Industrial Sensors PDF
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Industrial Electronics INDUSTRIAL, COMMERCIAL AND HOUSEHOLD SENSORS
Mendiola, Marie Grace L. BSECE- 4th year 5-6 MWF
Engr. Edwin L. Astorga, PECE
1. INDUSTRIAL SENSORS Mechanical Proximity sensors Essentially a mechanical switch • On/off operation only
– Normally Closed (NC)
• Two general modes
• Come in a wide variety of mechanical forms
– Normally Open (NO)
• For a wide range of use
When to Use Mechanical Proximity Switches • Where physical contact is possible • Where definitive position is required
• Where environment conditions preclude the use of optical or inductive sensors
• In operation-critical or safety-critical situations
Applications and Use of Mechanical Proximity Switches • Easy to integrate into machinery of all types
• Usually used as:
• Requires contact (thus wear)
– Limit switch
• Range of voltages: DC 0-1000V, AC, etc.
– Presence/absence indicator
• Very robust (explosion proof if required)
– Door closed/open
Optical Proximity Sensors • Consist of a light source (LED) and light detector (phototransistor)
• Modulation of signal to minimize ambient lighting conditions • Various models: 12-30V DC, 24-240V AC, power • Output: TTL 5V, Solid-state relay, etc.
Operational Modes • Through Beam:
– Long range (20m)
– Range 1-3m
– Alignment is critical !
– Popular and cheap
• Diffuse-reflective – Range 12-300mm – Cheap and easy to use
Applications of Optical Proximity Sensors
• Stack height control/box counting • Fluid level control (filling and clarity) • Breakage and jam detection • And many others…
Ultrasonic Proximity Sensors • Use sound pulses • Measures amplitude and time of flight • Range provides more than on/off information • Frequencies 40KHz-2MHz
When to use Ultrasonic Sensors • Provide range data directly: • Level monitoring of solid and liquids • Approach warning (collisions) • Can (usually) work in heavy dust and water • Ambient noise is potentially an issue
Inductive and Capacitive Proximity Sensors • Inductive sensors use change in local magnetic field to detect presence of metal target • Capacitive Sensors use change in local capacitance caused by non-metallic objects • Generally short ranges only • Regarded as very robust and reliable
When to use a Potentiometer • Pros – Require analog signal for control – Require absolute positional information – Low cost • Cons – Temperature and wear variations – Not in dusty or wet environments
Linear Variable Differential Transformer (LVDT) • An LVDT consists of a magnetic core that moves in a cylinder • The sleeve of the cylinder contains a primary coil that is driven by an oscillating voltage • The sleeve also contains two secondary coils that detect this oscillating voltage with a magnitude equal to displacement • The automatic nulling that can be achieved using two coils makes LVDTs very accurate (submillimetre)
Optical Encoders • Encoders are digital Sensors commonly used to provide position feedback for actuators • Consist of a glass or plastic disc that rotates between a light source (LED) and a pair of photo-detectors • Disk is encoded with alternate light and dark sectors so pulses are produced as disk rotates
Pressure • Pressure measured by: – Pitot tube and – Deformation of fixed membrane • Deformation measured using same methods as for force: • Spring (manometer) • Piezo distortion • Strain gauges
INSTALLATION Precision mounting of pressure sensors is essential for good pressure measurements. Although some mounting information is shown in this catalog, always check the installation drawings supplied in the manual with the sensor, or contact PCB to request detailed mounting instructions. Use good machining practices for the drilling and threading of mounting ports, and torque the sensors to the noted values. Mounting hardware is supplied with PCB sensors. Various standard thread adaptors are available to simplify some sensor installations. For free field blast applications, try to use “aerodynamically clean” mounts, minimizing unwanted reflections from mounting brackets or tripods. Also important is the avoidance of unusual side loading stresses and strains on the upper body of the sensor. Proper installation minimizes distortions in the output signal. A taut cable pulling at right angles to the electrical connector is an example of putting a side strain into the body. Another is the use of a heavy adaptor with cable attached to the small electrical connector in an environment with high transverse vibration. In some types of applications, such as free-field blast measurements, a pressure sensor mounted in a thin plate can be subjected to side loading stresses when the pressure causes the plate to flex. Use of an O-ring mount minimizes this effect.
2. COMMERCIAL SENSORS Wireless Sensor
Compatible with any Trane unit controller Includes sensor, receiver, wiring harness and two AA five-year lithium batteries Zone temperature is standard on all wireless sensors Temperature setpoint and occupied/unoccupied override provided with the WZS model Temperature setpoint is available in Fahrenheit or Celsius
Mounting the Receiver Back Plate Wiring the Receiver to the Unit Controller Power Requirements Wiring Procedure Replacing the Receiver Cover Applying Power to the ReceiverObserving the Receiver for Readiness to Associate Associating the Sensor to the Receiver Testing Signal Strength and Battery Status Mounting the Sensor Back PlateConfiguring the Wireless Sensor (Model WDS only) Configuration Procedure Replacing the Sensor Cover
CO2 Sensors When connected to a Tracer building management system and the appropriate ventilation equipment, the Trane Carbon Dioxide (CO2) sensor measures and records carbon dioxide in parts per million (ppm) in occupied building spaces. These carbon dioxide measurements are typically used to identify under-ventilated building zones and override outdoor air flow beyond design ventilation rates if the CO2 exceeds acceptable levels.
Combination Temperature and Humidity Sensors These sensors utilize a polymer capacitive sensing element, which provides superior performance and longevity. The polymer capacitive element has excellent recovery from saturation compared to other humidity sensing technologies.
Temperature Sensors It feature a full line offering that provides flexibility for building occupants to choose various temperature and operating mode setpoints to meet their comfort levels. Thermistor – Best value Platinum curve sensor – Most accurate Balco – Can be used with legacy controllers Configurations include Duct, Immersion, Averaging, Room, Flush Mount, Outdoor Air, Bullet, and Button sensors.
3. HOUSEHOLD SENSORS Temperature, Pressure, Humidity and Turbidity Sensor
Washing and Drying: The temperature sensor in washing machines allows precise control of water temperature (K276, Z276, Z278). A pressure sensor can be used to measure the level of water in the drum and the soiling of water can be determined by a turbidity sensor (Z407). In clothes dryers temperature sensors determine the temperature of hot air flowing into the drum (Z509, K514, K524) and that of the vented air (K276, Z276). To optimize anti-wrinkling treatment of laundry a temperature sensor can be integrated in the steam generator (K504, K514, K1560, K560). While embedded in the drum a humidity sensor detects the dampness of laundry to indicate how long it needs to dry.
Cooling and Freezing: Temperature sensors in refrigerators and freezers measure temperature of cooling compartment, guard against icing in the evaporator, and support ice cube preparation (M2000 and M3000 series, M1005), as well as detecting ambient temperature (M500)
Cooking: Temperature sensors are integrated into microwaves, stoves and ovens to detect chamber temperature (K514, K524, K554, M1703) as well as into the magnetrons of microwaves and on heat sinks (M1703). In addition, temperature sensors safeguard against overheating in induction hobs (K560, K1560).
Temperature and pressure sensor
Heating: Temperature sensors are integrated at various points in a heating system – in the forward and return flow of heating water or in the boiler, in the inflow and outflow of domestic hot water, in the exhaust to measure flue gas, in hot water tanks, in control units and thermostats to meter room temperature. In addition, pressure sensors can also serve to measure refrigerant pressure in heat pumps.