.5.0 Earth Loop resistance test....................................................................48 6.6.0 Digital Earth Loop resistance tester from Megger (L T5 and L T6) ..48 6.7.0 Applications & Use of Earth Loop resistance tester..........................49 6.8.0 Residual Current devices (RCDs) ........................................................50 6.8.0 Residual Current devices (RCDs) ........................................................51 6.9.0 Testing of RCDs .....................................................................................51 6.10.0 Digital RCD tester from Megger (CBT3 and CBT4)...........................52 6.11.0 Safety Precautions...............................................................................54

7.0.0 Attachments........................................................................... 55 7.1.1 Fluke multimeter manual.......................................................................55 7.12 Megger Manual BM80 .............................................................................55 7.13 Fluke Clamp on meter Instruction sheet ..............................................55 7.14 Megger Digital Earth Tester ...................................................................55 7.15 Megger Digital Loop Tester....................................................................55 7.16 Megger RCD Tester.................................................................................55

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1.0.0 Introduction Testing is performed to verify the integrity of electrical systems. Most of these tests are non-destructive in nature and can be used to provide a complete look at the status and age of the equipment. In this module, we will concentrate on the following electrical tests instruments: Multimeter (Digital & Analog) Insulation resistance tester Clap on Ammeter Earth resistance tester Earth loop impedance & RCD tester In this module included the some specific OEM instruction manuals for the above mentioned test set. The module basically prepared to train the technicians to read and interpret the OEM manuals of the test instrument, which is the required to perform the some of the tasks prescribed in POSS under duty no. 15. In the process, it covers the basic underpinning knowledge required to perform the required tasks. For gaining the expertise in the activities, detail study of the “Operation & Maintenance” manual of respective test instrument and hands on experience is necessary. Note: Testing of electrical distribution equipment requires experience and an understanding of the hazards involved. The test equipment used at your workplace may be different or from different manufacturer than the one discussed in the module. You are therefore advised to read and understand the manufacturer's specifications/ guidelines and make yourself well conversant before attempting any testing work or operating the test equipment.

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2.0.0 Safety In the interest of safety, all test equipment should be inspected and tested before being taken to the job site. There is no need to get to the job and find that the test equipment does not work. A thorough visual inspection (i.e., checking for broken meters or knobs, damaged plugs, or frayed cords) is important. Always perform an operational check. For example: On an ohmmeter, short the probes and ensure that you can zero the meter. A voltmeter can be checked against an AC wall receptacle or a battery. If a meter has a calibration sticker, check to see if it has been recently calibrated. For precise measurements, a recently calibrated meter is a more reliable instrument. Every person who works with electrical equipment should be constantly alert to the hazards to which personnel may be exposed, and should also be capable of rendering first aid. The hazards are electric shock, burns, and related hazards. Safety must be the primary responsibility of all personnel. The installation, maintenance, and operation of electrical equipment enforce a strict safety code. Carelessness on the part of the technician or operator can result in serious injury or death due to electrical shock, falls, burns, flying objects, etc. When an accident has occurred, investigation almost invariably shows that it could have been prevented by the exercise of simple safety precautions and procedures. Each person concerned with electrical equipment is responsible for reading and. becoming thoroughly familiar with the safety practices and procedures contained in all safety codes and equipment technical manuals before performing work on electrical equipment. It is your personal responsibility to identify and eliminate unsafe conditions and unsafe acts which can cause accidents. You must bear in mind that de-energizing main supply circuits by opening supply switches will not necessarily de-energize circuits in a given piece of equipment. A source of danger that has often been neglected or ignored, sometimes with tragic results, is the input to electrical equipment from other sources, such as back-feeds. Moreover, the rescue of a victim shocked by the power input from a back-feed is often hampered because of the time required to determine the source of power and isolate it. Therefore, turn off all power inputs before working on equipment, tag and lock out, then check with an operating tester to be sure that the equipment is safe to work on. Take the time to be safe when working on electrical circuits and equipment. Carefully study the schematics and wiring diagrams of the entire system, noting what circuits must be de-energized in addition to the main power supply. Remember, electrical Electrical test instruments Module 03 (Basic)

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equipment commonly has more than one source of power. Be certain that all power sources are de-energized before servicing the equipment. Do not service any equipment with the power on unless absolutely necessary. Remember that the 115V power supply voltage is not a low, relatively harmless voltage but is the voltage that has caused more deaths than any other medium. Safety can never be stressed enough. There are times when your life literally depends on it. The following is a listing of common safety precautions that must be observed at all times: Use only one hand when turning power switches on or off. Keep the doors to switch and fuse boxes closed except when working inside or replacing fuses. Use a fuse puller to remove cartridge fuses after first making certain that the circuit is dead. Ensure that you are qualified and authorised to work on an electrical circuit (LV or HV). Do not work with energized equipment by yourself; have another person (safety observer) that is qualified in first aid for electrical shock present at all times. The person stationed nearby should also know which circuits and switches control the equipment, and should be given instructions to pull the switch immediately if anything unforeseen happens. Always be aware of the nearness of high-voltage lines or circuits. Use rubber gloves where applicable and stand on approved rubber matting. Not all rubber mats are good insulators. Comply to PTW and inform those in charge of operations as to the circuit on which work is being performed. Keep clothing, hands, and feet dry. When it is necessary to work in wet or damp locations, use a dry platform and place a rubber mat or other nonconductive material on top of the wood. Use insulated tools and insulated flashlights of the moulded type when required to work on exposed parts. Do not work on energized circuits unless absolutely necessary. All power supply switches or cut-out switches from which power could possibly be fed must be secured in the OPEN (safety) position and perform LOTO. Never short out, tamper with, or block open an interlock switch. Keep clear of exposed equipment; when it is absolutely necessary to work on it, use only one hand as much as possible. Avoid reaching into enclosures except when absolutely necessary. When reaching into an enclosure, use rubber blankets to prevent accidental contact with the enclosure. Electrical test instruments Module 03 (Basic)

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Do not use bare hands to remove hot vacuum tubes from their sockets. Wear protective gloves or use a tube puller. Use a shorting stick (discharge rod) to discharge all high-voltage capacitors. Make certain that the equipment is properly grounded. Ground all isolated and discharged circuits of the equipment under test to prevent accidental charging. Turn off the power before connecting alligator clips to any circuit. When measuring circuits over 440V, do not hold the insulated test probes with bare hands.

2.1.0 Causes of Electrocution Unsafe Acts: a Accidentally slipping with wrenches, screwdrivers, etc., while working on or near electrical equipment with live parts (over 50 volts) a Switching off the wrong circuit and then failing to verify that the circuit is deenergized before beginning work. a

Failing to implement lock-out/tag-out procedures or use adequate protective equipment.

a

Use of noninsulated tools.

a

Wearing metal jewelry while working on live circuits.

a

Using instruments/meters/tools not designed for the system voltage.

a

Non-electrical personnel working too close to live equipment (e.g. power lines), usually with cranes or lifting equipment or handling metallic material.

Unsafe conditions: a

Improper grounding, loose connections, defective parts, ground faults, unguarded live parts or faulty insulation in equipment.

a

Inadequate maintenance.

a

Hazardous environments, e.g. corrosive or flammable atmosphere, wet or damp locations.

a

Inadequate working clearance.

2.2.0 Use of High voltage protection equipment Anyone working on or near energized circuitry must use special equipment to provide protection from electrical shock. Protective equipment includes gloves, leather sleeves, rubber blankets, and rubber mats. It should be noted that this electrical protective equipment is in addition to the regular protective equipment normally required for maintenance work. Regular protective equipment typically includes hard hats which are Electrical test instruments Module 03 (Basic)

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rated for electrical resistance, eye protection, safety shoes, and long sleeves. Gloves that are approved for protection from electrical shock are made of rubber. A separate leather cover protects the rubber from punctures or other damage. Gloves are rated as providing protection from certain amounts of voltage. Whenever an individual is going to be working around exposed conductors, the gloves chosen should be rated for at least as much voltage as the conductors are carrying. Rubber sleeves are used with gloves to provide additional protection. The combination of sleeves and gloves protects the hands and arms from electrical shock. Rubber blankets and floor mats have many uses. Blankets are used to cover energized conductors while work is going on around them. They might be used to cover the energized main busses in a breaker panel before you begin working on a deenergized breaker. Rubber floor mats are used to insulate workers from the ground. If a worker is standing on a rubber mat and contacts an energized conductor, the current cannot flow through the body to the ground, so the worker will not get shocked. 2.2.1 Clearances

Adequate clearances are to be maintained between energized and exposed conductors and personnel. Where DC voltages are involved, clearances specified shall be used with specified voltages considered as DC line-to-ground values. If adequate clearances cannot be maintained from exposed live parts of apparatus in the normal course of free movement within the area during test, then access to that area shall be restricted by fences and barricades. Signs clearly indicating the hazard shall be posted in conspicuous locations. This requirement applies to equipment in service as well as to equipment to which test voltages are applied. Whenever there is any question of the adequacy of clearance between the specific area in which work is to be done and exposed live parts of adjacent equipment, a field inspection shall be made by management representatives of the group involved before starting the job. The result of this inspection should be to outline the protection necessary to complete the work safely, including watchers where needed. An important piece of information is the minimum distance allowed when working near energized electrical circuits, because large voltages can arc across an air gap. Personnel must maintain a distance that is greater than that arc distance. This is especially true when using a hot stick to open a disconnect.

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These distances are listed in Table 1.

Voltage Range

Minimum Working and

(Phase-to-Phase) Kilovolts

Clear Hot Stick Distance

2.1 to 15

2 ft. 0 in.

15.2 to 35

2 ft. 4 in.

35.1 to 46

2 ft. 6 in.

46.1 to 72.5

3 ft. 0 in.

72.6 to 121

3 ft 4 in.

138 to 145

3 ft. 6 in.

161 to 169

3 ft. 8 in.

230 to 242

5 ft. 0 in.

345 to 362

*7 ft. 0 in.

500 to 552

*11 ft. 0 in.

700 to 765

*15 ft. 0 in.

* For voltages above 345 kV, the minimum working and clear hot stick distances

may be reduced provided that such distances are not less than the shortest distance between the energized part and a grounded surface. Table 1. OSHA Working And Hot Stick Distances At Various Voltages

2.3.0 Section 2 Safety of BS 6626: 1985 2.3.1. Responsibility

Electrical equipment should be regarded as being capable of giving rise to danger, not necessarily of an electrical nature, and it is essential that all persons responsible for electrical work make themselves acquainted with the relevant statutory requirements. A list of some relevant publications is included in the foreword, All persons concerned with the maintenance of equipment should conduct themselves in accordance with the provisions of the statutory requirements and take reasonable care for the health and safety of all those carrying out the work, and others who may be affected by their acts or omissions at work. A notice giving instructions for the treatment of persons suffering from electric shock should be affixed in a prominent position in the vicinity in which work on electrica1 installations will be carried out. It is strongly recommended that all electrical maintenance personnel be trained in the application of resuscitation and know how to summon medical help. 2.3.2 Rules or procedure for safe systems at work

It is recommended that in all premises, the employer or occupier should formulate and update, as needed during the life of the equipment, a set of safety rules or procedures, Electrical test instruments Module 03 (Basic)

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appropriate .to the type of electrical installation, covering the safe access for the purpose of maintenance to, and the operation of, the equipment on his premises. (See typical example in appendix D.) Where the employer or occupier is not competent to do this, the formulation of a set of safety rules may be contracted out to a competent authority. Where switching or maintenance work has to be done on equipment fed directly from a source of supply not under the control of the employer or occupier or the persons actually carrying out the work then special care is required. It will. Be necessary for all parties to mutually agree procedures and methods of work in order to ensure the safety of persons carrying out the work, and for these. agreed procedures to be incorporated in the rules and procedures for the installation. Care should also be taken to prevent equipment being worked on becoming energized due to the automatic or inadvertent starting of standby or emergency generators. In addition, the employer or occupier should ensure that precise instructions exist, based on the manufacturer's handbook for the safe handling, maintenance and testing of the equipment. The employer or occupier should also make .arrangements for monitoring to ensure that the foregoing procedures are effectively performed. Those concerned with the maintenance of equipment should familiarize themselves with the plant it controls and report any changes which may affect the equipment. During maintenance work all personnel should pay particular attention to warning notices or instructions incorporated on the equipment or set up temporarily during the maintenance procedures. 2.3.3 Isolation and access for maintenance

2.3.3.1 General The policy to be followed in making equipment available for maintenance should always be that it should be isolated and proved dead where possible and immediately earthed. 2.3.3.2 Procedures No electrical conductor should be regarded as being safe unless it has been isolated and discharged to earth and, where necessary earthed at all points of supply. Precautions should be taken to ensure that the isolated equipment cannot be reenergized from a high voltage or a lower voltage source of supply. Voltage indicators should always be proved before and after use. It is good practice to inspect earthing devices before every use. Earthing connections including leads and associated terminations need to be of adequate capacity for the duty at the point of application.

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Barriers preventing access to enclosures containing live conductors should normally be kept locked. Where one person isolates and another does the work, the person responsible for isolating should demonstrate effectively to the other that the equipment is in fact dead and safe and that there are adequate safeguards to prevent re energization. Adequate quantities of suitable locks, cautionary notices and temporary barriers should be available for use to facilitate safe working and to prevent conductors from being accidentally electrically charged when persons are working thereon and also to warn of the presence of any live conductors. Such notices should be clearly legible and prominently displayed, made from durable; material and kept up-to date. Suitable precautions should be taken to identify circuits and equipment at the front and back of switchboards where such identification does not already exist. . Any disconnectors used for isolation should be locked to prevent movement to the ‘ON’ position. Any shutters giving access to live conductors should also be padlocked in the closed position. Equipment enclosures frequently contain, circuits having sources of supply different from that of the main circuit, such as interlocks, alarms, heating and lighting circuits, etc., and these circuits are not always isolated when the main circuit is disconnected. Conductors and terminals associated with these circuits should be shrouded where necessary to prevent accidental contact and identified with warning notices. Particular care should be taken to avoid danger from reverse energization of voltage/control transformers or the open circuiting of current transformer secondaries. Removal and retention of fuse links or bolted links should only be used as a means of isolation when suitable precautions are taken to prevent duplicates being inserted. Contactors should never be considered as a means of isolation. Reliance should never be placed on control circuit isolation, switching or electrical interlocks to prevent accidental or inadvertent re-energization of the main or auxiliary circuits. Where the component to be maintained is completely withdrawn from the equipment, and thus from all sources of electrical supply, that component may be regarded as a safe piece of equipment and no longer subject to the safety rules referred to in paragraph 1 of clause 4. 2.3.4 Preparing for maintenance work

Working space, entry ways and exit ways provided to apparatus and to equipment which is to be maintained should be kept clean and free from obstruction. Spare parts, tools, instruments insulating screens, insulated tools, portable earthing devices and gloves Electrical test instruments Module 03 (Basic)

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associated with the equipment or the work to be performed should be housed in proper receptacles provided for the purpose, and kept in proper condition. Adequate lighting either fixed portable, or a combination of both should be provided as necessary to ensure safe access and working. Portable electrical tools and inspection lamps should preferably be operated from a system with a voltage no greater than 110 V with either the star point of a three phase or the mid-point of a single-phase transformer low voltage winding earthed. If mains voltage portable tools need to be used, they should be of all-insulated or double insulated construction and the use of a residual current device is recommended. All portable electrical equipment should be regularly inspected and tested. NOTE. Further advice on the safe use of portable tools is contained in HMG publication guidance note PM 32 available from HM Stationery Office. The ingress of moisture, dirt, vermin etc. into electrical equipment can cause malfunction and danger. Care should be taken to prevent such ingress whilst work is in progress, and covers should be replaced as soon as access to the chamber is no longer required. Before final closure of any compartment is effected, a careful inspection should be carried out to make sure no foreign matter or loose material is present. Before work is undertaken in any chamber containing high voltage conductors, tests using suitable voltage indicators should be carried out. These should include tests between .each phase and earth to ensure all conductors are dead. Voltage indicators should always be proved before and after use. When work is being carried out with adjacent pneumatically operated or air-blast circuit breakers in service, due precautions need to be taken to protect personnel from the effects of noise caused by these circuit breakers should they operate. Where circuit breakers are fitted with silencers, no problems should, occur but if they are unsilenced consideration should be given to the use of ear protectors. 2.3.5 Fire extinguishing equipment

All personnel carrying out maintenance on equipment where there is a fire risk or using flammable materials in processes requiring flame or other sources of heat should have fire fighting appliances available for ready use. These appliances may be installed permanently by an occupier or employer for use in the premises or they may be temporary appliances provided for the period of work. Employees should be trained in the use of portable appliances and know how to summon further assistance. If a fixed automatic fire extinguishing installation is installed, a prominent warning notice should be displayed at the entry to the protected area. The notice should Electrical test instruments Module 03 (Basic)

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also include instructions for preventing automatic operation when persons are working within the protected area. The prevention and restoration of automatic operation should be subject to appropriate safety procedures, for example by including a reference on the relevant permits to work. The type of fire extinguishers provided for use on or near electrical equipment should be compatible with the equipment and safe to use. Further advice on fire prevention and fire fighting may be obtained from the local Fire Prevention Officer. 2.3.6 Testing

2.3.6.1 General Care should be taken when applying test voltages to ensure that they are the lowest value required for the purpose with the minimum current output. Where equipment is capable of storing a charge this should be safely discharged after every test. NOTE 1: Further advice on electrical testing is available: one publication is Health and Safety Series Booklet No. HSG (13) 'Electrical testing' available from HM Stationery Office. NOTE 2: Electrical equipment may be damaged by the application of test voltages and currents of incorrect value and polarity. Some electronic equipment is particularly vulnerable (see clause 40). 2.3.6.2 Use of test instruments (oscilloscopes, etc.) Instruments should be of a type suitable for the measurements that are to be made so that a malfunction or the introduction of transients and/or reversed polarities into the connected circuits is avoided. The manufacturer's instructions should be observed. An earthed instrument lead may create danger if it is applied: to an active signal circuit which is normally floating. It is recommended that the instrument casings are earthed at all times but, where the nature of test precludes this, specific care should be taken by the operator to secure his own safety and that of others by the adoption of a safe system of work. It is recommended that suitably protected test leads be used at all times. 2.3.7 Disposal of scrap

Care is needed in the disposal of removed items or materials since some give rise to health or environmental danger unless properly handled, e.g. polychlorinated biphenols (PCBs) or asbestos. In case of doubt, reference should be made to the manufacturer's instructions or the appropriate local authority

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3.0.0 Multimeter A multimeter measures electrical properties such as AC or DC voltage, current, and resistance. Rather than have separate meters, a multimeter combines a voltmeter, an ammeter, and an ohmmeter. Electricians and the general public might use a multimeter on batteries, components, switches, power sources, and motors to diagnose electrical malfunctions and narrow down their cause. It is a black box of electronic circuitry that allows to troubleshoot just about any type of electrical wiring or device. Simply dial the proper function and scale, touch the two test leads to the wiring or device in question and check the meter reading. Depending on the setting, the multimeter will give indication to suggest a broken connection, no power, poor connections, faulty parts and more. The two main kinds of a multimeter are analog and digital. A digital multimeter has an LCD screen that gives a straight forward decimal read out, while an analog display moves a pointer through a scale of numbers and must be interpreted. Any multimeter will work over a specific range for each measurement. Select one that is compatible with what is required, from low-voltage power sources to high-voltage car batteries. Multimeters are specified with a sensitivity range, so make sure to choose the appropriate one. Multimeters are handheld devices. Analog multimeters are very cheap but sometimes difficult to read accurately, especially on resistance scales. Digital output devices are much easier to read but in general, cost more than analog meters. All multimeters will have a switch that allows to select the type of test or measurement to be performed. In addition, they always have two wires with metal tips called probes, one red and one black. As a voltmeter, a multimeter can measure the amount of AC or DC voltage flowing through a circuit. Voltage is a difference in potential energy between the two points. As an ohmmeter, a multimeter finds the resistance in a circuit, which is given in ohms. The multimeter actually passes a small amount of electricity from its own battery through the circuit to measure resistance by comparing the voltage sent out to what it receives. When used as an ammeter, the multimeter measures current flowing through a closed circuit by interrupting that circuit. The multimeter can only be connected in series, which means that all the circuit's current will flow through the ammeter's sensors

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3.1.0 Analog Multimeter

The permanent magnet moving coil analogue multimeters are based on the galvanometer invented by Arsene d’Arsonval. This device possesses a stationary permanent magnet, a moving coil, a spring, and a pointer attached to the coil. Figure below illustrates the way the equipment works. When a current flows through the coil, there is an induced force on it due to the created electromagnetic field, and the coil rotates around its central axis until the induced torque is equal and opposite to the spring torque. The rotation torque, and consequently the angle the pointer rotates is proportional to the current. The rotation angle is measured on a calibrated scale, and the amount of current flowing through the meter can be measured. The d’Arsonval movement is used

basically to measure average or DC currents and voltages By locating the range switch and the function switch in the proper position, the desired variable may be measured in the selected scale.

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3.2.0 Digital Multimeter

Figure shows a block diagram of an electronic digital multimeter. Note that the block diagram divides the instrument into three major sections: the SIGNAL CONDITIONING section, the ANALOG-TO- DIGITAL CONVERTER section, and the DISPLAY section. The signal conditioning section provides a dc analog voltage, characteristic of the applied input, to the analog-to-digital converter section. This task is accomplished by the input voltage divider, current shunts, ac converter, active filter, and associated switching. The analog-to-digital (a/d) converter section changes the dc output voltage from the signal conditioning section to digital information. The a/d converter uses a voltage-tofrequency conversion technique. A dc voltage at the input of the a/d converter is changed to a frequency by the analog integrated circuit (ic). This frequency is characteristic of the magnitude and polarity of the dc input voltage. Counting of the output frequency from the analog ic is accomplished by the digital ic. The resulting count is transferred in binary format to the display section. (Binary number systems are covered in NEETS, Module 13, Introduction to Number Systems, Boolean Algebra, and Logic Circuits.) The display section takes the digital (binary) information from the a/d converter section, decodes it, and visually displays it. The decoded digital information is displayed on numerical LED readouts

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3.2.1 Voltage Measurements

™

Plug the black test lead into the COM jack.

™

Plug the red test lead into the V jack.

™

Set the function/range switch to either DC volts in the upper left, or AC volts in the upper right.

™

If you do not know the approximate voltage about to be measured, use the largest voltage range available.

™

Connect the free ends of the red and black test leads ACROSS the device to the measured. Voltage is always measured with the meter in PARALLEL with the device.

™

If the LCD displays either "1." or "-1." with all other digits blank, the voltage is beyond the selected range. Use the switch to select a larger range.

™

Once you know the approximate voltage across the device, then use the switch to select the lowest voltage range that will still accommodate the voltage across the device. For example:

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3.2.2 Current Measurements

™ Turn the power off to the device and discharge any capacitors. ™ Plug the black test lead into the COM jack. ™ Plug the red test lead into either the 200 mA jack for small current measurements, or the 10 A jack for large current measurements. ™ If you do not know the approximate current about to be measured, use the 10 A jack. ™ Set the function/range switch to either DC amperes in the lower right, or AC amperes in the middle right. ™ Break open the circuit at the point where you want to measure the current by removing one of the wires. ™ Connect the free end of the red test lead to one place at which the wire was attached. ™ Connect the free end of the black test lead to the other place at which the wire was attached. ™ Current is always measured with the meter in SERIES with the device. ™ Using the current meter incorrectly will blow the fuse or damage the meter ™ Reapply the power to the device. ™ If the LCD displays either "1." or "-1." with all other digits blank, the current is beyond the selected range. Use the switch to select a larger range. ™ Once you know the approximate current through the device, then use the switch to select the lowest current range that will still accommodate the current through the device. ™ Turn the power off to the device before removing the meter from the circuit. 3.2.3 Resistance Measurements

™ Turn the power off to the device and discharge any capacitors! ™ Plug the black test lead into the COM jack. ™ Plug the red test lead into the V jack. ™ Set the function/range switch to ohms in the lower left. ™ If you do not know the approximate resistance about to be measured, use the largest range available. ™ Connect the free ends of the red and black test leads ACROSS the device to the measured. Resistance is always measured with the meter in PARALLEL with the device. ™ If the LCD displays either "1." or "-1." with all other digits blank, the resistance is beyond the selected range. Use the switch to select a larger range. Electrical test instruments Module 03 (Basic)

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™ Once you know the approximate resistance of the device, and then use the switch to select the lowest range that will still accommodate the resistance of the device. ™ Important note: The most common mistake when using a multimeter is not switching the test leads when switching between current sensing and any other type of sensing (voltage, resistance). It is critical that the test leads be in the proper jacks for the measurement you are making.

3.3.0 Digital vs. Analog Multimeters Digital multimeters have LCD readouts, do audible continuity testing. Some digital multimeters also feature auto-ranging and overload protection and other advantages analog multimeters lack. Analog multimeters have multiple scales on the dial , a moving needle and many manual settings on the function switch. It is a tricky spotting the correct scale to read on the dial, and sometimes have to multiply the reading by 10 or 100 to get your final value

3.4.0 Safety Precautions Be sure the test leads and rotary switch are in the correct position for the desired measurement. Never use the meter if the meter or the test leads look damaged. Never measure resistance in a circuit when power is applied. Never touch the probes to a voltage source when a test lead is plugged into the 10 A or 300 mA input jack. To avoid damage or injury, never use the meter on circuits that exceed 4800 watts. Never apply more than the rated voltage between any input jack and earth ground Be careful when working with voltages above 60 V DC or 30 V AC rms. Such voltages pose a shock hazard. Keep your fingers behind the finger guards on the test probes when making measurements. To avoid false readings, which could lead to possible electric shock or personal injury, replace the battery as soon as the battery indicator appears.

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4.0.0 Insulation resistance tester (Megohmmeter) The Insulation resistance tester (IRT) also known as a megohmmeter, is a portable instrument used to measure insulation resistance. It is a lightweight, simple and in minutes can help to determine the damaged installation. Checking the integrity of insulation is not only a good idea for a new installation, it’s a tremendous tool in ongoing maintenance, allowing to spot a problem wiring/equipment, before it creates arcing and damages the equipment or shuts everything down. The principle of operation of IRTs is as basic as Ohm’s Law: V=IR or R=V/I. The tester generates a known dc voltage (250 V, 500 V, 1k V or higher), chosen by the user, and measures the leakage current from the conductor through the insulation. The resistance is then calculated. The better the insulation, the lower the leakage current and the higher the amount of resistance present. For example, if 500 V is applied and 0.5 mA measured, then R=1 MΩ. If only one hundredth of that current, 5 μA, is measured, then R=100 MΩ The newest generation of IRTs is microprocessor-based and battery-powered. They are more precise than the older hand-cranked analog testers.

4.1.0 Analog Megohmmeter It consists of a hand-driven DC generator and a direct reading ohm meter. A simplified circuit diagram of this instrument is shown in Figure below.

The moving element of the ohm meter consists of two coils, A and B, which are rigidly mounted to a pivoted central shaft and are free to rotate over a C-shaped core. These coils are connected by means of flexible leads. The moving element may point in any meter position when the generator is not in operation. As current provided by the hand-driven generator flows through Coil B, the coil Electrical test instruments Module 03 (Basic)

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will tend to set itself at right angles to the field of the permanent magnet. With the test terminals open, giving an infinite resistance, no current flows in Coil A. Thereby, Coil B will govern the motion of the rotating element, causing it to move to the extreme counterclockwise position, which is marked as infinite resistance. Coil A is wound in a manner to produce a clockwise torque on the moving element. With the terminals marked "line" and "earth" shorted, giving a zero resistance, the current flow through the Coil A is sufficient to produce enough torque to overcome the torque of Coil B. The pointer then moves to the extreme clockwise position, which is marked as zero resistance. Resistance (R1) will protect Coil A from excessive current flow in this condition. When an unknown resistance is connected across the test terminals, line and earth, the opposing torques of Coils A and B balance each other so that the instrument pointer comes to rest at some point on the scale. The scale is calibrated such that the pointer directly indicates the value of resistance being measured.

4.2.0 Digital Megohmmeter There are an extensive and a versatile range of hand-held insulation testers designed to extend the capability of insulation testers beyond anything available on the market today. In addition to extremely high-sensitivity insulation resistance measurements (200 GΩ), these instruments offer complete multimeter testing capability and the ability to view the insulation measurement in terms of leakage current (µA). The top-of-the- range models also include data storage and download capability. The end user can now carry a single instrument to the test site rather than multiple instruments.

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Some of the common features are: ¾ Lightweight. Tough and robust ¾ Shrouded safety terminals with right angled test lead connector. ¾ Hands-free operation ¾ Voltage ranges of 250, 500, and 1000 V. ¾ Resistance measurement range of 200 GΩ ¾ Combined insulation & Continuity tester ¾ Default Voltmeter ¾ Battery condition test ¾ Automatic discharge of capacitive circuits after test ¾ Auto shut off Some of the top model’s advance features are: ¾ Auto ranging ¾ Selectable and programmable test voltage range (40 to 5000V) ¾ Automatic calculation of Polarisation Index(PI) ¾ Direct measurement and display of Capacitance & Leakage current ¾ Programmable test run time and PI ratio time ¾ Automatic test inhibition (if live sample > 25V) ¾ RS-232 interface for direct printing of results

¾ 128 kB memory for storing field test data ¾ Software for data storage, real time display analysis and report generation

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4.3.0 Insulation resistance test Insulation resistance tests give an indication of the condition of insulation, particularly with regard to moisture and dirt. The actual value of the resistance varies greatly in different types of machines, depending on the type, size, voltage rating, etc. The principal worth of such measurements, therefore, is in the relative values of insulation resistance of the same apparatus taken under similar conditions at various times. Such tests usually reveal how well the machine has been maintained. Measuring insulation resistance is rather straightforward. Identify any two points between which there is insulation and make a connection with a megohmmeter. Take a measurement; the measured value represents the equivalent resistance of all the insulation that exists between the two points and any component resistance that might also be connected between the two points.

Megohmmeters are available in several varieties. Some are powered by a handcranked generator, while others are battery powered. Some use power supply voltages as low as 50V, but the most common is 50OV, with some going as high as 10,OOOV. The power supply, in all cases, is DC. 4.3.1 Components of DC leakage current

When a megohm. test is made, three components of current flow. The insulation between the two connection points can be thought of as a dielectric, thus forming a capacitance. A phenomenon known as “dielectric absorption” occurs whereby the dielectric soaks up current and then releases it when the potential is removed. This is in addition to the current that charges and discharges the capacitance, and it occurs much more slowly. It is dependent on the nature of the dielectric. Two types of items where this is of concern are capacitors and motors. Such current is referred to as dielectric absorption current. The current required to charge whatever capacitance is present is known as “charging current” Like the dielectric absorption current, it decays exponentially to zero, Electrical test instruments Module 03 (Basic)

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but much more quickly. It is this current which in most cases determines how long it takes to make an accurate megohm measurement. When the reading appears to stabilize, it means that the charging current has decayed to a point where it is negligible with respect to the leakage current. The current that flows through the insulation is the leakage current. The voltage across the insulation divided by the leakage current through it equals the insulation resistance. Thus, to accurately measure insulation resistance, we must wait until the dielectric absorption current and the charging current have decayed to the point where they are truly negligible with respect to the leakage current.

The total current that flows is the sum of the three components just mentioned. It decays exponentially from an initial maximum and approaches a constant value which is the leakage current alone. The megohm reading is dependent on the voltage across the insulation and the total current. It increases exponentially from an initial 4.3.2 Determining The Polarization Index

Knowing the polarization index of a motor, generator or transformer can be useful in appraising the fitness of the machine for service. The index is calculated from measurements of the winding insulation resistance. Before measuring the insulation resistance, remove all external connections to the machine and completely discharge the windings to the grounded machine frame. Proceed by applying either 50OVDC or 1,OOOVDC between the winding and ground using a direct-indicating, power-driven megohmmeter. For machines rated 500V and over, the higher value is used. The voltage is applied for 10 minutes and kept constant for the duration of the test. The polarization index is calculated as the ratio of the 10-minut value to the oneminute value of the insulation resistances measured consecutively: Electrical test instruments Module 03 (Basic)

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Polarization index = resistance after 10 minutes resistance after one minute The recommended minimum value of polarization index for AC and DC motors and generators is 2.0. Machines having windings with a lower index are less likely to be suited for operation.

The polarization index is useful in evaluating windings for: ¾ Buildup of dirt or moisture ¾ Gradual deterioration of the insulation (by comparing results of tests made earlier on the same machine) ¾ Fitness for overpotential tests ¾ Suitability for operation 4.3.3 Correction for Winding Temperature

One important point to remember is that the value of insulation resistance decreases as the temperature of the insulation increases. This is just the opposite of the effect for conductor resistance. In order to gather meaningful information that can be used for comparison purposes, we should ideally carry out periodic tests with the winding at the same temperature conditions. If this is not possible, it is necessary to measure the actual temperature of the winding under test and then correct the resistance reading to a o

standard temperature, usually 20 C. If we measured the insulation resistance to be, say 100 MW at a temperature of o

30 C, we should multiply the result by the correction factor of 1.98 shown on the chart o

below. This implies that at a temperature of 20 C the insulation resistance would increase to 198 MW. These correction factors will normally be provided by the equipment manufacturer. The main point here is that all readings, past, present and future should be compared on the same basis Electrical test instruments Module 03 (Basic)

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4.3.4 Insulation Contamination

In order to obtain reliable test figures, windings should be free of dirt and moisture as both of these contaminants result in a lower value of resistance being indicated. If a machine has recently been taken out of service, it is likely to be hot and therefore free from moisture. However, the windings may be quite dirty from dust and oil in the atmosphere. Conversely, if the machine has been out of service for some time, the winding insulation may well have absorbed a certain amount of moisture. Indeed, if the insulation resistance is indicated as low, it may be necessary to dry out the windings. All of these items must be taken into consideration when assessing the reliability of insulation resistance readings

4.4.0 Insulation resistance test methods When testing the insulation resistance in electrical equipment, any of the following methods can be employed. ¾ Spot reading ¾ Step voltage ¾ Time resistance test Testing insulation in electrical systems is a critical step improving safety and longer system life. 4.4.1 Spot testing

This is a short time resistance test. The megohmmeter is connected directly across the equipment being tested and a test voltage is applied for about 60 secs. In order to get a stable insulation resistance reading in that time, the test is performed on low capacitance equipment. This is a simple and quick test to indicate the instantaneous condition of insulation. Mostly used as part of the commissioning process for a new installation. Electrical test instruments Module 03 (Basic)

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4.4.2 Step voltage test

Various test voltage in steps of (in increasing order), usually for the same period of time (60 Secs). The insulation values are recorded on the graph. The insulation is exposed to increased electrical stress that can reveal information about flaws in the insulation such as pinholes, physical damage or brittleness. 4.4.3 Time resistance test

This test is carried out to compare the absorption characteristic of contaminated insulation with the absorption characteristic of good insulation. The test voltage is applied for the 10 mins and after every 10 secs the data is recorded for first one minute and then after every one minute. The interpretation of the slope of the plotted graph determines the condition of the insulation. The polarisation index is another test in this category for determining the quality of insulation. This is discussed in earlier part of this chapter.

4.5.0 Safety Precautions ™ Be sure the test leads and rotary switch are in the correct position for the desired measurement. ™ Never use the meter if the meter or the test leads look damaged. ™ Never measure insulation resistance in a energised circuit. ™ Make sure that the systems under test have been completely discharged to ground. ™ Never touch the probes to a voltage source when a testing is in progress ™ Test voltage should not exceed the equipment manufacturer’s recommended voltage for insulation testing. ™ Ensure that equipment under test is discharged to ground after the test, if the equipment do not have auto discharge feature ™ Be careful when working with voltages above 60 V DC or 30 V AC rms. Such voltages pose a shock hazard. ™ Keep your fingers behind the finger guards on the test probes when making measurements. ™ To avoid false readings, which could lead to possible electric shock or personal injury, replace the battery as soon as the battery indicator appears.

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4.6.0 Insulation resistance (IR) test on Cables Prior to testing required permits must be secured. All safety precautions should be observed while testing. Cable must be discharged and disconnected form the equipment in the field. IR should be measured as illustrated in the figure below:

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4.7.0 Insulation resistance (IR) test on Transformer Prior to testing required permits must be secured. All safety precautions should be observed while testing.

4.8.0 Insulation resistance (IR) test on Motor/Generator Prior to testing required permits must be secured . All safety precautions should be observed while testing The easiest test that prevents the most failures is the “insulation resistance measurement”, It applies DC voltage, usually 500 or 1000 volts, to the motor and measures the resistance of the insulation between the windings and earth (frame). Before testing the motor or Generator lift the rotor brushes (whereever applicable), earth the stator terminals, frame and shaft. Discharge the field winding by earthing. Then remove the field winding from earth and measure the field winding insuation to earth. A minimum resistance to earth at 40 degrees C ambient of 1 megohm per kV of rating plus 1 megohm may be acceptable. Medium size motors in good condition will generally have megohmmeter readings in excess of 50 megohms. Low readings may indicate a worse condition of insulation caused by contamination from moisture, oil or conductive dirt or deterioration from age or excessive heat.

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Measuring insulation resistance is rather straightforward. Identify any two points between which there is insulation and make a connection with a the test instrument is often referred to as a Megger, after the manufacturer’s trademark. Take a measurement; the measured value represents the equivalent resistance of all the insulation that exists between the two points and any component resistance that might also be connected between the two points.Megger s are available in several varieties. Some are powered by a hand-cranked generator, while others are battery powered. Most common is 500V output, with some going as high as 10,000V. The power supply, in all cases, is DC.

TE ST 1kV 500V 250V

MΩ

100V 50V O FF V ΩΩ

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IR measurement on Cage type Induction motor

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5.0.0 Clamp on meter A clamp meter (clamp-on ammeter) is a type of ammeter which measures electrical current without the need to disconnect the wiring through which the current is flowing.

Clamp meters are also known as tong testers or Amprobes (after Amprobe Instrument Company, one of the first vendors of such devices). The most common forms of clamp meter are: ™ A probe for use with a multimeter. ™ A self-contained unit. ™ A built-in part of a specialised multimeter used by electricians.

In order to use a clamp meter, the probe or clamp is opened to allow insertion of the wiring, and then closed to allow the measurement. Only one conductor is normally passed through the probe, if more than one conductor were to be passed through then the measurement would be a vector sum of the currents flowing in the conductors and could be very misleading depending on the phase relationship of the currents. In particular, if the clamp were to be closed around a mains extension or similar cord, no current will be measured at all as the current flowing in one direction will cancel that flowing in the Electrical test instruments Module 03 (Basic)

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other direction. Only one (1) conductor can be measured at a time, and the cable can either be bare or insulated. The current in the conductor to be measured is (carefully) segregated from other current-carrying conductors, and shifted enough so that the jaws of the clampon ammeter can be opened, slipped around the cable, and then closed. As soon as the jaws close, a clear and accurate reading is registered on the scale. The jaws are insulated, and the Bakelite handle and shield protect the technician from shock.

5.1.0 Theory of operation of AC Clamp on meter The meter is operated by the magnetic field set up by the current. Basic construction of the meter is a clamp on current probes and the ammeter (Analog or digital) connected to it.

The clamp on current probe works on the principle of current transformer. The conductor is the primary coil of a current transformer The clamp on probe are composed of permalloy split core with the winding coil which connects to the meter (Analog or digital) circuit. First the conductor current determines the strength of the magnetic field around the permalloy core. Then at the end of the winding, the magnetic field induces secondary out-put which drives the current. through the meter (Analog or digital) connected. The meter is calibrated to indicate the current in the primary. A clamp-on current probe, shown in the above diagram, converts the primary current of the conductor to a current output whose value depends on number of turns of secondary winding (N2). If N2 is 1000 turns, the output current is 1/1000 of the primary current, which can be expressed as 1 Milliampere per Ampere. Such a clamp is referred to as having a ratio of 1000:1. The output of this current clamp can be read by any AC ammeter (Analog or digital) whose input impedance is compatible with the specifications of the current clamp.

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5.2.0 Theory of operation of AC/DC Clamp on meter More modern designs of clamp-on ammeters utilize a small magnetic field detector device called a Hall-effect sensor to accurately determine field strength. The two matched sensors provide an output signal which is independent of the location of the current conductor in the clamp opening. The conductor does not have to be exactly at the center of the opening. A battery-operated circuit is required to provide the excitation and amplification of the signal generated by the HALL-EFFECT sensor

Hall effect principle : AC/DC current sensing is achieved by measuring the strength of the magnetic field created by a current carrying conductor in a semiconductor chip using Hall effect principle. When a thin semiconductor is placed at right angle to a magnetic field (B), and a current (Id) is applied to it, a voltage (Vh) is developed across the semiconductor. This voltage is known as the Hall voltage, named after the US scientist Edwin Hall.

When the Hall device drive current is held constant, the current is directly proportional to the current in a conductor. Thus, the hall output voltage (Vh) is representative of that current.

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Some clamp-on meters contain electronic amplifier circuitry to generate a small voltage proportional to the current in the wire between the jaws, that small voltage connected to a voltmeter for convenient readout by a technician. Thus, a clamp-on unit can be an accessory device to a voltmeter, for current measurement.

5.3.0 Specifications of Digital Clamp on meters ™ AC Current : It is the measuring value of the alternating current taken by the load of a clamp on meter ™ AC Voltage : It is defined as the alternating voltage measured by the clamp on meter. ™ DC Current : It is the measuring value of the direct current read by the clamp on meter ™ DC Voltage : It is defined as the direct voltage measured by the clamp on meter ™ Resistance : It is the resistance offered by the clamp on meter to the current flow ™ Frequency range : It is the range of frequency at which the current or voltage is measured. ™ Distortion factor : It is defined as a measure of non linear distortion. ™ Total harmonic distortion : It is defined as the ratio of the sum of the powers of all harmonic frequencies above the fundamental frequency to the power of the fundamental frequency. It is usually referred to as THD. THDandis measured in dB ™ Display type : It is the type of electronic display where the measured values are monitored and graphed. ™ Crest factor : It is the ratio of the peak amplitude value to its RMS value. ™ Clamp jaw size : It refers to the diameter value of the opening jaw.

5.4.0 Advantages of Digital Clamp on meter ™ Fast measurements ™ Precise measurement ™ Less meter loading

5.5.0 Advantages of Digital over Conventional Type Digital clamp on meters are more advantageous than the conventional clampmeters. Because in the conventional type, the current wave obtained is of sinusoidal nature. The current value is measured generally in RMS units. If these factors are not

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taken into consideration, it is of less use with non sinusoidal load applications such as fluorescent lamps, modern computers, electronic equipment, or high-intensity discharge lamps.

5.6.0 Applications of Digital Clamp on meters ™ Motor drives ™ Electric vehicles ™ Electricity supply industry(ESI) ™ Automotive diagnostic plants ™ Electrochemical plants ™ Power supplies ™ Welding equipment

5.7.0 Clamp on meter operations (Fluke model 321/322)

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5.8.0 Safety Precautions To avoid possible electric shock or personal injury, and to avoid possible damage to the Meter or the equipment under test, adhere to the following practices: ™ Avoid working alone as far as possible, and render the assisstance. ™ Never use the Meter on a circuit with voltages higher than specified. ™ Never use the Meter on a circuit with frequency higher than specified, the meter could be damaged. ™ Do not use the Meter or test leads if they look damaged. ™ Use extreme caution when working around bare conductors or bus bars. Contact with the conductor could result in electric shock. ™ Read the manufacturer’s instructions and safety sheet before use and follow all safety instructions. ™ Use the Meter only as specified in the instruction manual; otherwise, the Meter’s safety features may be impaired. ™ Use caution when working with voltages above 60 V dc or 30 V ac. Such voltages pose a shock hazard.

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™ Before using the Meter, inspect the case. Do not use the Meter if it is damaged. Look for cracks or missing plastic. Pay particular attention to the insulation around the connectors. ™ Verify the Meter’s operation by measuring a known current/voltage. Do not use the Meter if it operates abnormally. Protection may be impaired. When in doubt, have the Meter serviced. ™ Do not apply more than the rated current or voltage, as marked on the Meter. ™ Use the proper terminals, function, and range for your measurements. ™ Do not operate the Meter with the case (or part of the case) removed. ™ When servicing the Meter, use only replacement parts recommended by the manufacturer.

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6.0.0 Earth tester, Loop tester & Residual Current Device (RCD) tester A practical earth electrode that provides a low ground resistance is not always easy to obtain. The metallic body in the earth is often referred to as an electrode even though it may be a water-pipe system, buried strips or plates, or wires. Such combinations of metallic bodies are called a grid. The earth resistance is the resistance to current from the electrode into the surrounding earth. To appreciate why earth resistance must be low, you need only use Ohm’s Law: E = R x I where E is volts; R, the resistance in ohms; and I, the current in amperes. Assume that you have a 4000-V supply (2300 V to ground) with a resistance of 13 Ω (see Fig. below). Now, assume that an exposed wire in this system touches a motor frame that is connected to a grounding system which has a 10-ohm resistance to earth.

By Ohm’s Law, there will be a current of 100 A through the fault (from the motor frame to the earth). If someone happen to touch the motor frame and are grounded solidly to earth, could be subjected to 1000 V (10 Ω x 100 A). This may be more than enough to kill a person instantly. If, however, the earth resistance is less than 1 Ω, the shock person would get could be under 100 V (1 x 100) and probably survive that shock. Earth resistivity has an important bearing on electrode resistance, as does the depth, size and shape of the electrode. In this module, the principles and method of testing and use of earth resistance tester are covered. This applies to lightning arrester installations as well as to other systems that require low resistance ground connections. Such tests are made in power-generating stations, electrical-distribution systems, industrial plants, and telecommunication systems. Also an Earth loop impedance testing is essential since if a live conductor is accidentally connected to an earth conductor in a faulty appliance or circuit, the resulting short-circuit current to earth can easily be high enough to cause electric shock or generate enough heat to start a fire. Normally, the fuse will blow or another circuit protection device will trip, but a situation may arise where the actual short-circuit current in a faulty Electrical test instruments Module 03 (Basic)

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installation is of insufficient level and the protection device would thus take too long to activate. The delay can be disastrous for life and property. It is therefore necessary to know if the impedance of the path that any fault current would take is low enough to allow sufficient current to flow in the event of a fault and that any installed protective device will operate within a safe time limit. The earth loop impedance of each individual circuit a path from the point of use back to the incoming supply connection point. As measurement of circuit loop impedance is made with the supply normally on, precautions must be taken to avoid the possibility of electric shock and danger to personnel working in the vicinity of the circuit under test. In IEC 60364, fault loop testing falls under the category of ‘Verifying protection by automatic supply disconnection’. This covers verification of the effectiveness of protective measures (such as test on RCD), and the test methods applied to measure the fault loop impedance. Conventional techniques for measuring loop impedance can often trip RCDs, preventing further measurement. Often the only way around this is to “bridge” the RCD or replace the RCD with an equivalent rated MCB for the duration of the test – both of which are potentially dangerous and time consuming practices. To overcome this manufacturer’s of earth loop tester have applied innovative technology to ensure that both electromechanical and electronic type RCDs do not trip during earth loop impedance measurements. An advanced range of combined loop and RCD testers is available and it is designed to fully test RCDs and measure loop impedance and prospective short circuit current, (PSCC), on single and three phase systems rated up to 300V ac r.m.s. to earth.

6.1.0 Earth resistance Resistance to current through an earth electrode actually has three components. 1. Resistance of the electrode itself and connections to it. 2. Contact resistance between the electrode and the soil adjacent to it. 3. Resistance of the surrounding earth. Electrode Resistance: Rods, pipes, masses of metal, structures, and other devices are commonly used for earth connections. These are usually of sufficient size or crosssection that their resistance is a negligible part of the total resistance. Electrode-Earth Contact Resistance: This is much less than you might think. If the electrode is free from paint or grease, and the earth is packed firmly, contact resistance is negligible. Rust on an iron electrode has little or no effect; the iron oxide is readily soaked with water and has less resistance than most soils. But if an iron pipe has Electrical test instruments Module 03 (Basic)

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rusted through, the part below the break is not effective as a part of the earth electrode. Resistance of Surrounding Earth: An electrode driven into earth of uniform resistivity radiates current in all directions. Think of the electrode as being surrounded by shells of earth, all of equal thickness. The earth shell nearest the electrode naturally has the smallest surface area and so offers the greatest resistance. The next earth shell is somewhat larger in area and offers less resistance. Finally, a distance from the electrode will be reached where inclusion of additional earth shells does not add significantly to the resistance of the earth surrounding the electrode. It is this critical volume of soil that determines the effectiveness of the ground electrode and which therefore must be effectively measured in order to make this determination. Ground testing is distinct when compared to more familiar forms of electrical measurement, in that it is a volumetric

measurement and cannot be treated as a “point” property. Generally, the resistance of the surrounding earth will be the largest of the three components making up the resistance of a ground connection. The several factors that can affect this value such as the soil material, the moisture content, and the temperature. It is far from a constant, predictable value ranging generally from 500 to 50,000 ohm-cm3

6.2.0 Principle of Earth resistance testing The resistance to earth of any system of electrodes theoretically can be calculated from formulas based upon the general resistance formula:

Where ρ is the resistivity of the earth in ohm-cm, L is the length of the conducting path, and A is the cross-sectional area of the path. More complex formulas for the calculation of the resistance to earth for any distance from various systems of electrodes are drived. All such formulas can be simplified a little by basing them on the assumption that the earth’s resistivity is uniform throughout the entire soil volume under Electrical test instruments Module 03 (Basic)

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consideration. Because the formulas are complicated, and earth resistivity is neither uniform or constant, a simple and direct method of measuring earth resistance is needed. This is where Earth Resistance Tester, a self-contained portable instrument is used. This test instrument is reliable and easy to use. With it, one can check the resistance of the earth electrode while it is being installed; and, by periodic tests, observe any changes with time. To understand the principle of earth testing, consider the schematic diagram in Fig. below. As explained earlier with the earth shell diagram, with increased distance from an electrode, the earth shells are of greater surface area and therefore of lower resistance. Now, assume that there are three rods driven into the earth some distance apart and a voltage applied, as shown in Fig. The current between rods 1 and 2 is measured by an ammeter; the potential difference (voltage) between rods 1 and 3 is measured by a voltmeter.

If rod 3 is located at various points between rods 1 and 2, preferably in a straight line, a series of voltage readings are obtained. By Ohm’s Law (R = E/I) the earth resistance at any point could be calculated. For example, if the measured voltage E between rods 1 and 3 is 30 V and the measured current I is 2 A, the resistance of the earth R at that point would be 15 Ω.

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The series of resistance values can be plotted against distance to obtain a curve as shown in Fig. below. Note that as rod 3 is moved away from rod 1, the resistance values increase, but the amount of increase gets less and less until a point is reached where the rate of increase becomes so small that I can almost be considered constant (20 Ω in Fig.). The earth shells between the two rods (1 and 3) have so great a surface area that they add little to the total resistance. Beyond this point, as rod 3 approaches the earth shells of rod 2, resistance gradually picks up. Near rod 2, the values rise sharply. Now, let’s say that rod 1 is the earth electrode under test. From a typical earthresistance curve, such as Fig. above, what is the resistance to earth of this rod? We call rod 2 current-reference probe “C” and rod 3, potential reference probe “P” (simply for convenience in identification). The correct resistance is usually obtained if P (rod 3) is placed at a distance from the center of the earth electrode (rod 1) about 62 percent of the distance between the earth electrode and C (rod 2). Finally, rod C should be far enough away from the earth electrode system so that the 62 percent distance is out of the “sphere of influence” of the earth electrode. For the test, the electrode should be isolated from the electrical system that it is protecting; otherwise, the whole system is tested which (depending on local practices) may include the pole ground, system neutral, and transformer ground. This obscures the specific effect of the local ground.

6.3.0 Earth resistance test methods There are three basic test methods as noted below. 1. Fall-of-potential method, or three-terminal test. 2. Dead Earth method (two-point test). 3. Clamp-on test method. In PGB-POD mostly the “fall of potential is used”.Therefore this method is explained in the following para. The earth tester generates an a.c. signal which is fed into the system under test. The instrument then checks the status of the circuits for good connection and noise. If either of these variables is out of specification then the operator is informed. Having checked that the conditions for test are met, the instrument automatically steps through its measurement. ranges to find the optimum signal to apply. Measuring the current flowing and the voltage generated the instrument calculates and displays the system resistance in the range of 0.001 to 20,000 ohms, depending on the instrument specification chosen. With a four-terminal tester, P1 and C1 terminals on the instrument are jumpered and connected to the earth electrode under test. With a three-terminal instrument, connect Electrical test instruments Module 03 (Basic)

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X to the earth electrode. it may be better to use all four terminals by a lead from the P1 terminal to the test electrode (connecting it inside the lead from C1). This is a true four wire test configuration which eliminates all lead resistance from the measurement. The driven reference rod C should be placed as far from the earth electrode as practical; this distance may be limited by the length of extension wire available, or the geography of the surroundings. Leads should be separated and not run close and parallel to each other, to eliminate mutual inductance.

Potential-reference rod P is then driven at mid point on a straight line between the earth electrode (X) and C. The subsequent two readings are taken moving the rod P closer to the earth electrode, say 1 meter and away from the earth electrode by same distance (1 meter). Resistance readings are logged for each of the points and average of the readings are taken, if the three readings do not differ from each other (within 5%) by large margin. Otherwise, the rod C has to be driven further away from earth electrode and the procedure is to be repeated.

6.4.0 Earth Loop resistance The main purpose of good earth connections and a low resistance earth path in a wiring installation is to allow sufficient current to flow in the event of a fault to operate circuit protective devices, i.e. fuses and circuit breakers. If the resistance of any part of an earth loop is high, the protective circuit may be rendered useless because the current which will flow in the event of a fault may be insufficient to operate the protection. In the event of a fault under these conditions not only may the faulty circuit remain energised but the fault current will find an alternative path where possible. This may result in damage to electrical equipment or installations or pose severe, or even fatal, shock risk to persons in contact with the faulty equipment, since the fault current will pass through them. An earth fault loop, also known as phase-earth loop or line-earth loop, consists of the circuit protective conductor; the installation earthing terminal and earthing conductor; Electrical test instruments Module 03 (Basic)

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the earth return path back to the supply transformer and its winding; the phase conductor back to the point of the fault.

6.5.0 Earth Loop resistance test An earth fault loop test on an installation is performed by switching a known low value of resistance between the phase and earth conductors at the desired point test and measuring the voltage drop across the resistance. In effect this is simulating a fault between phase and earth and calculation made around the supply voltage and voltage drop across the test resistor enable the earth fault loop impedance to be indicated. The same tester may also be used for the determination of prospective earth fault current, which is the maximum current able to flow in a phase-earth fault in an installation, and they may also be used to indicate the prospective short circuit current which is the maximum current able to flow in the event of a phase-neutral fault. The earth loop testers available in the market, offer both traditional measuring techniques and state of the art "non-RCD Tripping" technology.

6.6.0 Digital Earth Loop resistance tester from Megger (L T5 and L T6) The MEGGER@ L T5 and L T6 Digital Loop Testers have been designed for quickly, accurately and reliably testing newly established and existing wiring installations. They are simple to use, both with the standard lead for socket tests and with the optional safety leads for performing tests on lighting installations and testing earth

bonding. The L T5 has two measuring ranges: 20 Ω with a resolution of 0.01 Ω and 200 Ω with a resolution of 0,1 Ω. The L T6 also has two ranges: 20 Ω with a resolution of 0.01 Ω and 2000 Ω with a resolution of 1 Ω. Both instruments will operate on installations with a phase-to-neutral voltage 230

Electrical test instruments Module 03 (Basic)

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V a.c. ± 10% and automatically compensate for supply variations. The test current, up to 25 A, is dependent on the impedance of the phase-earth loop being measured and flows for two half cycles of the supply voltage. The circuit is fuse protected and fitted with an internal thermal switch to prevent excessive heating caused by tests repeated too frequently. Testing is very simple as there is no initial setting up to be done and no pushbutton to operate. A test is automatically executed in about 4 seconds after the selector switch is set to a measuring range and connection made to the circuit under test. (Either step may be performed first.) Neons illuminate to show that there are no open circuits in the installation wiring and that a correct phase conductor connection exists. If the earth connection is not present, the test will not be performed. Use of a large, 3½ digit L.C.D. makes measurement readings easy with less chance of ambiguity. It also results in a much more rugged and robust test instrument that, because of its strong plastic case, will withstand the rough treatment expected of an installation engineer's tool. The lightweight, hand-held tester also incorporates a fold-away support stand/suspension hook for use when the operator requires both hands for using the "flying leads".

6.7.0 Applications & Use of Earth Loop resistance tester

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Electrical test instruments Module 03 (Basic)

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6.8.0 Residual Current devices (RCDs) Increasingly in modern installations, earth leakage circuit breakers are used to provide protection in additional to conventional fuses and circuit breakers. These devices are referred to by a variety of different names including RCD (Residual Current Device), RCCB (Residual Current Circuit Breaker), ELCH (Earth Leakage Circuit Breaker) and GFI (Ground Fault Interrupt), to name but a few. The devices operate by sensing when the current in the phase and neutral conductors within an installation are not equal and opposite. Any imbalance would imply that an additional path existed for the flow of current, invariably through the earth due to excessive leakage and/or a fault situation.

6.9.0 Testing of RCDs RCDs can be tested to see if they are operational and/or they have been wired correctly. It is a good idea to check RCDs monthly. One way to test an RCD is to press the button labelled "Test" or "T" on the RCD unit (which will simulate a ground fault by bypassing some current) and see if the RCD reacts by correctly opening the circuit. If it does not trip, the RCD should be replaced. Unfortunately, the test button is a fairly crude test and it is quite possible (though rare) for an RCD to trip on the pressing of the test button even when it would not pass a proper test involving passing known leakage currents and measuring the resulting trip time (and comparing those values to the requirements given in a standards document such as BS 7671). For example, an incorrectly wired RCD may still trip when the test button is Electrical test instruments Module 03 (Basic)

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pressed even though a real ground fault may not cause it to trip. RCD testers are designed to simulate a range of fault currents, with restrictions on the duration of the fault current, and to time the operation of the device. This will indicate the ability of the RCD to interrupt a particular fault current within time certain limits to ensure protection against fire, damage and electrocution.

6.10.0 Digital RCD tester from Megger (CBT3 and CBT4) The CBT3 and CBT4 are hand-held instruments for testing residual current protective devices (RCDs) in wiring installations. The instruments are connected through a normal mains socket outlet or directly via the RCDs terminals. Neon lamp indicate if there are no open circuits in the installation and if the phase connections are correct. A rotary switch selects the RCD rating from one of six values available and a

membrane push-button is pressed to execute a test. A known fixed current, determined by the type of test selected, flows to earth in the installation the RCD is protecting, for a given length of time. The types of test available are: (i) a 'no trip' test carried out at half the rating selected, the result of which should be that the device under test does not trip. (ii) a 'trip' test carried out at the rating selected, the result of which should be that the device trips within the time specified for that particular design of breaker (iii) a test carried out at 150 mA and designed for testing devices (up to 30 mA rating) fitted to protect against direct contact with the installation. The result should be that the device trips within 40 ms. (iv) a test carried out at five times the rating selected, the result of which should be that the device trips within 40 ms. Electrical test instruments Module 03 (Basic)

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Membrane push-buttons are used to select the type of test. The 'ABC' key selects type of breaker to be tested. The phase key selects the point on the a.c. waveform from where the test will start, i.e. the positive or negative zero crossing point. The 'I' key, will allow one of three current multipliers or a 150 mA specific test to be selected. The test key will initiate a test. The 4 digit LCD shows the time value that the RCD takes to trip. For a successful 'no trip' test the maximum time of test current flow is given. For unsuccessful tests on 'B' and 'C' type devices the display shows the word 'FAIL' as the test result. The instrument circuit is microprocessor controlled and will always assume the default setting when switched on or when the rotary switch is moved out of the stand-by position. The maximum current that can flow is 500 mA. The instrument has a thermal cut out to prevent overheating caused by rapidly repeated tests at high current. Also, it is hardware and software protected against hazardous live voltages. If in the event prior to a test the earth neutral potential is greater than 50 V,' or a test current causes earth potential to rise greater than 50 V above neutral, the instrument will then turn the test current off within 40 ms and show >50 V on the display. The rotary switch has a 'Standby' position which, when selected (with the instrument connected to the supply), renders the LCD blank but the microprocessor in the reset state.

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6.11.0 Safety Precautions There is an inherent safety problem in earth resistance testing that requires care and planning by the user of the earth resistance test set. The possibility exists that a fault in the power system will cause a high current to flow into the ground system while the test is in progress. This may cause unexpected high voltages to appear at the current and voltage probes and also at the terminals of the test set. This risk must be evaluated by the person responsible for the tests, taking into account the fault current available and expected step-and-touch potentials. IEEE Standard 80 entitled “IEEE Guide for Safety in AC Substation Grounding” fully covers this subject. It is recommended that the operator should wear rubber protective gloves while handling connections and use a rubber safety mat while operating the earth resistance test set. Following safety precautions must be taken before and while performing the earth loop impedance test or testing RCD. ™ Safety Warnings and Precautions recommended by manufacturer must be read and understood before the instrument is used. They must be observed during use. ™ Continuity of protective conductors and earthed equipotential bonding of new or modified installations must be verified before carrying out RCD tests, or earth fault loop impedance tests. ™ Do not leave the instrument connected to the mains supply when not in use. ™ Circuit connections and exposed metalwork of an installation or equipment under test must not be touched. ™ Ensure that hands remain behind guards of probes/clips when testing. ™ The instrument should not be used if any part of it is damaged. ™ Test leads, probes and crocodile clips must be in good order, clean and with no broken or cracked insulation. ™ The battery cover must be in place whilst conducting tests. ™ Voltage indicator LED’s cannot reveal a N-PE supply reversal. ™ National Safety Authorities may recommend the use of fused test leads when measuring voltage on high-energy systems. ™ When making a 2 wire measurement with the 3 wire lead set, for safety reasons the black test lead should be connected together with the green test. Electrical test instruments Module 03 (Basic)

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7.0.0 Attachments 7.1.1 Fluke multimeter manual 7.12 Megger Manual BM80 7.13 Fluke Clamp on meter Instruction sheet 7.14 Megger Digital Earth Tester 7.15 Megger Digital Loop Tester 7.16 Megger RCD Tester

Electrical test instruments Module 03 (Basic)

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®

80 Series III Multimeters

Users Manual

October 1997 Rev.4, 6/02 1997-2002 Fluke Corporation, All rights reserved. Printed in U.S.A. All product names are trademarks of their respective companies.

Lifetime Limited Warranty Each Fluke 20, 70, 80, 170 and 180 Series DMM will be free from defects in material and workmanship for its lifetime. As used herein, “lifetime” is defined as seven years after Fluke discontinues manufacturing the product, but the warranty period shall be at least ten years from the date of purchase. This warranty does not cover fuses, disposable batteries, damage from neglect, misuse, contamination, alteration, accident or abnormal conditions of operation or handling, including failures caused by use outside of the product’s specifications, or normal wear and tear of mechanical components. This warranty covers the original purchaser only and is not transferable. For ten years from the date of purchase, this warranty also covers the LCD. Thereafter, for the lifetime of the DMM, Fluke will replace the LCD for a fee based on then current component acquisition costs. To establish original ownership and prove date of purchase, please complete and return the registration card accompanying the product, or register your product on http://www.fluke.com. Fluke will, at its option, repair at no charge, replace or refund the purchase price of a defective product purchased through a Fluke authorized sales outlet and at the applicable international price. Fluke reserves the right to charge for importation costs of repair/replacement parts if the product purchased in one country is sent for repair elsewhere. If the product is defective, contact your nearest Fluke authorized service center to obtain return authorization information, then send the product to that service center, with a description of the difficulty, postage and insurance prepaid (FOB Destination). Fluke assumes no risk for damage in transit. Fluke will pay return transportation for product repaired or replaced in-warranty. Before making any non-warranty repair, Fluke will estimate cost and obtain authorization, then invoice you for repair and return transportation. THIS WARRANTY IS YOUR ONLY REMEDY. NO OTHER WARRANTIES, SUCH AS FITNESS FOR A PARTICULAR PURPOSE, ARE EXPRESSED OR IMPLIED. FLUKE SHALL NOT BE LIABLE FOR ANY SPECIAL, INDIRECT, INCIDENTAL OR CONSEQUENTIAL DAMAGES OR LOSSES, INCLUDING LOSS OF DATA, ARISING FROM ANY CAUSE OR THEORY. AUTHORIZED RESELLERS ARE NOT AUTHORIZED TO EXTEND ANY DIFFERENT WARRANTY ON FLUKE’S BEHALF. Since some states do not allow the exclusion or limitation of an implied warranty or of incidental or consequential damages, this limitation of liability may not apply to you. If any provision of this warranty is held invalid or unenforceable by a court or other decision-maker of competent jurisdiction, such holding will not affect the validity or enforceability of any other provision.

2/02

Fluke Corporation

Fluke Europe B.V.

P.O. Box 9090

P.O. Box 1186

Everett WA

5602 B.D. Eindhoven

98206-9090

The Netherlands

Table of Contents

Title Introduction.................................................................................................................... Safety Information ......................................................................................................... Your Meter’s Features ................................................................................................... Power-Up Options .................................................................................................... Automatic Power-Off................................................................................................. Input Alert™ Feature ................................................................................................ Making Measurements .................................................................................................. Measuring AC and DC Voltage................................................................................. Testing for Continuity................................................................................................ Measuring Resistance .............................................................................................. Using Conductance for High Resistance or Leakage Tests ..................................... Measuring Capacitance ............................................................................................ Testing Diodes.......................................................................................................... Measuring AC or DC Current.................................................................................... Measuring Frequency............................................................................................... Measuring Duty Cycle............................................................................................... Determining Pulse Width ..........................................................................................

i

Page 1 1 4 11 11 12 12 12 14 16 18 18 21 22 25 27 28

80 Series III Users Manual Analog Bar Graph .......................................................................................................... Model 87 Bar Graph.................................................................................................. Models 83 and 85 Bar Graph .................................................................................... 4-1/2 Digit Mode (Model 87) .......................................................................................... MIN MAX Recording Mode ............................................................................................ ® Touch Hold Mode ....................................................................................................... Relative Mode ................................................................................................................ Zoom Mode (Models 83 and 85) ............................................................................... Uses for the Zoom Mode (Models 83 and 85)........................................................... Maintenance .................................................................................................................. General Maintenance................................................................................................ Testing the Fuses...................................................................................................... Replacing the Battery................................................................................................ Replacing the Fuses ................................................................................................. Service and Parts........................................................................................................... Specifications.................................................................................................................

ii

28 28 29 29 30 32 32 32 33 33 33 34 35 35 36 41

List of Tables Table 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19.

Title

Page

International Electrical Symbols ......................................................................................... Inputs ................................................................................................................................. Rotary Switch Positions ..................................................................................................... Pushbuttons ....................................................................................................................... Display Features ................................................................................................................ Estimating Capacitance Values Over 5 Microfarads .......................................................... Functions and Trigger Levels for Frequency Measurements ............................................. MIN MAX Functions ........................................................................................................... Replacement Parts............................................................................................................. Accessories........................................................................................................................ Models 85 and 87 AC Voltage Function Specifications...................................................... Model 83 AC Voltage Function Specifications ................................................................... DC Voltage, Resistance, and Conductance Function Specifications ................................. Current Function Specifications ......................................................................................... Capacitance and Diode Function Specifications................................................................ Frequency Counter Specifications ..................................................................................... Frequency Counter Sensitivity and Trigger Levels............................................................. Electrical Characteristics of the Terminals ......................................................................... MIN MAX Recording Specifications ...................................................................................

2 4 5 6 9 20 26 31 38 40 42 43 44 45 47 47 48 49 50

iii

80 Series III Users Manual

iv

List of Figures

Figure

Title

Page

1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11.

Display Features (Model 87 Shown).......................................................... Measuring AC and DC Voltage.................................................................. Testing for Continuity................................................................................. Measuring Resistance ............................................................................... Measuring Capacitance............................................................................. Testing a Diode ......................................................................................... Measuring Current..................................................................................... Components of Duty Cycle Measurements ............................................... Testing the Current Fuses ......................................................................... Battery and Fuse Replacement ................................................................. Replaceable Parts .....................................................................................

8 13 15 17 19 21 23 27 34 37 39

v

80 Series III Users Manual

vi

Introduction

Introduction WWarning Read "Safety Information" before you use the meter. Except where noted, the descriptions and instructions in this manual apply to Series III Models 83, 85, 87, and 87/E multimeters. Model 87 is shown in all illustrations.

In this manual, a Warning identifies conditions and actions that pose hazards to the user. A Caution identifies conditions and actions that may damage the meter or the equipment under test. International symbols used on the meter and in this manual are explained in Table 1.

WWarning

Safety Information

To avoid possible electric shock or personal injury, follow these guidelines:

This meter complies with:

•

Do not use the meter if it is damaged. Before you use the meter, inspect the case. Look for cracks or missing plastic. Pay particular attention to the insulation surrounding the connectors.

•

Make sure the battery door is closed and latched before you operate the meter.

•

Replace the battery as soon as the battery indicator (M) appears.

• • • • • •

EN61010.1:1993 ANSI/ISA S82.01-1994 CAN/CSA C22.2 No. 1010.1-92 1000 V Overvoltage Category III, Pollution Degree 2 600 V Overvoltage Category IV, Pollution Degree 2 UL3111-1

Use the meter only as specified in this manual, otherwise the protection provided by the meter may be impaired.

1

80 Series III Users Manual Table 1. International Electrical Symbols AC (Alternating Current)

Earth ground

DC (Direct Current)

Fuse

AC or DC

Conforms to European Union directives

Refer to the manual for information about this feature.

Conforms to relevant Canadian Standards Association directives

Battery

Double insulated

Inspected and licensed by TÜV Product Services.

2

Safety Information •

Remove test leads from the meter before you open the battery door.

•

Inspect the test leads for damaged insulation or exposed metal. Check the test leads for continuity. Replace damaged test leads before you use the meter.

Caution To avoid possible damage to the meter or to the equipment under test, follow these guidelines: •

Do not use the meter if it operates abnormally. Protection may be impaired. When in doubt, have the meter serviced.

Disconnect circuit power and discharge all high-voltage capacitors before testing resistance, continuity, diodes, or capacitance.

•

Use the proper terminals, function, and range for your measurements.

•

Do not operate the meter around explosive gas, vapor, or dust.

•

Before measuring current, check the meter’s fuses. (See "Testing the Fuses".)

•

Use only a single 9 V battery, properly installed in the meter case, to power the meter.

•

When servicing the meter, use only specified replacement parts.

•

3

80 Series III Users Manual To protect yourself, use the following guidelines: •

Use caution when working with voltages above 30 V ac rms, 42 V ac peak, or 60 V dc. Such voltages pose a shock hazard.

Table 2. Inputs Terminal

Description

Page

A

22

When using the probes, keep your fingers behind the finger guards.

Input for 0 A to 10.00 A current measurements

mA µA

22

Connect the common test lead before you connect the live test lead. When you disconnect test leads, disconnect the live test lead first.

Input for 0 µA to 400 mA current measurements

COM

Return terminal for all measurements

NA

•

Avoid working alone.

V eG

•

When measuring current, turn off circuit power before connecting the meter in the circuit. Remember to place the meter in series with the circuit.

Input for voltage, continuity, resistance, diode, capacitance, frequency, and duty cycle measurements

V: 12 e: 16 G: 21 E:18 Frequency: 25 Duty cycle: 27

• •

Your Meter’s Features Tables 2 through 5 briefly describe your meter’s features and give page numbers where you can find more detailed information about the features.

4

Your Meter’s Features Table 3. Rotary Switch Positions Switch Position

Function

Page

K

AC voltage measurement

12

L

DC voltage measurement

12

d mV

400 mV dc voltage range

12

R Continuity test

14

e Resistance measurement

16

E Capacitance measurement

18

Diode test

21

mA A

DC or AC current measurements from 0 mA to 10.00 A

22

µA

DC or AC current measurements from 0 µA to 4000 µA

22

ReE

G

5

80 Series III Users Manual Table 4. Pushbuttons Button

Function

U ReE (Blue button)

Page

Selects capacitance.

18

mA/A, µA

Switches between dc and ac current.

22

Power-up

Disables automatic power-off feature.

11

Starts recording of minimum and maximum values. Steps the display through MIN, MAX, AVG (average), and present readings.

30

position

Power-up

Enables high-accuracy 1-second response time for MIN MAX recording.

30

M Any switch

K Any switch position

Power-up

Switches between the ranges available for the selected function. To return to autoranging, hold the button down for 1 second. Manually selecting a range causes the meter to exit the Touch Hold®, MIN MAX, and REL (relative) modes.

See ranges in specifications.

For servicing purposes only.

NA

Touch Hold captures the present reading on the display. When a new, stable reading is detected, the meter beeps and displays the new reading.

32

MIN MAX recording

Stops and starts recording without erasing recorded values.

30

Frequency counter

Stops and starts the frequency counter.

25

I Any switch position

6

Button Function

Your Meter’s Features Table 4. Pushbuttons (cont) Button

b Model 87: yellow button

Function

Page

Any switch position

Turns the backlight on and off.

NA

For Model 87, hold the yellow button down for one second to enter the 4-1/2 digit mode. To return to the 3-1/2 digit mode, hold the button down only until all display segments turn on (about one second).

29

Continuity ReE

Turns the continuity beeper on and off.

14

MIN MAX recording

On Model 87, switches between 250 µs and 100 ms or 1 s response times.

30

b Models 83, 85: gray button T

Button Function

Power-up

NA Disables the beeper for all functions.

C (Relative mode)

F

Any switch position

Stores the present reading as a reference for subsequent readings. The display is zeroed, and the stored reading is subtracted from all subsequent readings.

32

Power-up

For Models 83 and 85, enables zoom mode for the bar graph.

32

Any switch position

Starts the frequency counter.

25

Press again to enter duty cycle mode.

27

Provides >4000 MΩ input impedance for the 400 mV dc range.

NA

Power-up

7

80 Series III Users Manual

6

8

7

9

5 4 10 10 3 2

1011

1 12

13

iy1f.eps

Figure 1. Display Features (Model 87 Shown)

8

Your Meter’s Features Table 5. Display Features Number

Feature

A

±

B C D

Page

Polarity indicator for the analog bar graph.

28

Q

Relative (REL) mode is active.

32

S

The continuity beeper is on.

14

Indicates negative readings. In relative mode, this sign indicates that the present input is less than the stored reference.

32

-

E

The battery is low. WWarning: To avoid false readings, which could lead to possible electric shock or personal injury, replace the battery as soon as the battery indicator appears.

F

AUTO

G

100 ms MAX MIN AVG

H I

Indication

AC DC

35

The meter is in autorange mode and automatically selects the range with the best resolution.

NA

Indicators for minimum-maximum recording mode.

30

Touch Hold is active.

32

Indicator for ac or dc voltage or current. AC voltage and current is displayed as an rms (root mean square) value.

12, 22

9

80 Series III Users Manual Table 5. Display Features (continued) Number

Feature

J

A, µA, mA V, mV µF, nF nS % e, Me, ke Hz, kHz, MHz

10

Indication

Page

A: Amperes (amps). The unit of current. µA: Microamp. 1 x 10-6 or 0.000001 amperes. mA: Milliamp. 1 x 10-3 or 0.001 amperes.

22

V: Volts. The unit of voltage. mV: Millivolt. 1 x 10-3 or 0.001 volts.

12

F: Farad. The unit of capacitance. µF: Microfarad. 1 x 10-6 or 0.000001 farads. nF: Nanofarad. 1 x 10-9 or 0.000000001 farads.

18

S: Siemen. The unit of conductance. nS: Nanosiemen. 1 x 10-9 or 0.000000001 siemens.

18

Percent. Used for duty cycle measurements.

27

Ω: Ohm. The unit of resistance. MΩ: Megohm. 1 x 106 or 1,000,000 ohms. kΩ: Kilohm. 1 x 103 or 1000 ohms.

16

Hz: Hertz. The unit of frequency. kHz: Kilohertz. 1 x 103 or 1000 hertz. MHz: Megahertz. 1 x 106 or 1,000,000 hertz.

25

Your Meter’s Features Table 5. Display Features (continued) Number

Feature

K

4000 mV

L

Analog bar graph

M

0L

Indication Displays the currently selected range.

Provides an analog indication of the present inputs. The input (or the relative value when in relative mode) is too large for the selected range. For duty cycle measurements OL is displayed when the input signal stays high or low.

Page See specifications for ranges for each function. 28 Duty cycle: 27

Power-Up Options

Automatic Power-Off

Holding a button down while turning the meter on activates a power-up option. Table 4 includes the powerup options available. These options are also listed on the back of the meter.

The meter automatically turns off if you do not turn the rotary switch or press a button for 30 minutes. To disable automatic power-off, hold down the blue button while turning the meter on. Automatic power-off is always disabled in MIN MAX recording mode.

11

80 Series III Users Manual

Input Alert™ Feature

Measuring AC and DC Voltage

If a test lead is plugged into the mA/µA or A terminal, but the rotary switch is not correctly set to the mA/µA or A position, the beeper warns you by making a chirping sound. This warning is intended to stop you from attempting to measure voltage, continuity, resistance, capacitance, or diode values when the leads are plugged into a current terminal. Placing the probes across (in parallel with) a powered circuit when a lead is plugged into a current terminal can damage the circuit you are testing and blow the meter’s fuse. This can happen because the resistance through the meter’s current terminals is very low, so the meter acts like a short circuit.

Voltage is the difference in electrical potential between two points. The polarity of ac (alternating current) voltage varies over time, while the polarity of dc (direct current) voltage is constant over time. The meter presents ac voltage values as rms (root mean square) readings. The rms value is the equivalent dc voltage that would produce the same amount of heat in a resistance as the measured sinewave voltage. Models 85 and 87 feature true rms readings, which are accurate for other wave forms (with no dc offset) such as square waves, triangle waves, and staircase waves.

Making Measurements The following sections describe how to take measurements with your meter.

12

The meter’s voltage ranges are 400 mV, 4 V, 40 V, 400 V, and 1000 V. To select the 400 mV dc range, turn the rotary switch to mV. To measure ac or dc voltage, set up and connect the meter as shown in Figure 2.

Making Measurements The following are some tips for measuring voltage: •

•

AC Voltage

When you measure voltage, the meter acts approximately like a 10 MΩ (10,000,000 Ω) impedance in parallel with the circuit. This loading effect can cause measurement errors in highimpedance circuits. In most cases, the error is negligible (0.1% or less) if the circuit impedance is 10 kΩ (10,000 Ω) or less.

87 III TRUE RMS MULTIMETER

MIN MAX

RANGE

HOLD

REL 41/2 DIGITS 1 Second

Switch Box

H

Hz

PEAK MIN MAX

mV mA A

V

V

µA

V

OFF

mA µA COM V

A

For better accuracy when measuring the dc offset of an ac voltage, measure the ac voltage first. Note the ac voltage range, then manually select a dc voltage range equal to or higher than the ac range. This procedure improves the accuracy of the dc measurement by ensuring that the input protection circuits are not activated.

!

400mA MAX FUSED

10A MAX FUSED

CAT II

1000V MAX

!

DC Voltage 87 III TRUE RMS MULTIMETER

MIN MAX

RANGE

HOLD

REL 41/2 DIGITS 1 Second

H

Hz

PEAK MIN MAX

mV

V

mA A

V

µA

V

OFF

A

mA µA COM V !

10A MAX FUSED

400mA MAX FUSED

CAT II

+

1000V MAX

!

iy2f.eps

Figure 2. Measuring AC and DC Voltage

13

80 Series III Users Manual

Testing for Continuity Caution To avoid possible damage to the meter or to the equipment under test, disconnect circuit power and discharge all high-voltage capacitors before testing for continuity. Continuity is the presence of a complete path for current flow. The continuity test features a beeper that sounds if a circuit is complete. The beeper allows you to perform quick continuity tests without having to watch the display. To test for continuity, set up the meter as shown in Figure 3. Press Tto turn the continuity beeper on or off.

14

The continuity function detects intermittent opens and shorts lasting as little as 1 millisecond (0.001 second). These brief contacts cause the meter to emit a short beep.

Making Measurements

For in-circuit tests, turn circuit power off.

87 III TRUE RMS MULTIMETER

MIN MAX

RANGE

HOLD

REL

4 1/2 DIGITS 1 Seconds

Activates continuity beeper

87 III TRUE RMS MULTIMETER

MIN MAX

H

RANGE

4 1/2 DIGITS 1 Seconds

H

Hz

PEAK MIN MAX

mV

mV mA A

V

mA A

V

µA

V

µA

V

OFF

OFF

A

mA µA COM V !

!

10A MAX FUSED

HOLD

REL

Hz

PEAK MIN MAX

400mA MAX FUSED

CAT II

10A MAX FUSED

1000V MAX

!

400mA MAX FUSED

CAT II

1000V MAX

!

ON (closed)

OFF (open)

iy4f.eps

Figure 3. Testing for Continuity

15

80 Series III Users Manual

Measuring Resistance Caution To avoid possible damage to the meter or to the equipment under test, disconnect circuit power and discharge all high-voltage capacitors before measuring resistance. Resistance is an opposition to current flow. The unit of resistance is the ohm (Ω). The meter measures resistance by sending a small current through the circuit. Because this current flows through all possible paths between the probes, the resistance reading represents the total resistance of all paths between the probes. The meter’s resistance ranges are 400 Ω, 4 kΩ, 40 kΩ, 400 kΩ, 4 MΩ, and 40 MΩ. To measure resistance, set up the meter as shown in Figure 4.

16

The following are some tips for measuring resistance: •

Because the meter’s test current flows through all possible paths between the probe tips, the measured value of a resistor in a circuit is often different from the resistor’s rated value.

•

The test leads can add 0.1 Ω to 0.2 Ω of error to resistance measurements. To test the leads, touch the probe tips together and read the resistance of the leads. If necessary, you can use the relative (REL) mode to automatically subtract this value.

•

The resistance function can produce enough voltage to forward-bias silicon diode or transistor junctions, causing them to conduct. To avoid this, do not use the 40 MΩ range for in-circuit resistance measurements.

Making Measurements

In-Circuit Resistance Measurements

Isolating a Potentiometer

Circuit Power

OFF

1

3 2 Disconnect 2

1 87 III TRUE RMS MULTIMETER

3 MIN MAX

RANGE

HOLD

REL 4 1/2 DIGITS 1 Seconds

Isolating a Resistor

H

Hz

PEAK MIN MAX

mV mA A

V

µA

V

OFF

A

mA µA

V

COM

!

10A MAX FUSED

400mA MAX FUSED

CAT II

1000V MAX

!

Disconnect iy6f.eps

Figure 4. Measuring Resistance

17

80 Series III Users Manual

Using Conductance for High Resistance or Leakage Tests

The following are some tips for measuring conductance: •

High-resistance readings are susceptible to electrical noise. To smooth out most noisy readings, enter the MIN MAX recording mode; then scroll to the average (AVG) reading.

•

There is normally a residual conductance reading with the test leads open. To ensure accurate readings, use the relative (REL) mode to subtract the residual value.

Conductance, the inverse of resistance, is the ability of a circuit to pass current. High values of conductance correspond to low values of resistance. The unit of conductance is the Siemen (S). The meter’s 40 nS range measures conductance in nanosiemens (1 nS = 0.000000001 Siemens). Because such small amounts of conductance correspond to extremely high resistance, the nS range lets you determine the resistance of components up to 100,000 MΩ, or 100,000,000,000 Ω (1/1 nS = 1,000 MΩ). To measure conductance, set up the meter as shown for measuring resistance (Figure 4); then press Kuntil the nS indicator appears on the display.

Measuring Capacitance Caution To avoid possible damage to the meter or to the equipment under test, disconnect circuit power and discharge all high-voltage capacitors before measuring capacitance. Use the dc voltage function to confirm that the capacitor is discharged. Capacitance is the ability of a component to store an electrical charge. The unit of capacitance is the farad (F). Most capacitors are in the nanofarad to microfarad range.

18

Making Measurements The meter measures capacitance by charging the capacitor with a known current for a known period of time, measuring the resulting voltage, then calculating the capacitance. The measurement takes about 1 second per range. The capacitor charge can be up to 1.2 V.

87 III TRUE RMS MULTIMETER

µ nF MIN MAX

RANGE

HOLD

REL

Select Capacitance

H

Hz

4 1/2 DIGITS PEAK MIN MAX 1 Seconds

The meter’s capacitance ranges are 5 nF, 0.05 µF, 0.5 µF, and 5 µF.

mV

µA

OFF

A

To measure capacitance, set up the meter as shown in Figure 5.

mA A

V

V

mA µA

V

COM

!

10A MAX FUSED

400mA MAX FUSED

CAT II

1000V MAX

!

The following are some tips for measuring capacitance: •

To speed up measurements of similar values, press Kto manually select the proper range.

•

To improve the accuracy of measurements less than 5 nF, use the relative (REL) mode to subtract the residual capacitance of the meter and leads.

+ + + + + + + +

+ iy10f.eps

Figure 5. Measuring Capacitance

19

80 Series III Users Manual •

To estimate capacitance values above 5 µF, use the current supplied by the meter’s resistance function, as follows: 1.

Set up the meter to measure resistance.

2.

Press Kto select a range based on the value of capacitance you expect to measure (refer to Table 6.)

3.

Discharge the capacitor.

4.

Place the meter’s leads across the capacitor; then time how long it takes for the display to reach OL.

5.

20

Multiply the charge time from step 4 by the appropriate value in the µF/second of Charge Time column in 6. The result is the estimated capacitance value in microfarads (µF).

Table 6. Estimating Capacitance Values Over 5 Microfarads

Expected Capacitance

Suggested Range*

µF/second of Charge Time

Up to 10 µF

4 Me

0.3

11 µF to 100 µF

400 ke

3

101 µF to 1000 µF

40 ke

30

1001 µF to 10,000 µF

4 ke

300

10,000 µF to 100,000 µF

400 e

3000

*These ranges keep the full-charge time between 3.7 seconds and 33.3 seconds for the expected capacitance values. If the capacitor charges too quickly for you to time, select the next higher resistance range.

Making Measurements

Testing Diodes Forward Bias

Caution To avoid possible damage to the meter or to the equipment under test, disconnect circuit power and discharge all high-voltage capacitors before testing diodes.

87 III TRUE RMS MULTIMETER

MIN MAX

RANGE

HOLD

REL 4 1/2 DIGITS

Typical Reading

+

H

Hz

PEAK MIN MAX

1 Seconds

mV mA A

V

µA

V

OFF

Use the diode test to check diodes, transistors, silicon controlled rectifiers (SCRs), and other semiconductor devices. This function tests a semiconductor junction by sending a current through the junction, then measuring the junction’s voltage drop. A good silicon junction drops between 0.5 V and 0.8 V. To test a diode out of a circuit, set up the meter as shown in Figure 6. For forward-bias readings on any semiconductor component, place the red test lead on the component’s positive terminal and place the black lead on the component’s negative terminal.

mA µA

A

V

COM

!

400mA MAX FUSED

10A MAX FUSED

CAT II

1000V MAX

!

Reverse Bias 87 III TRUE RMS MULTIMETER

+ MIN MAX

RANGE

HOLD

REL 4 1/2 DIGITS

H

Hz

PEAK MIN MAX

1 Seconds

mV mA A

V

µA

V

OFF

In a circuit, a good diode should still produce a forwardbias reading of 0.5 V to 0.8 V; however, the reverse-bias reading can vary depending on the resistance of other pathways between the probe tips.

A

mA µA

V

COM

!

10A MAX FUSED

400mA MAX FUSED

CAT II

1000V MAX

!

iy9f.eps

Figure 6. Testing a Diode

21

80 Series III Users Manual

Measuring AC or DC Current

WWarning Never attempt an in-circuit current measurement where the open-circuit potential to earth is greater than 1000 V. You may damage the meter or be injured if the fuse blows during such a measurement. Caution To avoid possible damage to the meter or to the equipment under test, check the meter’s fuses before measuring current. Use the proper terminals, function, and range for your measurement. Never place the probes across (in parallel with) any circuit or component when the leads are plugged into the current terminals. Current is the flow of electrons through a conductor. To measure current, you must break the circuit under test, then place the meter in series with the circuit.

22

The meter’s current ranges are 400 µA, 4000 µA, 40 mA, 400 mA, 4000 mA, and 10 A. AC current is displayed as an rms value. To measure current, refer to Figure 7 and proceed as follows: 1.

Turn off power to the circuit. Discharge all highvoltage capacitors.

2.

Insert the black lead into the COM terminal. For currents between 4 mA and 400 mA, insert the red lead into the mA/µA terminal. For currents above 400 mA, insert the red lead into the A terminal.

Note To avoid blowing the meter’s 400 mA fuse, use the mA/µA terminal only if you are sure the current is less than 400 mA.

Making Measurements

1

Circuit Power: OFF to connect meter. ON for measurement. OFF to disconnect meter.

Total current to circuit

4 87 III TRUE RMS MULTIMETER

5

AC DC

MIN MAX

RANGE

HOLD

REL 4 1/2 DIGITS 1 Seconds

Hz

PEAK MIN MAX

mV

mA A µA

Current through one component

mA A

V

µA

V

2

OFF

A

3

H

mA µA COM V !

10A MAX FUSED

400mA MAX FUSED

CAT II

1000V MAX

!

5 iy7f.eps

Figure 7. Measuring Current

23

80 Series III Users Manual 3.

If you are using the A terminal, set the rotary switch to mA/A. If you are using the mA/µA terminal, set the rotary switch to µA for currents below 4000 µA (4 mA), or mA/A for currents above 4000 µA.

4.

To measure ac current, press the blue button.

5.

Break the circuit path to be tested. Touch the black probe to the more negative side of the break; touch the red probe to the more positive side of the break. Reversing the leads will produce a negative reading, but will not damage the meter.

6.

Turn on power to the circuit; then read the display. Be sure to note the unit given at the right side of the display (µA, mA, or A).

7.

Turn off power to the circuit and discharge all highvoltage capacitors. Remove the meter and restore the circuit to normal operation.

24

The following are some tips for measuring current: •

If the current reading is 0 and you are sure the meter is set up correctly, test the meter’s fuses as described under "Testing the Fuses".

•

A current meter drops a small voltage across itself, which might affect circuit operation. You can calculate this burden voltage using the values listed in the specifications in Table 14.

Making Measurements

Measuring Frequency

The following are some tips for measuring frequency:

Frequency is the number of cycles a signal completes each second. The meter measures the frequency of a voltage or current signal by counting the number of times the signal crosses a threshold level each second.

•

If a reading shows as 0 Hz or is unstable, the input signal may be below or near the trigger level. You can usually correct these problems by selecting a lower range, which increases the sensitivity of the meter. In the L function, the lower ranges also have lower trigger levels.

•

If a reading seems to be a multiple of what you expect, the input signal may be distorted. Distortion can cause multiple triggerings of the frequency counter. Selecting a higher voltage range might solve this problem by decreasing the sensitivity of the meter. You can also try selecting a dc range, which raises the trigger level. In general, the lowest frequency displayed is the correct one.

Table 7 summarizes the trigger levels and applications for measuring frequency using the various ranges of the meter’s voltage and current functions. To measure frequency, connect the meter to the signal source; then press F. Pressing Tswitches the trigger slope between + and -, as indicated by the symbol at the left side of the display (refer to Figure 8 under "Measuring Duty Cycle"). Pressing Istops and starts the counter. The meter autoranges to one of five frequency ranges: 199.99 Hz, 1999.9 Hz, 19.999 kHz, 199.99 kHz, and greater than 200 kHz. For frequencies below 10 Hz, the display is updated at the frequency of the input. Between 0.5 Hz and 0.3 Hz, the display may be unstable. Below 0.3 Hz, the display shows 0.000 Hz.

25

80 Series III Users Manual Table 7. Functions and Trigger Levels for Frequency Measurements

Function

K

Approximate Trigger Level

Typical Application

4 V, 40 V, 400 V, 1000 V

0V

Most signals.

400 mV

0V

High-frequency 5 V logic signals. (The dc-coupling of the L function can attenuate high-frequency logic signals, reducing their amplitude enough to interfere with triggering.)

L

400 mV

40 mV

Refer to the measurement tips given before this table.

L

4V

1.7 V

5 V logic signals (TTL).

L

40 V

4V

Automotive switching signals.

L

400 V

40 V

Refer to the measurement tips given before this table.

L

1000 V

400 V

K

ReEG \

Frequency counter characteristics are not specified for these functions. 0A

AC current signals.

µAF

400 µA

Refer to the measurement tips given before this table.

^

40 mA

AF

26

Range

All ranges

4A

Making Measurements frequency function, you can change the slope for the meter’s counter by pressing T.

Measuring Duty Cycle Duty cycle (or duty factor) is the percentage of time a signal is above or below a trigger level during one cycle (Figure 8). The duty cycle mode is optimized for measuring the on or off time of logic and switching signals. Systems such as electronic fuel injection systems and switching power supplies are controlled by pulses of varying width, which can be checked by measuring duty cycle.

For 5 V logic signals, use the 4 V dc range. For 12 V switching signals in automobiles, use the 40 V dc range. For sine waves, use the lowest range that does not result in multiple triggering. (Normally, a distortion-free signal can be up to ten times the amplitude of the selected voltage range.) If a duty cycle reading is unstable, press MIN MAX; then scroll to the AVG (average) display.

To measure duty cycle, set up the meter to measure frequency; then press Hz a second time. As with the

+Slope Trigger Point

-Slope Trigger Point 30% Above +Slope

70% Below -Slope 100% iy3f.eps

Figure 8. Components of Duty Cycle Measurements

27

80 Series III Users Manual

Determining Pulse Width

Analog Bar Graph

For a periodic waveform (its pattern repeats at equal time intervals), you can determine the amount of time that the signal is high or low as follows:

The analog bar graph functions like the needle on an analog meter, but without the overshoot. The bar graph is updated 40 times per second. Because the graph responds 10 times faster than the digital display, it is useful for making peak and null adjustments and observing rapidly changing inputs.

1.

Measure the signal’s frequency.

2.

Press Fa second time to measure the signal’s duty cycle. Press T to select a measurement of the signal’s positive or negative pulse. (Refer to Figure 8.)

3.

Use the following formula to determine the pulse width: Pulse Width = % Duty Cycle ÷ 100 (in seconds) Frequency

28

Model 87 Bar Graph Model 87’s bar graph consists of 32 segments. The position of the pointer on the display represents the last three digits of the digital display. For example, for inputs of 500 Ω, 1500 Ω, and 2500 Ω, the pointer is near 0.5 on the scale. If the last three digits are 999, the pointer is at the far right of the scale. As the digits increment past 000, the pointer wraps back to the left side of the display. The polarity indicator at the left of the graph indicates the polarity of the input.

4-1/2 Digit Mode (Model 87)

Models 83 and 85 Bar Graph

4-1/2 Digit Mode (Model 87)

The bar graph on Models 83 and 85 consists of 43 segments. The number of lit segments is relative to the full-scale value of the selected range. The polarity indicator at the left of the graph indicates the polarity of the input. For example, if the 40 V range is selected, the "4" on the scale represents 40 V. An input of -30 V would light the negative sign and the segments up to the "3" on the scale.

On a Model 87 meter, pressing the yellow button for one second causes the meter to enter the high-resolution, 4-1/2 digit mode. Readings are displayed at 10 times the normal resolution with a maximum display of 19,999 counts. The display is updated once per second. The 4-1/2 digit mode works in all modes except capacitance and the 250 µs and 100 ms MIN MAX modes.

If the input equals or exceeds the 4096 counts on a manually-selected range, all segments are lit and® appears to the right of the bar graph. The graph does not operate with the capacitance or frequency counter functions.

To return to the 3-1/2 digit mode, press the yellow button only until all of the display segments turn on (about one second).

The bar graph on Models 83 and 85 also has a zoom function, as described under "Zoom Mode".

29

80 Series III Users Manual

MIN MAX Recording Mode The MIN MAX mode records minimum and maximum input values. When the inputs go below the recorded minimum value or above the recorded maximum value, the meter beeps and records the new value. This mode can be used to capture intermittent readings, record maximum readings while you are away, or record readings while you are operating the equipment under test and cannot watch the meter. MIN MAX mode can also calculate an average of all readings taken since the MIN MAX mode was activated. To use MIN MAX mode, refer to the functions in Table 8. Response time is the length of time an input must stay at a new value to be recorded. A shorter response time captures shorter events, but with decreased accuracy. Changing the response time erases all recorded readings. Models 83 and 85 have 100 millisecond and 1 second response times; Model 87 has 1 second, 100 millisecond, and 250 µs (peak) response times. The 250 µs response time is indicated by "1 ms" on the display.

30

The 100 millisecond response time is best for recording power supply surges, inrush currents, and finding intermittent failures. This response time follows the update time of the analog display. The high-accuracy 1 second response time has the full accuracy of the meter and is best for recording power supply drift, line voltage changes, or circuit performance while line voltage, temperature, load, or some other parameter is being changed. The true average value (AVG) displayed in the 100 ms and 1 s modes is the mathematical integral of all readings taken since you started recording. The average reading is useful for smoothing out unstable inputs, calculating power consumption, or estimating the percent of time a circuit is active.

MIN MAX Recording Mode Table 8. MIN MAX Functions Button

MIN MAX Function

M

Enter MIN MAX recording mode. The meter is locked in the range displayed before you entered MIN MAX mode. (Select the desired measurement function and range before entering MIN MAX.) The meter beeps each time a new minimum or maximum value is recorded.

M

Scroll through minimum (MIN), maximum (MAX), and average (AVG) values.

(While in MIN MAX mode)

T PEAK MIN MAX

Model 87 only: Select 100 ms or 250 µs response time. (The 250 µs response time is indicated by "1 ms" on the display.) Stored values are erased. The present and AVG (average) values are not available when 250 µs is selected.

I

Stop recording without erasing stored values. Press again to resume recording.

M

Exit MIN MAX mode. Stored values are erased. The meter stays in the selected range.

(hold for 1 second) Hold down M while turning the meter on

Select 1 s high-accuracy response time. See text under "MIN MAX Recording Mode" for more explanation. MIN MAX readings for the frequency counter are recorded only in the high-accuracy mode.

31

80 Series III Users Manual

Touch Hold ® Mode WWarning The Touch Hold mode will not capture unstable or noisy readings. Do not use Touch Hold mode to determine that circuits are without power. The Touch Hold mode captures the present reading on the display. When a new, stable reading is detected, the meter beeps and displays the new reading. To enter or exit Touch Hold mode, press I.

Relative Mode Selecting relative mode ( C) causes the meter to zero the display and store the present reading as the reference for subsequent measurements. The meter is locked into the range selected when you pressed C. Press Cagain to exit this mode.

32

In relative mode, the reading shown is always the difference between the present reading and the stored reference value. For example, if the stored reference value is 15.00 V and the present reading is 14.10 V, the display shows -0.90 V. On Model 87, the relative mode does not change the operation of the analog display.

Zoom Mode (Models 83 and 85) Selecting relative mode on a Model 83 or 85 meter causes the bar graph to enter Zoom mode. In zoom mode, the center of the graph represents zero and the sensitivity of the bar graph increases by a factor of 10. Measured values more negative than the stored reference light segments to the left of center; values more positive light segments to the right of center.

Maintenance

Uses for the Zoom Mode (Models 83 and 85)

Maintenance

The relative mode, combined with the increased sensitivity of the bar graph’s zoom mode, helps you make fast and accurate zero and peak adjustments.

Repairs or servicing not covered in this manual should be performed only by qualified personnel as described in the 80 Series III Service Manual.

For zero adjustments, set the meter to the desired function, short the test leads together, press C; then connect the leads to the circuit under test. Adjust the circuit’s variable component until the display reads zero. Only the center segment on the Zoom bar graph is lit.

General Maintenance

For peak adjustments, set the meter to the desired function, connect the leads to the circuit under test; then press C. The display reads zero. As you adjust for a positive or negative peak, the bar graph length increases to the right or left of zero. If an overange symbol lights (Û ® ), press C twice to set a new reference; then continue with your adjustment.

Periodically wipe the case with a damp cloth and mild detergent. Do not use abrasives or solvents. Dirt or moisture in the terminals can affect readings and can falsely activate the Input Alert feature. Clean the terminals as follows: 1.

Turn the meter off and remove all test leads.

2.

Shake out any dirt that may be in the terminals.

3.

Soak a new swab with a cleaning and oiling agent (such as WD-40). Work the swab around in each terminal. The oiling agent insulates the terminals from moisture-related activation of the Input Alert feature.

33

80 Series III Users Manual

Testing the Fuses Before measuring current, test the appropriate fuse as shown in Figure 9. If the tests give readings other than those shown, have the meter serviced.

Good F2 fuse: 00.0 Ω to 00.5 Ω Replace fuse: OL

87

TRUE RMS MULTIMETER

MIN MAX

RANGE

HOLD

REL

mA A

V

µA

V

WWarning To avoid electrical shock or personal injury, remove the test leads and any input signals before replacing the battery or fuses. To prevent damage or injury, install ONLY specified replacement fuses with the amperage, voltage, and speed ratings shown in Table 9.

H

Hz

PEAK MIN MAX

mV

OFF

Touch top half of input contacts

mA µA

A

V

COM

!

400mA MAX FUSED

10A MAX FUSED

!

87

!

CAT II CA 10 T II 1000V MAX 00 V M AX

TRUE RMS MULTIMETER

MIN MAX

RANGE

HOLD

REL

H

Hz

PEAK MIN MAX

Good F1 fuse: 0.995 kΩ to 1.005 kΩ Replace fuse: OL

mV mA A

V

µA

V

OFF

A

mA µA

V

COM

!

10A MAX FUSED

400mA MAX FUSED !

!

CAT II CA 10 T II 1000V MAX 00 V M AX

iy5f.eps

Figure 9. Testing the Current Fuses

34

Maintenance

Replacing the Battery

Replacing the Fuses

Replace the battery with a 9 V battery (NEDA A1604, 6F22, or 006P).

Referring to Figure 10, examine or replace the meter’s fuses as follows:

WWarning To avoid false readings, which could lead to possible electric shock or personal injury, replace the battery as soon as the battery indicator (B) appears. Replace the battery as follows (refer to Figure 10): 1. 2.

3.

Turn the rotary switch to OFF and remove the test leads from the terminals. Remove the battery door by using a standard-blade screwdriver to turn the battery door screws onequarter turn counterclockwise. Replace the battery and the battery door. Secure the door by turning the screws one-quarter turn clockwise.

1.

Turn the rotary switch to OFF and remove the test leads from the terminals.

2.

Remove the battery door by using a standard-blade screwdriver to turn the battery door screws onequarter turn counterclockwise.

3.

Remove the three Phillips-head screws from the case bottom and turn the case over.

4.

Gently lift the input terminal-end of the top case to separate the two halves of the case.

5.

Remove the fuse by gently prying one end loose, then sliding the fuse out of its bracket.

6.

Install ONLY specified replacement fuses with the amperage, voltage, and speed ratings shown in Table 9.

35

80 Series III Users Manual 6.

Verify that the rotary switch and the circuit board switch are in the OFF position.

7.

Replace the case top, ensuring that the gasket is properly seated and case snaps together above the LCD (item A).

8.

Reinstall the three screws and the battery door. Secure the door by turning the screws one-quarter turn clockwise.

Service and Parts If the meter fails, check the battery and fuses. Review this manual to verify proper use of the meter. Replacement parts and accessories are shown in Tables 9 and 10 and Figure 11. To contact Fluke, call one of the following telephone numbers: USA: 1-888-99-FLUKE (1-888-993-5853) Canada: 1-800-36-FLUKE (1-800-363-5853) Europe: +31 402-678-200 Japan: +81-3-3434-0181 Singapore: +65-738-5655 Anywhere in the world: +1-425-356-5500 Or, visit Fluke’s Web site at www.fluke.com.

36

Service and Parts

F1 F2

1

iy12f.eps

Figure 10. Battery and Fuse Replacement

37

80 Series III Users Manual Table 9. Replacement Parts

Item

Description

BT1 Battery, 9 V F1 W Fuse, 0.440 A, 1000 V, FAST F2 W Fuse, 11 A, 1000 V, FAST H1 Screw, Case MP1 Foot, Non-Skid MP2 O-Ring, Input Receptacle TM1 CD-ROM (contains Users Manual) TM2 Getting Started Manual TM3 Quick Reference Guide, Fluke 80 Series III TM4 Service Manual WTo ensure safety, use exact replacement only.

38

Fluke Part or Model Number

Quantity

614487 943121 803293 832246 824466 831933 1611720 1611712 688168 688645

1 1 1 3 2 1 1 1 1 Optional

Service and Parts

TL75 Test Lead Set

MP85 T24 Test Lead Set

S1 TP1, TP4 Probes

AC20 Alligator Clip (Black)

87/E Test Lead Set

F2

AC70A Alligator Clips

F1 MP2 TM1

C81Y

MP86 TM2

H1 BT1

MP1 MP92 TM3

H5, 6 iy11f.eps

Figure 11. Replaceable Parts

39

80 Series III Users Manual Table 10. Accessories*

Item TL20 AC70A TL75 TL24 TP1 TP4 AC20 C81Y C81G C25

Description Industrial Test Lead Set (Optional) Alligator Clips for use with TL75 test lead set Test Lead Set Test Lead Set, Heat-Resistant Silicone Test Probes, Flat Blade, Slim Reach Test Probes, 4 mm diameter, Slim Reach Safety Grip, Wide-Jaw Alligator Clips Holster, Yellow Holster, Gray (Optional) Carrying Case, Soft (Optional)

* Fluke accessories are available from your authorized Fluke distributor.

40

Fluke Part Number TL20 AC70A TL75 TL24 TP1 TP4 AC20 C81Y C81G C25

Quantity  1 1     1  

Specifications

Specifications Maximum Voltage between any Terminal and Earth Ground: 1000 V rms

WFuse Protection for mA or µA inputs: 44/100 A, 1000 V FAST Fuse WFuse Protection for A input: 11 A, 1000 V FAST Fuse Display: Digital: 4000 counts updates 4/sec; (Model 87 also has 19,999 counts in 4½-digit mode, updates 1/sec.). Analog: updates 40/sec. Frequency: 19,999 counts, updates 3/sec at >10 Hz. Model 87: 4 x 32 segments (equivalent to 128); Models 83, 85: 43 segments. Temperature: Operating: -20°C to +55°C; Storage: -40°C to +60°C Altitude: Operating: 2000 m; Storage: 10,000 m Temperature Coefficient: 0.05 x (specified accuracy)/ °C (28°C) Electromagnetic Compatibility: In an RF field of 3 V/m total accuracy = specified accuracy except: Models 85,87: Total Accuracy = Specified Accuracy + 0.4% of range above 800 MHz (µADC only). (mVAC and µAAC unspecified). Model 83: Total Accuracy = Specified Accuracy + 5% of range above 300 MHz (µADC only). (VDC unspecified). Relative Humidity: 0% to 90% (0°C to 35°C); 0% to 70% (35°C to 55°C) Battery Type: 9 V zinc, NEDA 1604 or 6F22 or 006P Battery Life: 400 hrs typical with alkaline (with backlight off) Shock Vibration: Per MIL-T-28800 for a Class 2 instrument Size (HxWxL): 1.25 in x 3.41 in x 7.35 in (3.1 cm x 8.6 cm x 18.6 cm) Size with Holster and Flex-Stand: 2.06 in x 3.86 in x 7.93 in (5.2 cm x 9.8 cm x 20.1 cm) Weight: 12.5 oz (355 g) Weight with Holster and Flex-Stand: 22.0 oz (624 g) Safety: Complies with ANSI/ISA S82.01-1994, CSA 22.2 No. 1010.1:1992 to 1000 V Overvoltage Category III, IEC 664 to 600 V Overvoltage Category IV. UL listed to UL3111-1. Licensed by TÜV to EN61010-1.

41

80 Series III Users Manual Table 11. Models 85 and 87 AC Voltage Function Specifications Function

K3

Range

400.0 mV 4.000 V 40.00 V 400.0 V 1000 V

Accuracy1

Resolution

0.1 mV 0.001 V 0.01 V 0.1 V 1V

50 Hz - 60 Hz ±(0.7% + 4) ±(0.7% + 2) ±(0.7% + 2) ±(0.7% + 2) ±(0.7% + 2)

45 Hz - 1 kHz ±(1.0% + 4) ±(1.0% + 4) ±(1.0% + 4) ±(1.0% + 4) ±(1.0% + 4)5

1 kHz - 5 kHz ±(2.0% + 4) ±(2.0% + 4) ±(2.0% + 4) ±(2.0% + 4)4 unspecified

5 kHz - 20 kHz2 ±(2.0% + 20) ±(2.0% + 20) ±(2.0% + 20) unspecified unspecified

1.

Accuracy is given as ±([% of reading] + [number of least significant digits]) at 18°C to 28°C, with relative humidity up to 90%, for a period of one year after calibration. For Model 87 in the 4 ½-digit mode, multiply the number of least significant digits (counts) by 10. AC conversions are ac-coupled and valid from 5% to 100% of range. Models 85 and 87 are true rms responding. AC crest factor can be up to 3 at full scale, 6 at half scale. For non-sinusoidal wave forms add -(2% Rdg + 2% full scale) typical, for a crest factor up to 3.

2.

Below 10% of range, add 6 counts.

3.

Models 85 and 87 are true rms responding meters. When the input leads are shorted together in the ac functions, the meters display a reading (typically 10 A: unspecified.

6.

Below a reading of 200 counts, add 10 counts.

45

80 Series III Users Manual Table 14. Current Function Specifications (continued) Accuracy1 Function

µA B (45 Hz to 2 kHz)

Range

Resolution

Model 832

Model 853, 4

Model 873, 4

Burden Voltage (typical)

400.0 µA 4000 µA

0.1 µA 1 µA

±(1.2% + 2)5 ±(1.2% + 2)5

±(1.0% + 2)5 ±(1.0% + 2)5

±(1.0% + 2) ±(1.0% + 2)

100 µV/µA 100 µV/µA

400.0 µA 4000 µA

0.1 µA 1 µA

±(0.4% + 4) ±(0.4% + 2)

±(0.2% + 4) ±(0.2% + 2)

±(0.2% + 4) ±(0.2% + 2)

100 µV/µA 100 µV/µA

µAF

1.

See the first sentence in Table 11 for a complete explanation of accuracy.

2.

AC conversion for Model 83 is ac coupled and calibrated to the rms value of a sinewave input.

3.

AC conversions for Models 85 and 87 are ac coupled, true rms responding, and valid from 5% to 100% of range.

4.

See note 3 in Table 11.

5.

Below a reading of 200 counts, add 10 counts.

46

Specifications Table 15. Capacitance and Diode Function Specifications Function

E

G 1.

Range

Accuracy1

Resolution

5.00 nF 0.0500 µF 0.500 µF 5.00 µF

0.01 nF 0.0001 µF 0.001 µF 0.01 µF

±(1% + 3) ±(1% + 3) ±(1% + 3) ±(1.9% + 3)

3.000 V

0.001 V

±(2% + 1)

With a film capacitor or better, using Relative mode to zero residual. See the first sentence in Table 11 for a complete explanation of accuracy.

Table 16. Frequency Counter Specifications Function Frequency (0.5 Hz to 200 kHz, pulse width >2 µs)

1.

Range

Resolution

199.99 1999.9 19.999 kHz 199.99 kHz >200 kHz

0.01 Hz 0.1 Hz 0.001 kHz 0.01 kHz 0.1 kHz

Accuracy1 ±(0.005% + 1) ±(0.005% + 1) ±(0.005% + 1) ±(0.005% + 1) unspecified

See the first sentence in Table 11 for a complete explanation of accuracy.

47

80 Series III Users Manual Table 17. Frequency Counter Sensitivity and Trigger Levels Minimum Sensitivity (RMS Sinewave) Input Range1 400 mV dc 400 mV dc 4V 40 V 400 V 1000 V

5 Hz - 20 kHz 70 mV (to 400 Hz) 150 mV 0.3 V 3V 30 V 300 V

0.5 Hz - 200 kHz

(DC Voltage Function) 40 mV  1.7 V 4V 40 V 400 V

70 mV (to 400 Hz) 150 mV 0.7 V 7 V (≤140 kHz) 70 V (≤14.0 kHz) 700 V (≤1.4 kHz)

Duty Cycle Range 0.0 to 99.9%

Approximate Trigger Level

Accuracy Within ±(0.05% per kHz + 0.1%) of full scale for a 5 V logic family input on the 4 V dc range. Within ±((0.06 x Voltage Range/Input Voltage) x 100%) of full scale for sine wave inputs on ac voltage ranges.

1.

48

Maximum input for specified accuracy = 10X Range or 1000 V.

Specifications Table 18. Electrical Characteristics of the Terminals

Overload Protection1

Input Impedance (nominal)

Common Mode Rejection Ratio (1 kΩ unbalance)

Normal Mode Rejection

L

1000 V rms

10 MΩ120 dB at dc, 50 Hz or 60 Hz

>60 dB at 50 Hz or 60 Hz

F mV

1000 V rms

10 MΩ120 dB at dc, 50 Hz or 60 Hz

>60 dB at 50 Hz or 60 Hz

K

1000 V rms

10 MΩ60 dB, dc to 60 Hz

Open Circuit

Full Scale Voltage

Function

Test Voltage

e

1000 V rms

350 ms and inputs >25% of range

1s

Same as specified accuracy for changes >2 seconds in duration

250 µs (Model 87 only)

Specified accuracy ±100 counts for changes >250 µs in duration (± 250 digits typical for mV, 400 µA dc, 40 mA dc, 4000 mA dc)

M BM80/2 Series Multi-Voltage Insulation and Continuity Tester

User Guide Guide de l’utilisateur Gebrauchsanleitung Guía del usuario

Contents Safety Warnings

2

Notes

3

General Description

4-5

Operation Testing is automatically inhibited if...

Insulation Testing Concepts Specification

6

11 12-13 14-17

Typical Terminal Voltage Characteristics 18

Voltage testing on high energy systems 6

Accessories

19

Auto-shut Off

6

Repair and Warranty

20

Insulation Tests (MΩ)

7

Polarization Index Testing

7

Mode d’emploi

22 - 43

Continuity Testing (Ω)

8

Betriebsanleitung

44 - 65

8

Instrucionnes de Uso

66 - 87

Continuity Bleeper (

)

Zeroing of Test Lead Resistance

8

Resistance Tests (kΩ)

9

Voltage Tests (V)

9

Live Circuit Warning

9

Battery Check (

1

Application Notes Preventive Maintenance

)

10

Battery Replacement

10

Fuse Checking and Replacement

10

• • • • •

• • •

SAFETY WARNINGS Safety Warnings and Precautions must be read and understood before the instrument is used. They must be observed during use. The circuit under test must be de-energized and isolated before connections are made except for voltage measurement. Circuit connections must not be touched during a test. After insulation tests, capacitive circuits must be allowed to discharge before disconnecting the test leads. The Live Circuit Warning and Automatic Discharge are additional safety features and should not be regarded as a substitute for normal safe working practice. Replacement fuses must be of the correct type and rating. Test leads, including crocodile clips, must be in good order, clean and have no broken or cracked insulation. U.K. Safety Authorities recommend the use of fused test leads when measuring voltage on high energy systems. NOTE THIS INSTRUMENT MUST ONLY BE USED BY SUITABLY TRAINED AND COMPETENT PERSONS.

2

Notes Symbols used on the instrument:

BEFORE USING THE INSTRUMENT, follow the separate instructions provided to fit either the locking or non-locking test button. Megger Limited recommend the fitting of the nonlocking test button. Hands free operation is provided on all ranges except the insulation ranges. If the locking button is fitted, extra care must be taken.

Risk of electric shock. Refer to User Guide. Equipment protected throughout by Double Insulation (Class II). Equipment complies with current EU Directives. NOTE

Users of this equipment and or their employers are reminded that Health and Safety Legislation require them to carry out valid risk assessments of all electrical work so as to identify potential sources of electrical danger and risk of electrical injury such as from inadvertent short circuits. Where the assessments show that the risk is significant then the use of fused test leads constructed in accordance with the HSE guidance note GS38 ‘Electrical Test Equipment for use by Electricians’ should be used.Users of this equipment and or their employers are reminded that Health and Safety Legislation require them to carry out valid risk assessments of all electrical work so as to identify potential sources of electrical danger and risk of electrical injury such as from inadvertent short circuits. Where the assessments show that the risk is significant then the use of fused test leads constructed in accordance with the HSE guidance note GS38 ‘Electrical Test Equipment for use by Electricians’ should be used. 3

General Description The BM80/2 Series instruments are battery powered Insulation and Continuity testers, with a measurement capability from 0,01 Ω Continuity to 200 GΩ Insulation. Offering multi-voltage facilities, the instruments take full advantage of microprocessor technology and feature a large liquid crystal display combining digital and analogue readings. The analogue display has the benefit of indicating trends and fluctuations in readings, while the digital readout gives direct accurate results. The BM80/2 Series instruments have the unique option of either a locking or non-locking button which is user selected. The chosen test button is easily pushed into the instrument casing without the use of a tool. The procedure for inserting the test button is provided on the separate instruction sheet included with the test buttons. A customized connector on the top of the instrument enables the optional Megger SP1 Switched probe to be used for two handed probe operation.

The TEST button is used to initiate the insulation tests, for operating the null facility and for adjusting the auto shut-off time. Grey markings on the range label denotes when the use of the TEST button is necessary. All other tests (Voltage, Continuity and Resistance) have the advantage of hands free operation and are activated when the probes make contact. The 250 V, 500 V and 1000 V ranges can be used to test electrical installations in compliance with BS7671 (16th Edition IEE Wiring Regulations) IEC364 and HD384, since each range has a 1 mA minimum test current at the minimum pass values of insulation specified in these documents. The 100 V range is ideal for testing telecommunications equipment which would be damaged by higher voltages. The 50 V range is useful for testing sensitive equipment, such as electronic components, and computer peripherals. Available as an optional accessory, the Megger DLB Downloading Base can be fitted for realtime downloading of measured test 4

General Description results to a Palmtop, Laptop or Personal computer via an RS232 serial lead. The optional miniature clip-on current transducer MCC10 enables the instrument to measure a.c. currents from 1 A to 10 A. Instrument power is supplied by six 1,5 V alkaline battery cells, which are constantly monitored. When battery power is nearly exhausted, the symbol appears on the display. Remaining battery life can be monitored at any time using the battery check switch position. This is beneficial before going on-site, to ensure enough battery power for the day’s work. Designed to IEC1010-1 the BM80/2 Series are protected against connection to a 440 V Category III supply. The instruments have a basic accuracy of ± 2% at 20 °C. The instruments are waterproof and dustproof to IP54. This helps maintain accuracy and ensures maximum reliability in harsh environments.

5

Operation The circuit under test must be completely de-energized and isolated before test connections are made.

Testing is automatically inhibited if...... •

An external voltage >55 V is present when switched to any Insulation position above 50 V.

•

An external voltage >25 V is present on all other ranges (excluding Voltmeter position).

The external voltage is indicated on the display and the bleeper sounds intermittently. Voltage Testing on High Energy Systems Use extreme care when using or measuring voltages above 30 V, particularly in high energy systems. Fused test leads are available as optional accessories. These are strongly recommended for use when making voltage tests. (GS38 H.S.E document).

Auto-shut Off To conserve battery life, Auto-shut Off (preceded by a series of bleeps) operates after 12 minutes of instrument inactivity in all insulation test switch positions, and after 5 minutes of instrument inactivity in all other switch positions. If desired, the 5 minute shutoff can be changed to 60 minutes (non insulation test switch positions). To do this, first perform a battery check, then press the TEST button twice to show (➔60). If an insulation test, or OFF is subsequently selected, the shut-off time reverts to the default times. It is therefore not possible to generate dangerous voltages for more than 12 minutes, even with a locking test button. To restore operation after Auto-shut Off, select OFF followed by the required switch position. Note: Auto-shut Off has a small power consumption and it is recommended that the instrument is switched to OFF when not in use. This is particularly important at the end of the working day, since no battery power is used in the OFF position. 6

Operation Insulation Tests (MΩ) Insulation tests operate only when the TEST button is pressed. (See the separate instructions for fitting the TEST button). These tests produce high voltages at the terminals and are initiated when the TEST button is pressed. When the TEST button is released, the reading will be held for a few seconds, the item under test will automatically be discharged, and the capacitive charge decay shown on the Live Circuit Warning voltmeter. When the 1 kV range has been selected (BM80/2 & BM82/2 only) and the TEST button pressed, there will be a safety delay of 3 seconds and ‘1000 V’ will flash before the test voltage is applied. This delay only occurs as a warning the first time that the button is pressed after the range has been selected. The delay will not occur on subsequent tests.

3. Press the TEST button to activate the test voltage. 4. Release the TEST button at the end of the test. The reading will hold for a few seconds. 5. Any capacitive circuits charged during a test will automatically discharge. If significant voltage remains the voltage warning will occur. 6. Remove the test leads only when no voltage is indicated.

test

Polarization Index Testing Polarization Index (PI) is the term applied to the Dielectric Absorption Ratio when resistance values are measured after 1 minute and again after 10 minutes. Polarization Index is then the resistance value after 10 minutes divided by the resistance value after 1 minute. The test can be run at any voltage.

2. Connect the test leads, first to the instrument, and then to the isolated item under test.

More detailed information on PI Testing and value assessment can be found in Megger Limited publications listed in the Accessories page.

1. Set the selector voltage required.

7

switch

to

the

Continuity Testing (Ω) (BM80/2 & BM81/2 only) The continuity tests are activated when the probes make contact. The test operates without the need to press the TEST button. When the test leads are removed the reading will hold for a few seconds and then reset. This range is not suitable for diode testing since the automatic contact detector will not be activated when connected to a diode. The kΩ range can be used for diode testing. 1. Set the selector switch to Ω. 2. Connect the test leads. The pointer will appear when connection to 1 V) ± 1% ±1 digit ± 2% ±1 digit ± 5% ±2 digits ± 2% ±2 digits

Default Voltmeter Operates at >25 volts a.c. or d.c. on any range except OFF and Battery check. Reverse polarity d.c. will cause '-dc' to appear in the display. 15

Safety Protection The instruments meet the requirements for double insulation to IEC 1010-1 (1995), EN 61010-1 (1995) to Category III**, 300 Volts phase to earth (ground) and 440 Volts phase to phase, without the need for separately fused test leads. If required, fused test leads are available as an optional accessory. E.M.C. In accordance with IEC 61326 including amendment No.1 Interference Error caused by 50/60 Hz hum: Insulation ranges (100 kΩ to ∞ ) Continuity range (0,2 Ω to 50 Ω)

20kA displayed if value exceeds 19,9kA). Earth Bond Testing By using the earth bond test lead available as an optional extra, the LT7 can measure the quality of Equipotential bonding within an installation. 1) Turn rotary switch to ‘Auto’ or ‘20Ω’. Firmly connect the flying lead probe to the metalwork to be tested 2) and plug the LT7 into a convenient installation socket. 3) Reading displayed will consist of socket supply (live conductor) impedance plus the impedance of the equipotential earth bonding.

SPECIFICATION Ranges: 20Ω (23A nominal)

0,01Ω - 19,9Ω ±2% ±3 digits (230 V supply) ±5% ±6 digits (110 V supply)

200Ω/2kΩ (15mA nominal) 1Ω -1,99kΩ When set to 0,1 Ω resolution

±2% ±1 digit (230 V supply) ±5% ±2 digits (110 V supply) ±2% ±3 digits (230 V supply) (±3 digits at 1s typical)

PSCC (23A nominal)

0,01 - 0,99 kA 1,0 - 19,9 kA Note: Calibration includes the test leads and plug. To maintain accuracy, these must not be changed. See note overleaf. Nominal System Voltage: 110 V / 230 V at 50 Hz Voltage Accuracy:

±2% ±2 digits (when L-PE neon indicates).

Power supply:

Auto shut off:

4 x 1,5 V Alkaline cells IEC LR6 type or 4 x 1,2 V NiCd or NiMH rechargeable cells After 5 minutes of instrument inactivity

Battery life:

Typically 1200, one minute tests

Low Battery Indicator:

The symbol will appear when Alkaline battery cells are almost exhausted. Note: Battery cells should not be left in an instrument which may remain unused for extended periods of time.

Display: Temperature Range: Operating: Storage:

3 digit L.C.D. -5˚C to 40˚C (0 - 90% RH non Condensing) -25˚C to 65˚C (0 - 95% RH non Condensing at 40˚C)

Thermal Protection:

Thermal cut-out will prevent overheating caused by repetitive testing on high current range.

Safety: Meets the requirements for double insulation to IEC 1010-1(1995) EN61010 (1995) at 230 V installation Category III*, without the need for separately fused test leads. If required, fused test leads are available as an optional accessory. *Relates to transient overvoltage likely to be found in fixed installation wiring. Fuses:

- Internal 10A (F) 440 V 10kA ceramic HBC - Mains power cord fused plug (when applicable): 10 Amp fuse to BS1362

E.M.C:

In accordance with IEC 61326 including amendment No.1

Note:

Overvoltage spikes may cause a reset to the original power ‘On’ state before reverting to normal operation.

Environmental Protection: Dimensions:

220 mm x 92 mm x 55 mm

Weight: Cleaning:

IP54

1200g (including leads, case & battery cells) Wipe disconnected instrument with a clean cloth dampened with soapy water or Isopropyl Alcohol (IPA).

ACCESSORIES Supplied

Part number

User Guide

6172-087

Power cord test lead with 3 pin plug to BS1363/A or Power cord test lead with CEE 7/7 plug

6231-601 6231-593

Dual test lead with probe

6231-591

Test-&-carry case

6420-092

Optional Test Lead Set red/balck

6220-437

Crocodile clip, black, for use with dual test lead

6280-284

Earth bond test lead with probe and 3 pin plug to BS1363/A

6231-586

Fused probe and clip set (2 probes and 3 clips) 1000 V max.10A fuse

6180-405

Power cord The power cord supplied with your LT7 forms part of the measuring circuit of the instrument. The overall length of this lead must not be altered. If the power cord plug is not suitable for your type of socket outlets, do not use an adaptor. You may change the plug once only by cutting the cord as close as possible and fitting a suitable plug. The colour code of the cord is: Earth (Ground)

Yellow / Green

Neutral

Blue

Phase (Line)

Brown

If using a fused plug, a 10 Amp fuse to BS 1362 should be fitted. Note: A plug severed from the power cord should be destroyed, as a plug with bare conductors is hazardous in a live socket outlet.

M RCDT300 Series Residual Current Device testers

USER MANUAL

G

SAFETY WARNINGS

■

Safety Warnings and Precautions must be read and understood before the instrument is used. They must be observed during use.

■

Continuity of protective conductors and earthed equipotential bonding of new or modified installations must be verified before carrying out RCD tests.

■

Do not leave the instrument connected to the mains supply when not in use.

■

Circuit connections and exposed metalwork of an installation or equipment under test must not be touched.

■

Ensure that hands remain behind guards of probes/clips when testing.

■

Do not move the rotary selector knob position while a test is in progress.

■

The instrument should not be used if any part of it is damaged.

■

Test leads, probes and crocodile clips must be in good order, clean and with no broken or cracked insulation.

■

The battery cover must be in place whilst conducting tests.

■

Voltage indicator LED’s cannot reveal a N-PE supply reversal.

NOTE THE INSTRUMENT MUST ONLY BE USED BY SUITABLY TRAINED AND COMPETENT PERSONS. Users of this equipment and/or their employers are reminded that Health and Safety Legislation requires them to carry out valid risk assessments of all electrical work so as to identify potential sources of electrical danger and risk of electrical injury such as inadvertent short circuits. Some national safety authorities recommend fused leads for voltage measurement on high energy systems. If RCD or Loop tests are made it may cause the fuse to rupture, and so they must be used with caution on voltage testing. 2

CONTENTS Safety warnings: Introduction General description Case contents LCD display Top panel Lid open/closure Preparations for use Batteries Preliminary test lead check General operating instructions Display warning symbols Setup procedure Reverse polarity detection Touch voltage Test leads Test lead connection. LED indicators Residual current device [RCD] testing RCD type selection 1/2I RCD non-tripping measurement 1xI & 5xI RCD trip time measurement 0 or 180° testing RampTest [RCDT320 and RCDT330 only] DC sensitive RCD test Programmable RCDs (RCDT330 only) Auto RCD test (RCD320 and RCDT330 only) Voltage measurement Touch voltage Frequency Hz (RCDT320 and RCDT330 only) Replacing batteries and fuses

2 4 4 5 6 6 7 8 8 8 8 9 9 9 9 10 10 11 11 12 12 12 13 13 13 13 13 15 15 17 17

Low battery warning symbol To replace batteries Fuse blown indication Preventive maintenance Specification Basic and service errors Accessories and equipment Repair and Warranty

17 17 18 19 19 21 21 22

Symbols used on the instrument are:

G t c

Caution: refer to accompanying notes Equipment protected throughout by Double Insulation (Class II) Equipment complies with current EU directives.

N1311

Equipment complies with ‘C tick’ requirements

3

INTRODUCTION Thank you for purchasing the Megger RCD Tester. For your own safety and to get the maximum benefit from your instrument, please ensure that you read and understand the following safety warnings and instructions before attempting to use the instruments.

GENERAL DESCRIPTION The RCDT300 Series test instruments have the following features: Feature 3 Phase safe

RCDT310 RCDT320 RCDT330 ■

■

■

■

■

■

■

Auto power down

■

■

■

Fuse blown indication

■

■

■

L-N-E polarity indicators

■

■

■

Voltmeter

■

■

■

■

■

This user manual describes the operation and functions of the following RCDT300 series of RCD testers:

Display backlight

RCDT310

Battery status indication

RCDT320 RCDT330

■

Frequency measurement Reverse polarity operation (can be disabled)

■

■

■

1/2I, I, 5I RCD trip time test

■

■

■

■

■

■

■

■

■

Auto sequence test Max touch voltage selectable (25/50 V)

■

RCD trip current test (RAMP)

4

0º/180º polarity selection

■

■

■

Selective breakers

■

■

■

CASE CONTENTS Feature DC breakers (1/2 I, I, 5I)

RCDT310 RCDT320 RCDT330 ■

■

Programmable breakers 30, 100, 300, 500 mA RCDs

■

■

10 mA/1000 mA RCD Plug ended test lead

■

■

2 wire test lead probe/croc clip ended

■

■

■

■

■

■

■

■

Calibration certificate

■

■

■

IEC61010-1 300V CATIII

■

■

■

EN61557

■

■

■

Results storage

■

Downloading

■

USB

■

Please complete the warranty card and return it to Megger Limited as soon as possible to help us reduce any delays in supporting you should the need arise. Carton contents RCDT310, RCDT320 and RCDT330: 1

x

RCDT300 series RCD tester

1

x

2 wire test lead with prods with clips (RCDT320, RCDT330 only)

8

x

AA (LR6) batteries (fitted in instrument)

1

x

Warranty card

1

x

Calibration certificate

1

x

CD containing user manual

1

x

Safety instructions

1

x

USB download lead (RCDDT330 only)

1

x

Download manager CD (RCDT330 only)

1

x

Printed quick start guide

1

x

Mains plug test lead

5

LCD DISPLAY

FRONT PANEL

Connection Panel RCDT300 Series test lead connections 6

STORE:.................... Store initiates the storing of a test result. LAST/NEXT:............ Selects the type of location; ie Job, distribution board, circuit, phase etc. ESC:......................... Aborts a save at any time. OK:.......................... Final operation to save the result.

▲ ▼

Selects the job, db, circuit number; ie 01,02,03 etc

Additional RCDT330 Controls Lid open/closure 1. Open lid by lifting up front panel tab (1). 2. Fold-away underneath instrument (2 & 3) and push into retaining slot (4).

Memory control keys:

Batteries The Megger RCDT300 series instruments are supplied with batteries 7

PREPARATIONS FOR USE (ALL INSTRUMENTS)

GENERAL OPERATING INSTRUCTIONS

fitted. When batteries become exhausted, refer to page 17, battery replacement.

The following condition may cause the instrument to inhibit testing:

Warning: Do not switch the instrument on with the battery cover removed. Preliminary test lead check Functional verification Before each use of the instrument, visually inspect the test leads, prods and crocodile clips to confirm that their condition is good, with no damaged or broken insulation.

Out of range supply voltage If an out of range voltage or frequency exists on the circuit under test, or on a very noisy mains supply, testing will be automatically inhibited. The RCD tests requires a minimum supply voltage to operate. If the warning 280V Indicates a supply voltage in excess of the allowed is present. 1999ms and the RCD should NOT trip. 7. Refer to the application note on Touch Voltage at the end of this section. NOTE: If the RCD should trip while performing a 1/2I test the error message ‘trP’ will be displayed instead of the time display.

1xI RCD trip time measurement To test the [1xI] trip time of the installed RCD:

AC Standard (displays ‘AC’) (Default)

1. Repeat the previous test for 1/2I, but with the bottom range knob set to I. The RCD trip indicator will display an open symbol .

AC Selective (displays ‘AC.S’)

2. The instrument should display the RCD trip time in milliseconds.

DC Sensitive (displays ‘dc’)

If the display shows >300 ms the RCD has failed to trip in the appropriate time. Check your test lead connections to the RCD and repeat the test.

DC Selective (displays ‘dc.S’)

If the RCD still fails to trip, suspect a faulty RCD. 1/2I RCD (Non-tripping) measurement To test the tripping time of the installed RCD under test: Range selection: 1. Connect the mains plug test lead or 2-wire Red/Green test lead to the instrument. 2. Plug in the mains plug test lead to the wall outlet, or the 2 wire test lead across the RCD (refer to connection drawing, go to page 10). 3. Set the top RCD selection knob to the correct range for the RCD under test. 4. Set the bottom range knob to [1/2I]. The RCD trip indicator will display a closed symbol . 5. Ensure the display shows the mains voltage. 12

Note: See also 0°/180° testing below. The RCD test may abort with “>25 V” or “>50 V” depending on touch voltage setting message if the loop resistance is so high that the test cannot proceed. 5xI RCD trip time measurement 1. Repeat the previous test for 1/2I, but with the bottom range knob set to 5xI. The RCD trip indicator should display an open symbol . 2. The instrument should display the RCD trip time in milliseconds. If the display shows >40 ms the RCD has failed to trip in the appropriate time. Check your test lead connections to the RCD and repeat the test.

If the RCD still fails to trip, suspect a faulty RCD.

used is 2 x the rated operating current of the RCD.

NOTE: The current limit for the 5I test is 100 mA, as the test current available is limited to 1 Amp.

As with the normal RCDs, these should be tested at 0° and 180°, or in the case of DC sensitive RCD’s, positive and negative.

0° or 180° testing Both the [1 x I] and [5 x I] tests should be performed for 0° and 180°.

Programmable RCD measurements

Repeat the 1 x I and 5 x I tests as above but with the instrument set to 180°. 0° or 180° is selected by pressing the [0°/180°] and the greatest trip time for each test recorded. RampTest (RCDT320 only) not programmable RCD The RCD trip current is measured by applying a test current of half the rated trip current and increasing this every 200 ms. When the RCD trips, the current flowing is recorded and displayed in mA.

To test a programmable RCD: 1. Select PROG on the top range knob. 2. Select 1/2I, I, 5I or AUTO. (Ramp test is not available in PROG mode) 3. Use the ↑↓ arrow keys to select the RCD trip current (range available from 10 mA to 1000 mA) and press OK. 4. Press TEST to start the RCD test.

1. Select the appropriate RCD rated current on the top range knob.

AUTO RCD test

2. Select the RAMP

3. Press the [TEST] test button

AUTO test will run the 1/2I, I & 5I plus 0º and 180º tests automatically. The operator can stand by the RCD to reset it when it trips on the I & 5I tests.

4. The RCD should trip and the trip current will be is displayed.

1. Connect to the circuit as per the 1/2I test above.

5. If the RCD fails to trip, >***mA is displayed where *** mA indicates the maximum RCD tripping current allowed and will vary depending on range selected.

2. Select the RCD current rating on the top range knob.

test on the lower range knob.

3. Select the AUTO function on the lower range knob. 4. Press the TEST button to start the test. The lock L symbol will flash to indicate a AUTO test sequence is running.

DC Sensitive RCD test [RCD ] D.C. sensitive RCDs are tested as per standard RCDs. The RMS current

5. The display will show ‘t1’ to ‘t5’ in the display to indicate which test the instrument is running.

13

6. Reset the RCD each time it trips.

Measurement results can be affected by the following:

7. On completion of testing, results can recalled by pressing the 0º/180º button.

1. Significant operating errors can occur if loads, particularly rotating machinery and capacitive loads are left connected during tests.

To indicate each test, segments of the bar graph are displayed as below:

2 A poor connection to the circuit under test.

none

= 1/2I test

I

= 1xI test

IIIII

= 5 I test

Example shows 5I on 0º

Possible sources of error 14

NOTE: Measured voltage should not exceed 300 V phase to earth.

VOLTAGE MEASUREMENT

TEST RESULT STORAGE (RCDT320 ONLY) How results are stored:

To measure the voltage of the electrical supply:

Results storage has the following structure:

1. Set the instrument to the [V] range. 2. Connect the GREEN OR (L0) lead to the protective Earth (PE) and the RED or (L1) lead to the phase to be measured. (Alternatively connect the mains plug test lead to a suitable mains outlet). 3. The instrument will display the Phase to Earth voltage.

000,

255

= Job number

b01,b02…

= Distribution board No.

c01, c02…

= Circuit number

L-E

= Circuit type (L-E only)

P1 to P3

= Phase

Touch Voltage On all Megger RCDT300 series testers, the touch voltage is calculated at the start of an RCD test to ensure it will remain below the safe 25 V or 50 V limit as required by the application. On the RCDT300 series instruments the touch voltage limit can be switched from 50 V to 25 V as the application demands. Should the touch voltage calculation identify a higher touch voltage than that permitted, the RCD tester will stop the test, thus preventing the presence of an unsafe voltage on the earth during the test, should the test have taken place. For those customers that require the touch voltage to be displayed, this can be displayed by activating the analogue arc display, as described in the instrument set-up procedure. Once activated the touch voltage will be displayed on an RCD test, even if the voltage is below the permitted limits.

Job number ( 000, 001…) acts as work folders. Sets of results can be saved to a particular job number and easily separated when downloaded. b01, b02… Distribution board number: c01, c02… Circuit reference Results can be assigned a specific distribution board number and circuit reference number. L-E

Test type: defines the circuit type (only L-E available on RCDT).

P1,P2,P3 Phase number: Each test can be stored under a particular phase, P1, P2 or P3. Unique test number: Each test result is assigned a unique test number, from 0 to 1999 logged automatically. This cannot be changed by the user. To store a result: 1. Select an RCD test mode and make a measurement as described earlier. 15

At the completion of the test press STORE. 2. Select Job reference number ( keys then press NEXT.

000,

3. Press OK and the test result will be displayed. 001 etc) using ↑↓

(Hold the key down to scroll quickly through the numbers) 3. Select distribution board number (b01,02 etc) using ↑↓ keys then press NEXT 4. Select circuit number (c01,02 etc) using ↑↓ keys then press NEXT 5. Circuit type is fixed at L-E, press NEXT 6. Select the Phase using ↑↓ keys then press NEXT. The screen will display a unique test number, which is attached to that particular test. 7. Press OK to save the result or ESC to abort.

Press the LAST or NEXT to scroll through all test parameters if applicable. NOTE: Only the last test result can be recalled to the display. Downloading results to a PC 1. Connect the tester to teh PC using the USB test lead. 2. Set the tester range knob to [Snd]. 3. Run Megger PowerSuite Professional or Megger Download Manager on the PC. 4. Select “Download from tester”. 5. The test data will automatically download its contents to the PC. A bar graph shows the status of the download.

Storing a subsequent result: To save the next test under the same location job number, distribution board etc:

Deleting test results To delete the latest test result;

1. Make another measurement as described earlier and press STORE.

1. Set the range knob to [dEL]. The display will flash "dEL" followed by the test number to be deleted.

2. The last Job number will be displayed. Press OK. 3. The unique test number will be displayed. Press OK and the result is stored. NOTE: To change any setting before saving a result, scroll down through the result using the NEXT/LAST keys. Change the reference number using the ↑↓ keys and press OK twice to store result. To recall the last test result: 1. Set the range knob to RCL 2. The last unique test number is displayed 16

2. Press the OK button. The last test result will be will be deleted. WARNING: This operation is not reversible. To delete all test data: 1. Set the range knob to [dEL]. The display will flash "dEL". 2. Press the NEXT or LAST key. The display will flash "ALL". 3. Press the OK button. All the test results will be deleted. A bar graph shows the progress of the deletion. WARNING: This operation is not reversible. All data will be deleted.

FREQUENCY HZ (RCDT320 ONLY)

REPLACING BATTERIES AND FUSES

To measure the frequency of the electrical supply:

Batteries Battery type:

1. Set the instrument to the [Hz] range. 2. Connect the GREEN or (L0) lead to the protective earth (PE) and the RED or (L1) lead to the phase to be measured. 3. The instrument will display the frequency in Hz.

8 x LR6 (AA), 1.5 V Alkaline, or 8 x 1.2V NiCAD, or 8 x 1.2V NiMH

Low battery warning symbol The battery condition is continuously displayed by the symbol When the batteries are exhausted, symbol will show and testing is inhibited.

.

If symbol appears as less than fully charged with new batteries, check for correct polarity. NOTE: Fully charged NiMH or NiCAD rechargeable batteries show a lower charge than Alkaline batteries, and may not give much warning before becoming exhausted. To replace batteries Warning: Do not switch the instrument on with the battery cover removed. 1. Switch off the instrument and disconnect (the instrument) from any electrical circuits. 2. The rear cover must not be opened if the test leads are connected. 3. To remove the rear cover release the screw at the bottom of the cover and lift the cover upwards. 4. Refit new batteries observing the correct polarity as marked on the battery compartment. 5. Replace the cover. NOTE: Battery cells should not be left in an instrument, which may remain unused for extended periods.

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Auto power-down To extend battery life the instrument will automatically switch off 6 minutes after the last operation. The instrument can be switch off manually be selecting [OFF] on the rotary switch, or switched back on by pressing the [TEST] button.

Fuse Blown indication

f

The fuse blown symbol indicates that an internal fuse has failed. This instrument is fitted with a factory fitted fuse and should only be replaced by an authorised Megger repairer. Contact your Megger distributor or call Megger Limited on 01304 502 102. Messages for information and warnings RCD test types AC AC.S DC DC.S

AC type AC selective RCD DC type RCD DC selective RCD

Warnings trp hot chk noS >50V >25V