Endress+Hauser Profibus Planing Guide
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Guidelines for planning and commissioning
PROFIBUS DP/PA Field Communication
8
BA 034S/04/en/06.04 Nr. 56004242
PROFIBUS planning and commissioning
Table of Contents Revision History . . . . . . . . . . . . . . . . . 3 Registered Trademarks . . . . . . . . . . . . 3 1
Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.1 1.2 1.3
General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Conventions and icons . . . . . . . . . . . . . . . . . . . . . . 6 Documentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2
Introduction to PROFIBUS . . . . . . . . . . . . 8
2.1
2.4
PROFINET . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.1.1 Component-based Automation . . . . . . . . . 10 2.1.2 I/O integration . . . . . . . . . . . . . . . . . . . . . 12 PROFIBUS DP . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 2.2.1 Transmission standards . . . . . . . . . . . . . . . 15 2.2.2 PROFIBUS DP communication protocol . . . 16 2.2.3 Application profiles . . . . . . . . . . . . . . . . . . 19 2.2.4 PROFIsafe . . . . . . . . . . . . . . . . . . . . . . . . . 19 2.2.5 PROFIdrive . . . . . . . . . . . . . . . . . . . . . . . . 20 2.2.6 Integration technologies . . . . . . . . . . . . . . 21 2.2.7 Quality assurance . . . . . . . . . . . . . . . . . . . 21 PROFIBUS PA . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 2.3.1 Operating principle . . . . . . . . . . . . . . . . . . 24 2.3.2 Applications in hazardous areas . . . . . . . . . 25 Field Device Tool (FDT) . . . . . . . . . . . . . . . . . . . . 26
3
PROFIBUS DP basics . . . . . . . . . . . . . . . . 29
3.1 3.2 3.3 3.4 3.5
Synopsis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Topology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bus access method . . . . . . . . . . . . . . . . . . . . . . . . Network configuration . . . . . . . . . . . . . . . . . . . . . Applications in hazardous areas . . . . . . . . . . . . . . .
2.2
2.3
29 31 34 35 36
4
PROFIBUS PA Basics . . . . . . . . . . . . . . . . 38
4.1 4.2
Synopsis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Segment coupler and links . . . . . . . . . . . . . . . . . . . 4.2.1 Segment coupler . . . . . . . . . . . . . . . . . . . . 4.2.2 Link . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Topology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bus access method . . . . . . . . . . . . . . . . . . . . . . . . 4.4.1 Segment coupler . . . . . . . . . . . . . . . . . . . . 4.4.2 Gateway-type segment coupler . . . . . . . . . 4.4.3 Links . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Network Configuration . . . . . . . . . . . . . . . . . . . . . FISCO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fieldbus multi-drop barriers . . . . . . . . . . . . . . . . . .
4.3 4.4
4.5 4.6 4.7
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38 39 40 40 41 44 44 45 46 47 48 49
5
PROFIBUS PA Planning . . . . . . . . . . . . . 50
5.1 5.2 5.3 5.4
Selection of the segment coupler . . . . . . . . . . . . . . Cable type and length . . . . . . . . . . . . . . . . . . . . . . Current consumption . . . . . . . . . . . . . . . . . . . . . . . Voltage at last device . . . . . . . . . . . . . . . . . . . . . . . 5.4.1 Worst case calculation . . . . . . . . . . . . . . . . 5.4.2 Accurate calculation . . . . . . . . . . . . . . . . . Calculation examples for bus design . . . . . . . . . . . . 5.5.1 Example 1: Non-hazardous application . . . 5.5.2 Example 2: EEx ia application . . . . . . . . . . 5.5.3 Example 3: EEx ib application . . . . . . . . . . 5.5.4 Example: fieldbus barrier application . . . . . Data quantity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Addressing and cycle times . . . . . . . . . . . . . . . . . . 5.7.1 Addressing . . . . . . . . . . . . . . . . . . . . . . . . . 5.7.2 Cycle times . . . . . . . . . . . . . . . . . . . . . . . . 5.7.3 Example 1: Siemens segment coupler . . . . . 5.7.4 Example 2: Pepperl+Fuchs SK1 coupler . . . 5.7.5 Example 3: Pepperl+Fuchs SK2 coupler . . . 5.7.6 Example 4: Siemens PA link . . . . . . . . . . . .
5.5
5.6 5.7
50 51 52 54 54 55 56 56 58 60 63 64 68 68 68 69 70 71 73
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Installation PROFIBUS PA . . . . . . . . . . . 74
6.1 6.2 6.3 6.4 6.5 6.6
Cabling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Grounding and shielding . . . . . . . . . . . . . . . . . . . . Termination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Overvoltage protection . . . . . . . . . . . . . . . . . . . . . . Installation of the devices . . . . . . . . . . . . . . . . . . . . Setting addresses . . . . . . . . . . . . . . . . . . . . . . . . . . 6.6.1 Using DIP switches . . . . . . . . . . . . . . . . . . 6.6.2 Software addressing with FieldCare . . . . . . 6.6.3 Software addressing with Commuwin II . . .
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System Integration . . . . . . . . . . . . . . . . . . 85
7.1
Network configuration . . . . . . . . . . . . . . . . . . . . . . 85 7.1.1 Tested systems . . . . . . . . . . . . . . . . . . . . . . 86 Device database files (GSDs) . . . . . . . . . . . . . . . . . 87 7.2.1 GSD file example . . . . . . . . . . . . . . . . . . . . 89 7.2.2 Full configuration with manufacturer-specific GSDs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90 7.2.3 Partial configuration with manufacturer-specific GSDs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92 7.2.4 Profile GSD . . . . . . . . . . . . . . . . . . . . . . . . 93 Cyclic data exchange . . . . . . . . . . . . . . . . . . . . . . . 94 7.3.1 Status codes: Device status BAD . . . . . . . . 95 7.3.2 Status code: Device status UNCERTAIN . . . 96 7.3.3 Status codes: Device status GOOD . . . . . . . 97 Bus parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . 99 7.4.1 Aligning FieldCare . . . . . . . . . . . . . . . . . . 100 7.4.2 Aligning Commuwin II . . . . . . . . . . . . . . 100 7.4.3 Commissioning the Pepperl+Fuchs SK2 . . 101 7.4.4 Watch Dog Time TWD . . . . . . . . . . . . . . . . . . 103
7.2
7.3
7.4
74 75 79 79 80 82 82 83 84
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PROFIBUS planning and commissioning
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Device Parametrization . . . . . . . . . . . . 104
8.1 8.2
PROFIBUS PA block model . . . . . . . . . . . . . . . . . PROFIBUS PA profile . . . . . . . . . . . . . . . . . . . . . 8.2.1 Block structure . . . . . . . . . . . . . . . . . . . . 8.2.2 Device management . . . . . . . . . . . . . . . . 8.2.3 Transmitter and actuator blocks . . . . . . . 8.2.4 Analysis devices . . . . . . . . . . . . . . . . . . . 8.2.5 Function overview . . . . . . . . . . . . . . . . . FieldCare Asset Management . . . . . . . . . . . . . . . 8.3.1 Using FieldCare . . . . . . . . . . . . . . . . . . . 8.3.2 Generation of a live list . . . . . . . . . . . . . . 8.3.3 Device parametrization . . . . . . . . . . . . . . 8.3.4 On-line parametrization . . . . . . . . . . . . . 8.3.5 Plant View . . . . . . . . . . . . . . . . . . . . . . . Commuwin II Operating Program . . . . . . . . . . . . 8.4.1 Operation . . . . . . . . . . . . . . . . . . . . . . . . 8.4.2 Device menu . . . . . . . . . . . . . . . . . . . . .
8.3
8.4
105 106 108 109 110 113 114 116 117 118 118 119 119 120 120 121
9
Trouble-Shooting . . . . . . . . . . . . . . . . . 122
9.1 9.2 9.3 9.4
Commissioning . . . . . . . . . . . . . . . . . . . . . . . . . . PLC planning . . . . . . . . . . . . . . . . . . . . . . . . . . . Data transmission . . . . . . . . . . . . . . . . . . . . . . . . Commuwin II . . . . . . . . . . . . . . . . . . . . . . . . . .
10
Technical Data . . . . . . . . . . . . . . . . . . . . 125
10.1 10.2
PROFIBUS DP . . . . . . . . . . . . . . . . . . . . . . . . . . 125 PROFIBUS PA . . . . . . . . . . . . . . . . . . . . . . . . . . 126
11
PROFIBUS Components . . . . . . . . . . . 127
11.1 11.2 11.3 11.4 11.5
Endress+Hauser field devices PROFIBUS PA . . . . Endress+Hauser field devices PROFIBUS DP . . . . Network components . . . . . . . . . . . . . . . . . . . . . Asset management and operating software . . . . . Supplementary documentation . . . . . . . . . . . . . .
12
Terms and Definitions . . . . . . . . . . . . . 164
12.1 12.2 12.3 12.4
Bus architecture . . . . . . . . . . . . . . . . . . . . . . . . . Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . Data exchange . . . . . . . . . . . . . . . . . . . . . . . . . . Miscellaneous terms . . . . . . . . . . . . . . . . . . . . . .
13
Appendix: Calculation Sheets . . . . . . 168
13.1 13.2 13.3
Explosion hazardous areas EEx ia . . . . . . . . . . . . 168 Explosion hazardous areas EEx ib . . . . . . . . . . . . 170 Non-hazardous areas . . . . . . . . . . . . . . . . . . . . . 172
2
122 123 123 124
127 153 160 162 163
164 165 166 167
Endress+Hauser
PROFIBUS planning and commissioning
Revision History Issue
Changes
BA198F/00/en/11.99
Original Version
BA034S/04/en/07.04
Revision of manual to include latest information on PROFIBUS standard Additional descriptions of new components Revision of device techniical data
Registered Trademarks • PROFIBUS® is a registered trademark of PROFIBUS User-Organisation e.V., Karlsruhe, Germany • Microsoft®, Windows®, Windows NT®, Windows 2000®,Windows XP® are registered trademarks of Microsoft Corporation, Redmond, Washington, USA
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PROFIBUS planning and commissioning
Approved usage
1 Safety
1
Safety
1.1
General
These guidelines have been written with the view of giving the potential PROFIBUS user an introduction to the planning and commissioning of a PROFIBUS PA network. They are based on the experience of Endress+Hauser employees who have been actively involved in PROFIBUS projects and who, in the meantime, have successfully commissioned a large number of plants. The approved usage of the individual devices that are used in a network can be taken from the corresponding device operating instructions.
Installation, commissioning, operation
The field devices, segment coupler, cables and other components must be designed to operate safely in accordance with current technical safety and EU standards. If installed incorrectly or used for applications for which they are not intended, it is possible that dangers may arise. For this reason, the system must be installed, connected, operated and maintained according to the instructions in this and other relevant manuals: personnel must be authorised and suitably qualified.
Explosion hazardous area
If the system is to be installed in an explosion hazardous area: • Ensure that all personnel are suitably qualified • Observe the specifications in the certificate • Observe any national and local regulations. For PROFIBUS PA, it is recommended components should be designed in accordance with the FISCO model. This greatly simplifies the acceptance testing of the PROFIBUS PA segment. Where another scheme is used, e.g. Exe/Exi multibarriers, proof of intrinsic safety must be furnished.
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1 Safety
PROFIBUS planning and commissioning
1.2
Conventions and icons
In order to highlight safety relevant or alternative operating procedures in the manual, the following conventions have been used, each indicated by a corresponding icon in the margin. Safety conventions
. Icon
Meaning A note highlights actions or procedures which, if not performed correctly, may indirectly affect operation or may lead to an instrument response which is not planned
Caution! Caution highlights actions or procedures which, if not performed correctly, may lead to personal injury or incorrect functioning of the instrument Warning! A warning highlights actions or procedures which, if not performed correctly, will lead to personal injury, a safety hazard or destruction of the instrument
Explosion protection
. Icon
Meaning Device certified for use in explosion hazardous area If the device has this symbol embossed on its name plate it can be installed in an explosion hazardous area in accordance with the specifications in the certificate or in a safe area Explosion hazardous area Symbol used in drawings to indicate explosion hazardous areas. Devices located in and wiring entering areas with the designation “explosion hazardous areas” must conform with the stated type of protection Safe area (non-explosion hazardous area) Symbol used in drawings to indicate, if necessary, non-explosion hazardous areas. Devices located in safe areas stiill require a certificate if their outputs run into explosion hazardous areas.
Electrical symbols
. Icon
Meaning Direct voltage A terminal to which or from which a direct current or voltage may be applied or supplied
Alternating voltage A terminal to which or from which an alternating (sine-wave) current or voltage may be applied or supplied Grounded terminal A grounded terminal, which as far as the operator is concerned, is already grounded by means of an earth grounding system Protective grounding (earth) terminal A terminal which must be connected to earth ground prior to making any other connection to the equipment Equipotential connection (earth bonding) A connection made to the plant grounding system which may be of type e.g. neutral star or equipotential line according to national or company practice
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1.3
1 Safety
Documentation
The guidelines are structured as follows:
Endress+Hauser
Chapter
Title
Content
Chapter 1
Introduction
Advantages of a bus as well as general information about the PROFIBUS standard
Chapter 2
Introduction PROFIBUS
An overview of PROFIBUS standards for factory and process automation
Chapter 3
PROFIBUS DP Basics
Information about PROFIBUS DP
Chapter 4
PROFIBUS PA Basics
Information about PROFIBUS PA, couplers, links and use in explosion hazardous areas (FISCO-Model)
Chapter 5
PROFIBUS PA Planning
What must be observed when planning PROFIBUS DP/PA systems, with examples
Chapter 6
PROFIBUS PA Installation
Notes on the installation of devices in a PROFIBUS DP/PA system
Chapter 7
System Integration
Notes on mapping PROFIBUS PA devices in a PLC
Chapter 8
Device Configuration
General information on setting the parameters in Endress+Hauser devices PROFIBUS applications
Chapter 9
Trouble-Shooting
Causes and remedies for general faults that may occur during the commissioning of a system
Chapter 10
Technical Data
Principle technical data of PROFIBUS PA and PROFIBUS DP
Chapter 11
PROFIBUS Components
Profiles of the Endress+Hauser PROFIBUS DP and PROFIBUS PA devices
Chapter 12
Terms and Definitions
Explanation of the terminology used to describe bussystems
Chapter 13
Appendix
Calculation sheets for your applications
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2 Introduction to PROFIBUS
PROFIBUS planning and commissioning
2
Introduction to PROFIBUS
PROFIBUS is a standardized, open communications system for all areas of application in factory and process automation. The technology was introduced in the early 1990s and has been developed continuously ever since. The PROFIBUS DP and PROFIBUS PA technologies are specified in the international standards EN 50170 and IEC 61158 and are suitable for replacement of discrete and analog signals in control systems. PROFIBUS DP
The original specification was aimed primarily at the requirements of Factory Automation, but this was quickly extended to include the requirements of process automation, in particular the need for intrinisically safe bus powering of devices. This is mirrored in the PROFIBUS PA specifications. As its popularity increased, the PROFIBUS DP specifications were extended to include a number of common but optional application profiles for e.g. safety, time stamping etc.. Similarly several application profiles were developed to meet the needs of specific device types, e.g. measuring devices, drives, remote I/O etc.. By the turn of the century, the PROFIBUS DP/PROFIBUS PA standard had covered many of the requirements of both Factory and Process Automation from field to control level - as shown by Fig. 2-1. It was rewarded by a large degree of support from both equipment manufactures and users, and today has an installed base of over 10,000,000 I/0 points.
OS
ES Internet OPERATIONS: PROFINET
Ethernet TCP/IP
IPC
PLC
MBP (IEC 61158-2)
RS-485/FO
12:00
14:00
16:00
18:00
20:00
22:00
HART, ASi FACTORY: PROFIBUS DP
PROCESS: PROFIBUS DP
Fig. 2-1: Overview of PROFIBUS technologies
PROFINET
At this point in time, however, Ethernet had already begun to work its way down from the office environment on to the factory floor, and was being seen as the future standard for control system backbones. Office Ethernet is in itself not suitable for control systems, since media access is stochchastic (CSMA/CD), not deterministic, so there was a need to develop a further standard for the operations level. The result is the PROFINET specification, which not only addresses the problems of deterministic control for real time and isochronic real time applications, but also those of network engineering, operation and I/O integration of control and fieldbus networks. PROFINET is only just at the beginning of its development, but promises many exciting solutions for the future.
PROFIBUS User Organisations
PROFIBUS is supported by PROFIBUS International, which is a world-wide association of PROFIBUS user organisations. It is responsible for the development of the standard, its maintenance, the conformance testing of PROFIBUS devices as well as the issuing of device certificates. It has a number of independent accredited PROFIBUS Competence Centers thoughout the world (one is located Endress+Hauser Process Solutions AG) which maintain test facilities that are accessible for users and offer training courses for prospective PROFIBUS engineers.
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2.1
2 Introduction to PROFIBUS
PROFINET
As can be seen from Fig. 2-1, PROFINET is the Ethernet-based automation standard of PROFIBUS International. It intended for use in a wide range of industrial applications, for example in: • • • • •
Production systems Assembly systems Systems in the automotive industries Systems in the food and beverage industries Packaging systems
PROFINET allows the implementation of distributed automation structures, integration of simple decentralized field devices as well as the operation of motion control applications. As can be seen in Fig. 2-2, each of these applications places different demands on the system with regard to response times and real time operation.
Internet
Controller and HMI
Field Devices
100ms TCP/IP
Motion Control
10ms Real Time
0.34 mm², corresponds to AWG 22
Cable type
twisted pairs, 1x 2, 2x 2 or 1x 4 core
Loop resistance
110 Ω per km
Signal attenuation
max. 9 dB over the entire length of the segment
Screening
woven copper sheath or woven sheath and foil sheath Table 3-3: Specifications of Cable Type A
Structure
The following points should be noted when the bus structure is being planned: • The max. permissible cable length depends upon the transmission rate. For PROFIBUS RS-485 cable of type A (see table 2.3) the dependency is as follows: Transmission rate (kBit/s)
9.6; 19.2; 45.45; 93.75
187.5
500
1500
3000; 6000; 12000
Cable length (m)
1200
1000
400
200
100
• • • •
A maximum of 32 participants per segment is allowed A terminating resistance must be installed at both ends of every segment (ohmic load 220 Ω) The cable length and/or the number of participants can be increased by using repeaters If repeaters are used: – The first and last segment may contain up to 31 particpants, the segments between repeaters may contain up to 30 participants. – The maximum distance between two participants is: (NO_REP +1) * Segment length where = NO_REP = max number of repeaters that may be used in series (dependent on type).
Example: According to a manufacturer’s specifications, up to 9 repeaters can be connected in series on a standard line. The maximum distance between two bus participants for a transmission speed of 1.5 MBit/s is thus: (9+1)*200 m = 2000 m
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3 PROFIBUS DP basics
Spurs
A spur is the cable connecting the field device to the T-box on the bus.
" Examples
PROFIBUS planning and commissioning
Caution! As a rule of thumb: • For transmission rates up to 1.5 MBit/s, the total length (sum) of the spurs may not exceed 6.6 m • Spurs should not be used for transmission rates greater than 1.5 MBit/s. Figs 3-2 and 3-3 show examples for a linear and tree bus structure. • Fig 3-2. shows that three repeaters are necessary if the PROFIBUS DP system is to be developed to the full. The maximum cable length corresponds to 4x the value quoted in the table above. Since three repeaters are used, the maximum number of participants is reduced to 120. • Fig 3-3 shows how several repeaters can be used to create a tree structure. The number of participants allowable per segment is reduced by one per repeater.
Fig. 3-2: PROFIBUS DP-system with linear structure (T = terminator, R = repeater, 1...n = max. number of field devices on a segment)
Fig. 3-3: PROFIBUS DP-system with tree structure (T = terminator, R = repeater, 1...n = max. number of field devices on a segment)
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Optical network
3 PROFIBUS DP basics
If the PROFIBUS DP system has to be routed over large distances or in plant with heavy electromagnetic interference, then an optical or mixed optical/copper network can be used. Provided that all participants support them, very high transmission rates are possible. Fig. 3-4 shows a possible structure for an optical network, whereby the technical details can be taken from the PROFIBUS standard.
Master (PLC)
RS 485 copper
optical interface modulel
optical interface module
fibre optics
Fig. 3-4: Example for a mixed optical/RS-485-network (T = terminator, 1...n = field devices (slaves)
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3 PROFIBUS DP basics
PROFIBUS planning and commissioning
3.3
Bus access method
PROFIBUS DP uses a hybrid access method of centralised master/slave and decentralised token passing, see Fig. 3-5. The masters build a logical token ring. • When a master possesses the token, it has the right to transmit. • It can now talk with its slaves in a master-slave relationship for a defined period of time. • At the end of this time, the token must be passed on to the next active device in the token ring. Master class
PROFIBUS DP version DP-V1 differentiates between two classes of master: • A Class 1 master communicates cyclically with its slaves. The master communicates only with those slaves that are assigned to it. A slave may be assigned to only one Class 1 master. A typical class 1 master is a programmable logic controller (PLC) or a process control system. • A Class 2 master communicates acyclically with its slaves, i.e. on demand. Its slaves may also be assigned to a Class 1 master. A typical example is a PC with corresponding operating software, e.g. FieldCare - Plant Asset Management Tool. It is used for commissioning as well as for device configuration, diagnosis and alarm handling during normal operation. If a PROFIBUS-DP network has more than one master e.g. because both cyclic and acyclic services are required, then it is a multi-master system. If, for example, a PLC only is used for control tasks, then the system is a mono-master system. Master 1, Class 1 has the right to transmit. Data are exchanged cyclically.
Master 2, Class 2 receives the right to transmit. It can talk to all slaves. Data exchage, e.g. with slave 3 is acyclic.
Class 1
logical token ring between master participants
Class 2
Fig. 3-5: Data exchange in a PROFIBUS DP-multi-master system (M = master, S = slave)
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3.4 Data transmission
3 PROFIBUS DP basics
Network configuration
Data are exchanged over PROFIBUS DP by means of standard telegrams which are transmitted via the RS-485 interface. The permissible telegram length of reference data is specified in the PROFIBUS DP protocol at 244 bytes. it should be noted, however, that some controllers only support an maximum telegram length of 122 bytes. The PROFIBUS DP devices manufactured by Endress+Hauser may transmit both input and output values, see also Table 5.17. In general: • Measured value and status inputs are transmitted in 5 bytes. • Display values and status outputs are transmitted in 5 bytes • Control output values generally require 1 byte per action, the actual number available being dependent upon device. An instrument with several measured values can transmit correspondingly more bytes. In the case of the flowmeter Promass 63, for example, a cyclic telegram up to 37 bytes (25 bytes input and 12 byte output data) is transmitted at maximum configuration, see Section 3.4.2. The values to be transmitted are determined during the commissioning of the network. The total number of inputs and outputs enabled then determine the telegram length. The same telegram is used for transmission to and from the PLC.
GSD (device database file)
In order to integrate the field devices into the bus system, the PROFIBUS DP system requires a description of the device parameters such as output data, input data, data format, data length and the transmission rates supported. These data are contained in the GSD device database file, which is required by the PROFIBUS DP master during the commissioning of the communication system. In addition, device bit maps are required, which appear as icons in the network tree. Further information on device database files is to be found in Chapter 7.2.
Bus address
A prerequisite for communication on the bus is the correct addressing of the participants. Every participant in the PROFIBUS DP system is assigned a unique address between 0 and 125 (cyclic data transmission). Normally the low addresses are assigned to the masters. The addresses may be assigned by DIP switch, on-site operating elements or by an operating program, e.g. FieldCare. The exact way in which this is done should be taken from the appropriate device manual. For Endress+Hauser devices, the factory default address is always 126. This must be changed during commissioning and no device in the system should use it for cyclic communication.
Transmission rate
All participants in a PROFIBUS DP system must support the governing transmission rate. This means that the speed of data exchange is determined by the slowest participant. In the case of Endress+Hauser devices that are designed for PROFIBUS DP, all transmission rates from 9.6 kbits/ s to 12 Mbit/s are supported. For other manufacturers, please consult the relevant operating manual.
Bus parameters
In addition to the transmission rate, all active participants on the bus must operate with the same bus parameters. If FieldCare is in use, the bus parameters can be set by using the corresponding Communication DTM for PROFIBUS. Individual device rates are set within their DTMs. More information on bus parameters are to be found in the Chapter 4.
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3 PROFIBUS DP basics
PROFIBUS planning and commissioning
3.5
Applications in hazardous areas
All devices and terminators that are installed in hazardous areas as well as all associated electrical apparatus (e.g. PA links or segment couplers) must be approved for the corresponding atmospheres. RS-485 IS
RS-485 IS is a recent innovation in response to an increasing market demand for the use of RS-485 in explosion-hazardous areas. A corresponding PROFIBUS guideline is now available that specifies the configuration of intrinsically safe RS-485 solutions with simple device interchangeability. In contrast to the FISCO model (see Chapters 2.2.1 and 6.1), for which there is only one active supply device per segment, all stations represent active sources. The devices are supplied with external energy and can supply this to the bus. RS-485 IS segments are coupled to RS-485 safe segments by means of so-called "Fieldbus Isolating Repeaters". Up to 32 stations can be connected to the intrinsically safe bus circuit, provided the conditions in Table 3-7 arre upheld. More details can be found in the specification. Endress+Hauser devices do not support RS-485 IS at the present moment, but offers equivalent solutions with standard devices. The following table shows all safety-relevant values for the entire bus system. Parameter
Description
Value
Maximum input voltage
Ui [V]
± 4.2
Maximum input current
Ii [A]
4.8
Maximum inductance to resistance ratio
L ’/R’ [µH/Ω]
15
Number of devices
NTN
≤ 32
Maximum output voltage
Uo [V]
± 4.2
Maximum output current
Iο [mA]
149
Maximum input voltage
Ui [V]
± 4.2
Maximum internal inductance
Li [H]
0
Maximum internal capacitance
Ci [nF]
N/A
Maximum output voltage
Uo [V]
± 4.2
Maximum output current
Iο [mA]
16
Maximum input voltage
Ui [V]
± 4.2
Maximum internal inductance
Li [H]
0
Maximum internal capacitance
Ci [nF]
N/A
Remarks
Bus system
For the whole operation Temperaturee range of the bus system
Communication device
Total current from wires A, B and supply for bus termination
Insignificant for safety
External active bus termination
Insignificant for safety
Table 3-4: PROFIBUS RS_485 IS: list of safety-relevant parameters
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3 PROFIBUS DP basics
If a PROFIBUS DP segment runs through an explosiion hazardous area, it must be executed with a degree of protection "increased safety" "e". • For copper cabling, the number of devices per segment is limited to four. • Proof of instrinsic safety is required for every segment, since every intrinsically safe component has different electrical characteristics. • The cable and spurs must be included in the calculation. • Exchange of a component from one manufacturer by a component from another manufacture is always requires renewed proof of intrinsic safety. Mixed network PROFIBUS DP/PA
Since PROFIBUS PA systems are designed for use in hazardous areas, it is much easier install a segment there. For this reason, a PROFIBUS PA segment is used to extend the PROFIBUS DP segment into a hazardous area. PROFIBUS PA networks are connected to PROFIBUS DP networks by a segment coupler or link, see Chapter 3.2.
PLC Class 1 master
PROFIBUS PA
segment coupler / link
e.g. FieldCare Class 2 master
PROFIBUS DP
PROFIBUS DP-Slaves
PROFIBUS PA-Slaves
Fig. 3-6: The PROFIBUS DP system can be extended into a hazardous area by using a segment coupler/link.
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4
PROFIBUS PA Basics
This chapter presents the basic principles behind PROFIBUS PA. It is structured as follows: • • • • • • • • •
4.1 Application
Synopsis Segment couplers and links Topology Bus access method Network configuration Applications in hazardous areas Operating mode FISCO Fieldbus barriers
Synopsis
PROFIBUS-PA has been designed to satisfy the requirements of process engineering. There are three major differences to a PROFIBUS DP system: • PROFIBUS PA supports the use of devices in explosion hazardous areas without the need for specific proof of intrinsic safety. • The devices can be powered over the bus cable (two-wire devices). • The data are transferred via the IEC 61158-2 physical layer (MBP), which allows great freedom in the selection of the bus topology. The most important technical data are listed in Table 4-1.
Participants
Depending upon the application, the participants on a PROFIBUS PA segment might be actuators, sensors and a segment coupler or link, see Chapter 4.2. Endress+Hauser offers PROFIBUS PA instrumentation for the most important process variables, i.e. analysis, flow, level, pressure and temperature. A complete list is to be found in Chapter 10.
PLC Class 1 master
DP/PA link or segment coupler
e.g. FieldCare Class 2 master
PROFIBUS DP
PROFIBUS PA
PROFIBUS PA-Slaves
Fig. 4-1: PROFIBUS PA-system
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Standard
IEC 61158
Support
PROFIBUS User Organisation (PNO)
Physical layer
IEC 61158-2, Mancester Coding Bus Powered (MBP)
Max. length from segment coupler
1900 m: Standard- und eigensichere Anwendungen der Kategorie ib 1000 m: Eigensicheren Anwendungen der Kategorie ia
Participants
max. 10 in hazardous areas (EEx ia) max. 24 in hazardous areas (EEx ib) max. 32 in safe areas
Transmission rate
31.25 kBit/s
Bus access method
Master-slave
Protocol
DP-V1 Table 4-1: Technical data PROFIBUS PA
4.2
Segment coupler and links
PROFIBUS PA is always used in conjunction with a supervisory PROFIBUS DP control system. Since the physical layer and transmission rates of PROFIBUS DP and PROFIBUS PA are different, see Tables 3-1 and 4-1, the PROFIBUS PA segment is connected to the PROFIBUS DP system via a segment coupler or link. Segment couplers are signal converters that modulate the RS485 signals to the MBP signal level and vice versa. They are transparent from the bus protocol standpoint. In contrast, links have their own intrinsic intelligence. They map all the field devices connected to the MBP segment as a single slave in the RS485 segment.
PLC Class 1 master
e.g. FieldCare Class 2 master
PROFIBUS DP
segment coupler / link segment coupler
segment coupler PROFIBUS PA
junction box
Fig. 4-2: Integration of a PROFIBUS PA segment into a PROFIBUS DP system using a segment coupler or link
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4.2.1
Segment coupler
A segment coupler comprises a signal coupler and bus power unit. Depending upon model, they may support a fixed or a range of transmission rates on thePROFIBUS DP side. The transmission rate for PROFIBUS PA is fixed at 31.25 kbit/s. Three types of segment couplers have been specified according to the type of protection required. Segment coupler
Type A
Type B
Type C
Type of protection
EEx [ia/ib] IIC
EEx [ib] IIB
None-Ex
Supply voltage
13.5 V
13.5 V
24 V
Max. power
1.8 W
3.9 W
9.1 W
Max. supply current
≤ 110 mA
≤ 280 mA
≤ 400 mA
No. of devices
ca. 10
ca. 20
max. 32
Table 4-2: Segment couplers defined in standard
At the moment two manufacturers have segment couplers available: Manufacturer / Model
Description
Type of protection
Supply current
Voltage
DP-baudrate
Pepperl+Fuchs SK1
KFD2-BR-1.PA.2
Non-Ex
380 mA
22.0 V DC
93.75 kBit/s
Pepperl+Fuchs SK1
KFD2-BR-1.PA.93
Non-Ex
400 mA
24.0-26,0 V DC
93.75 kBit/s
Pepperl+Fuchs SK1
KFD2-BR-EX1.PA
EEx [ia] IIC
100 mA
12.6-13.4 V DC
93.75 kBit/s
Pepperl+Fuchs SK1
KFD2-BR-EX1.2PA.93
EEx [ia] IIC
100 mA
12.6-13.4 V DC
93.75 kBit/s
Pepperl+Fuchs SK1
KFD2-BR-EX1.3PA.93
EEx [ia] IIC
100 mA
12.6-13.4 V DC
93.75 kBit/s
Pepperl+Fuchs SK2
KLD2-PL(2)-1.PA
Non-Ex
400 mA
24,0-26,0 V DC
45.45 kBit/s 12 MBit/s*
Pepperl+Fuchs SK2
KLD2-PL(2)-EX1.PA
EEx [ia] IIC
100 mA
12.8 - 13.4 V DC
45.45 kBit/s 12 MBit/s*
Siemens DP/PA-coupler
6ES7157-0AC80-0XA0
Nicht-Ex
400 mA
19.0 V DC
45.45 kBit/s**
Siemens DP/PA-coupler
6ES7157-0AD00-0XA0
EEx [ia] IIC
90 mA
12.5 V DC
45.45 kBit/s**
Siemens DP/PA-coupler
6ES7157-0AD80-0XA0
EEx [ib] IIC
110 mA
12.5 V DC
45.45 kBit/s**
Siemens DP/PA-coupler
6ES7157-0AD81-0XA0
EEx [ia] IIC
110 mA
13.5 V DC
45.45 kBit/s**
Siemens DP/PA-coupler
6ES7157-0AD82-0XA0
EEx [ia] IIC
110 mA
13.5 V DC
45.45 kBit/s**
Table 4-3: Segment couplers on the market * in coinnection with gateway KLD2-GT-DP.xPA or KLD2-GT-DPR.xPA ** in connection with 6ES7157-0AA8x-0XA0 as DP/PA link, rates from 9.6 kBit/s up to 12 MBit/s are supported.
4.2.2
Link
A link comprises an intelligent interface and one or more segment couplers, whereby the couplers may exhibit different types of protection. Normally, a range of transmission rates are supported on the PROFIBUS DP side. The transmission rate for PROFIBUS PA is fixed at 31.25 kbit/s. Links differ from pure segment couplers by the fact that they are PROFIBUS DP slaves on one side and PROFIBUS PA masters on the other. There is no direct communication between the PROFIBUS DP master and the PROFIBUS PA slaves, i.e. the link is not transparent. Futher information is to be found in the sections on addressing and cycle times.
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4.3
4 PROFIBUS PA Basics
Topology
The field devices on the PROFIBUS PA segment communicate with a master on the PROFIBUS DP system. The bus is designed according to the rules for PROFIBUS DP up to the segment coupler or link, see Chapter 3.2. Within the PROFIBUS PA segment, practically all topologies are permissible, see Fig. 4-3, below. Termination at JB possible if spurs do not exceed 30 m
Fig. 4-3: Bus topologies (A:Tree, B:Bus, C:Bus + Tree, D:Bus + Tree + extension), PNK: process near component, SiK: Signal coupler, SG: Power supply, T: Terminator, JB: Junction box, R: Repeater, 1...n: Field devices, Sk: Segment coupler
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Cable type
PROFIBUS planning and commissioning
The fieldbus comprises two-core cable. According to IEC 61158-2 (MBP), four different cable types (A, B, C, D) can be used, only two of which (cable types A and B) are shielded. • Cable types A or B are recommended for new installations. Their cable shielding guarantee adequate protection from electromagnetic interference and thus the most reliable data transfer. On multi-pair cables (Type B), it is permissible to operate multiple fieldbuses (with the same degree of protection) on one cable. No other circuits are permissible in the same cable. • Practical experience has shown that cable types C and D should not be avoided where possible since the lack of shielding means that electromagnetic interference characteristics generally do not meet the requirements described in the standard. Table 4-4 lists the technical data of the four cable types as taken from the informative annex to the standard (i.e. this has not actually been specified.) The electrical data determine important characteristics of the design of the fieldbus, such as distances bridged, number of participants, electromagnetic compatibility, etc. Cable type A
Cable type B
Cable type C
Cable type D
Cable construction
twisted pair, shielded
one or more twisted pairs, common shielded
one or more twisted pairs, unshielded
one or more untwisted pairs, unshielded
Core cross-section
0.8 mm2 AWG 18
0.32 mm2 AWG 22
0.13 mm2 AWG 26
1.23 mm2 AWG 16
Loop resistance (DC)
44 Ω/km
112 Ω/km
254 Ω/km
40 Ω/km
Characteristic impedance at 31.25 kHz
100 Ω ±20 %
100 Ω ±30 %
—
—
Attenuation constant at 39 kHz
3 dB/km
5 dB/km
8 dB/km
8 dB/km
Capacitive unsymmetry
2 nF/km
2 nF/km
—
—
Envelope delay distortion (7.9...39 kHz)
1.7 µs/km
—
—
—
Degree of coverage of shielding
90 %
—
—
—
Max. recommended bus length (including spurs)
1900 m
1200 m
400 m
200 m
Table 4-4: Cable types according IEC 61158-2, Annex C
Intrinisic safety
Cable for intrinsically safe applications as per the FISCO model must also satisfy the following additional requirements: EEx ia/ib IIC
EEx ib IIB
Loop resistance (DC)
15...150 Ω/km
15...150 Ω/km
Specific inductance
0.4...1 mH/km
0.4...1 mH/km
Specific capacitance
80...200 nF/km
80...200 nF/km
Max. spur length
≤ 30 m
≤ 30 m
Max. bus length
≤ 1000 m
≤ 1900 m
Table 4-5: Safety limits for the bus cable according FISCO
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Cable manufacturers
4 PROFIBUS PA Basics
Table 4-6 list examples for Type A PROFIBUS-PA cable available from various manufacturers. Manufacturer
Order No.
Application
Specific resistance
Turck
Cable 483-*M
Standard
≤ 44 Ω/km
Turck
Cable 483B-*M
EEx ia/ib IIC
≤ 44 Ω/km
Siemens
6XV1830-5FH10
Standard
≤ 44 Ω/km
Siemens
6XV1830-5EH10
EEx ia/ib IIC
≤ 44 Ω/km
Lapp
2170235
Standard
≤ 44 Ω/km
Lapp
2170234
EEx ia/ib IIC
≤ 44 Ω/km
Table 4-6: PROFIBUS PA cable
Maximum overall cable length
The maximum network length depends on the type of ignition protection and the cable specifications. The overall cable length is made up of the length of the main cable and the length of all spurs that are longer than 1 m. Cable type A
Cable type B
Cable type C
Cable type D
1900 m
1200 m
400 m
200 m
Table 4-7: Maximum permissible overall cable length depending upon the cable type used
!
Maximum spur length
Note! • In FISCO systems with type of protection EEx ia, the maximum line length 1000 m • If repeaters are used, the maximum permissible cable length is [length in table x (N+1)], where N is the number of repeaters. • A maximum of four repeaters are permitted between station and master. The line between distribution box and field device is described as a spur. In the case of non ex-rated applications the max. length of a spur depends on the number of spurslonger than 1 m: Number of spurs
1...12
13...14
15...18
19...24
25...32
Max. length per spur
120 m
90 m
60 m
30 m
1m
Table 4-8: Maximum length of a spur depending on the number of spurs
!
Note! • In FISCO systems with type of protection EEx ia, the max. length per spur is 30 m.
Number of field devices
As far as the specification is concerned, a maximum of: • 32 stations per segment in safe areas • 10 stations in an explosive hazardous arrea (EEx ia IIC) are possible. The actual number of stations is dependent on several factors, however, and must be determined during project planning.
Bus termination
The start and end of each fieldbus segment must be terminated with a bus terminator. The terminator may be a separate component or be integrated into a bus component.
!
Endress+Hauser
Note! • If the segment is in an explosion hazardous area, the terminators must be certified to the FISCO standard. • In the case of a branched bus segment, the device furthest from the segment coupler represents the end of the bus. • If the fieldbus is extended with a repeater then the extension must also be terminated at both ends.
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4.4
Bus access method
PROFIBUS PA uses the central master/slave method to regulate bus access. The process near component, e.g. a PLC, is a Class 1 master that is installed in the PROFIBUS DP system. The field devices are configured from a PROFIBUS PA Class 2 master, e.g. FieldCare. The field devices on the PROFIBUS PA segment are the slaves.
4.4.1
Segment coupler
Segment couplers are transparent as far as the PROFIBUS DP master is concerned, so that they are not mapped in the PLC. They simply convert the signals and power the PROFIBUS PA segment. The do not need to be configured nor are they assigned an address. The field devices in the PROFIBUS PA segment are each assigned a PROFIBUS DP address and behave as PROFIBUS DP slaves. A slave may be assigned to only one Class 1 master. A master communicates directly with its slaves: • A Class 1 master, e.g. the PLC, uses the cyclic polling services to fetch the data provided by the field devices. • A Class 2 master, e.g. FieldCare, transmits and receives field device data by using the acyclic services.
e.g. FieldCare Class 2 master
PLC Class 1 master
PROFIBUS DP cyclic data exchange Segment coupler
acyclic data exchange
PROFIBUS PA
PROFIBUS PA-slaves
Fig. 0.1
Segment coupler SK1 from Pepperl+Fuchs
Data exchange via segment coupler
If the SK1 segment coupler is used, the transfer rate for the PROFIBUS DP is fixed at 93.75 kBd. In this case, if type A cable is used for the PROFIBUS DP the PROFIBUS DP segment can be up to a length of 1200 m. The length of the PROFIBUS PA segment depends on: • • • •
whether the PROFIBUS PA segment in question is intrinsically safe or not. how many PROFIBUS PA stations are connected to the segment. how high is the current consumption of the individual PA slaves. how the PA slaves are distributed on the PROFIBUS PA segment.
The SK1 segment coupler works transparently. This means that PROFIBUS DP masters have direct access to every PROFIBUS PA slave. Addresses that have been assigned on a PROFIBUS PA segment are also occupied on the PROFIBUS DP.
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4.4.2
4 PROFIBUS PA Basics
Gateway-type segment coupler
This type of segment coupler allows several segments to be connected to one central coupler unit, whilst retaining the transparency of the unit. For the user, however, it operates in exactly the same manner as the normal segment coupler, see Fig. 4-5.
e.g. FieldCare Class 2 master PLC Class 1 master
PROFIBUS DP
acyclic data exchange
SK 2
cyclic data exchange
Gateway Segment coupler 1 ... max. 5
PROFIBUS PA
PROFIBUS PA-slaves
PROFIBUS PA-slaves
Fig. 4-4: Bus access using a Pepperl+Fuchs SK2 segment coupler
Segment coupler SK2 from Pepperl+Fuchs
The SK2 segment coupler is a modular unit comprising power pack, gateway with up to four channels and up to 20 power links. The power links supply (intrinsically safe) power to their segments, whilst the gateway couples the PROFIBUS PA devices to the PROFIBUS-DP network. A maximum of five power links per channel is allowed. The SKs has the following properties: • • • •
No restriction on PROFIBUS PA data volume (244 Byte I/O per slave possible) Support of PROFIBUS DP transfer rates (45,45 kBd... 12 MBd) No addressing of the segment coupler, either PROFIBUS DP or PROFIBUS PA Direct access for the PROFIBUS DP master to the PROFIBUS PA slave (transparency).
The major difference to a standard segment coupler is the variable transmission rate on the DP side. This allows better cycle times to be attained in mixed DP/PA systems.
!
Endress+Hauser
Note! • When a SK2 coupler is used in a PROFIBUS network, the GSD files of the PROFIBUS PA slaves to be connected to it must be converted using a special program supplied by Pepperl+Fuchs. • Despite the conversion, the PNO certificates for these devices still retain their validity. • No PROFIBUS PA slave may be assigned the address 1.
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4.4.3
Links
In contrast to a segment coupler, a link is recognised by the PROFIBUS DP master and is a participant in the PROFIBUS DP system. It is assigned a PROFIBUS DP address and thus becomes opaque to the master. The field devices on the PROFIBUS PA side can no longer be directly polled using the cyclic services. Instead, the link collects the device data in a buffer, which can be read cyclically by a Class 1 master. Hence a link must be mapped in the PLC. On the PROFIBUS PA side, the link acts as the PA master. It polls the field device data cyclically and stores them in a buffer. Every field device is assigned a PROFIBUS PA address that is unique for the link, bit which may be used in a segment connected to another link. When the link is accessed by a Class 2 master with the acyclic services it is quasi-transparent. The desired field device can be accessed by specifying the link address (DP address) and the device address (PA address).
PLC Class 1 master
e.g. FieldCare Class 2 master
PROFIBUS DP
Cyclic data exchange with Class 1 master using the master-slave method
Acyclic data exchange with Class 2 master using the master-slave method
Link
PROFIBUS PA-slaves
PROFIBUS PA-slaves
Fig. 4-5: Data exchange via a link
Siemens DP-/PA link
The Siemens DP/PA link acts as described above. It supports PROFIBUS DP transmission rates from 9.6 kBit/s up to 12MBit/s. As indicated, the DP/PA link is not transparent and must be planned in the PLC or control system by means of a GSD file. Among other things, all the cyclic I/O data of the connected slaves must be entered into this file. In order to facilitate the generation of a project specific GSD file for the link, Siemens supplies a special software application. The link is limited in the amount of PROFIBUS PA data it can transmit. The total amount of cyclic I/O data permitted, i.e. the accumulated total from all PROFIBUS PA devices connected to the link, is 244 bytes for input and 244 bytes for output data.
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4.5 Data transmission
4 PROFIBUS PA Basics
Network Configuration
Data exchange on the PROFIBUS PA segment is handled by the IEC 61158-2 interface. The cyclic and acyclic polling services are used to transmit data. Since the PROFIBUS PA standard offers the possibility of interconnecting devices from different vendors, a profile set has been defined that contains standardised device parameters and functions: • Mandatory parameters: Every device must provide these parameters. These are parameters, with which the basic parameters of the device can be read or configured. • Application parameters: These are optional parameters. These parameters allow a calibration and, e.g., additional functions such as a linearisation to be performed. In view of the fact that these functions are dependent upon the measured variable, there are several profile sets, e.g. for level, pressure, flow etc.. The parameters can be accessed acyclically and require a Class 2 master, e.g. FieldCare, if they are to be read or modified. Cyclic data exchanged is handled by standard telegrams. The permissible telegram length depends upon the master used: according PROFIBUS PA-standard, 244 bytes for inputs and 244 bytes for outputs. • For PROFIBUS PA devices, analogue measured values and status are transmitted in 5 bytes. If a device offers more values, more bytes may be transmitted, see Chapter 3.4. • In the case of the level limit swich Liquiphant M/S, the limit signals are transmitted in 2 bytes per channel. Byte 1 contains the signal condition, byte 2 the status.
GSD (device database file)
In order to integrate the field devices into the bus system, the PROFIBUS DP system requires a description of the device parameters such as output data, input data, data format, data length and the transmission rates supported. These data are contained in the GSD device database file, which is required by the PROFIBUS DP master during the commissioning of the communication system. In addition, device bit maps are required, which appear as icons in the network tree. Further information on device database files is to be found in Chapter 7.2.
Bus address
A pre-requisite for communication on the bus is the correct addressing of the participants. Every device on the PROFIBUS PA segment is assigned a unique address between 0 and 125. The addressing is dependent upon the type of DP-/PA-interface used (segment coupler or link) and is set by DIP switches, via on-site operating elements or by software. The addressing procedure is described in detail in Chapter 5.5.
Transmission rate
The transmission rate on a PROFIBUS PA segment is fixed at 31.25 kbit/s. The transmission rate on PROFIBUS DP is dependent upon the application and the type of DP-/PA-interface used (segment coupler or link).
Bus parameters
In addition to the transmission rate, all active participants on the bus must operate with the same bus parameters. For the operating and display program Commuwin II, the bus parameters can be set by using the DPV1-DDE server (submenu Parameter Settings). For FieldCare the bus parameters can be set by using the corresponding Communication-DTM.
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4.6
FISCO
To render the proof of Intrinsic Safety as simple as possible, the so-called FISCO model was developed. FISCO stands for Fieldbus Intrinsically Safe COncept. The German PTB (Federal Technical Institute) developed the FISCO model and has published details in Report PTB-W-53 "Examination of intrinsic safety for fieldbus systems“. This model is based on the following prerequisites: 1. To transmit power and data, the bus system uses the physical configuration defined by IEC 61158-2. This is the case for PROFIBUS PA. 2. Only one active source is permitted on a bus segment (in this case the segment coupler). All other components work as passive current sinks. 3. The basic current consumption of a bus station is at least 10 mA. 4. It must be ensured for each bus station that – Ui > Uo of the segment coupler/power link – Ii > Io of the segment coupler/power link – Pi > Po of the segment coupler/power link 5. Each bus station must fulfill the following requirement: – Ci < 5 nFLi – Li < 10 µH– 6. The permissible line length for EEx ia IIC applications is 1000 m. 7. The permissible spur length for Ex applications is 30 m per spur. The definition of the spur must be observed in this connection (= lines longer than 1 m). 8. The bus cable used must conform to the following cable parameters: – Specific resistance: 15 Ω/km < R' < 150 Ω/km – Specific inductance: 0.4 mH/Km < L' < 1 mH/km – Specific capacitance: 80 nF/km < C' < 200 nF/km (including the shield) Taking the shield into consideration, the specific capacitance is calculated as follows: – C' = C'conductor/conductor + 0.5 * C'conductor/shield, if the bus line is potential free or – C' = C'shield/shield + C'conductor/shield, if the shield is connected with a terminal of the segment coupler/power link. 9. The bus segment must be terminated on both ends with a fieldbus terminator. According to the FISCO model the terminal bus resistance must conform to the following limits: – 90 Ω < R < 100 Ω – 0 µF < C < 2.2 µF On condition that the points 1 up to 9 are all satisfied, the proof of intrinsic safety has been provided by means of the FISCO model. Points 1, 3 and 5 are automatically satisfied if a product is certified in accordance with the FISCO model. More information on the planning of PROFIBUS PA systems is to be found in Chapter 5.
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4.7
4 PROFIBUS PA Basics
Fieldbus multi-drop barriers
When a PROFIBUS PA segment is operated according to FISCO, the segment coupler ensures intrinsic safety by limiting the current available to the bus. This results in the number of devices per segment being limited to a maximum of 10. If the application demands a large number of intrinsically safe devices, a correspondingly large number of Exi segment couplers are required. Multi-drop barriers provide an alternative and more economic solution to such applications.
0 - 10 bar
0 - 10 bar
Exe power supply and conditioner
T
MULTIDROP BARRIER Ex e/Ex i
T
MULTIDROP BARRIER Ex e/Ex i
Coupler
Fig. 4-6: Use of multi-barriers in explosion-hazardous areas - barriers mounted in Zone 1.
The multi-drop barriers are connected to a non-intrinsically safe PROFIBUS segment. In order that the barriers can be mounted and operated in Zone 1, however, the segment is executed to "enhanced safety, Exe" standards. Similarly, the terminals of the barriers are executed to Exe. Multi-drop barriers have several intrinsically safe outputs (usually four) that conform to the FISCO model. The PA slaves connected must be intrinsically safe and certified as FISCO devices. Any externally powered devices must have Exe or Exd power supplies and appropriate connection compartment certification. The barriers offer additional protection of the PROFIBUS PA trunk cable, since they have short-circuit protection. In view of the fact that the trunk cable does not have to be intrinsically safe, the full power of a standard non-Ex coupler can be used on the segment, typically 400 mA, see Chapter 5.2. This means that up to 32 devices can be operated per segment, should this be required.
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PROFIBUS planning and commissioning
5
PROFIBUS PA Planning
Various aspects must be taken into consideration when a PROFIBUS-PA segment is planned. Since the importance of each aspect varies from system to system, it is recommended that the following sections are worked through one after the other. If at some point it becomes obvious that a concept cannot be realised, then start the whole procedure again from the beginning with a modified concept. The chapter is structured as follows: • • • • • • •
Selection of the segment coupler Cable type and length Current consumption Voltage at last device Example calculations for bus design Data quantity Addressing and cycle times
5.1
Selection of the segment coupler
The first step in planning a PROFIBUS-PA system is the selection of the segment coupler according where the segment is to be operated, see also Chapter 2.3.2. Table 5-1 summerises these:. Zone/Explosion group
Segment coupler
Remarks
Zone 0
[EEx ia] IIx
Devices that are in installed in Zone 0 must be operated in a segment with type of protection "EEx ia". All circuits connected to this segment must be certified for type of protection "EEx ia".
Zone 1
[EEx ia] IIx [EEx ib] IIx
Devices that are in installed in Zone 1 must be operated in a segment with type of protection "EEx ia" or "EEx ib". All circuits connected to this segment must be certified for type of protection "EEx ia" or "EEx ib".
Explosion group IIC
IIC [EEx ia] IIC
If measurements are made in a medium of explosion group IIC, the devices concerned as well as the segment coupler must be certified for explosion group IIC.
Explosion group IIB
[EEx ia] IIC [EEx ib] IIB
For media of explosion group IIB, both the devices and the segment coupler can be certified for both group IIC or IIB.
Non-Ex
Non-Ex
Devices that are operated on a non-Ex segment may not be installed in an explosion hazardous area.
Table 5-1: Selection of the segment coupler according to the type of protection and the explosion group of the measured media.
Table 4-3 in Section 4.2.1 lists the couplers currently on the market.
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Endress+Hauser
PROFIBUS planning and commissioning
5.2
5 PROFIBUS PA Planning
Cable type and length
The bus length is dependent upon the type of protection of the segment and the specification of the cable. In order that the basic requirements for transmission on the IEC 61158-2 (MBP) physical layer are fulfilled and that the inductance and capacitance of the cable can be neglected, the bus length and loop resistance are limited. Table 5-2 lists data from PROFIBUS specifications. Power supply
Type A
Type B
Type C
Application
EEx [ia/ib] IIC
EEx [ib] IIB
Non-Ex
Supply voltage*
13.5 V
13.5 V
24 V
Max. power*
1.8 Ω
4.2 Ω
9.1 Ω
Max. current consumption*
≤ 110 mA
≤ 280 mA
≤ 400 mA
Max. loop resistance
≤ 40W
≤ 16W
≤ 39 W
Max. bus segment length
1000 m (EEx ia)
1900 m
1900 m
Max. spur length
30 m
30 m
see Table 5-3
*see also the technical data supplied by the manufacturer Table 5-2: Standardised power supplies with max. loop resistance and bus length for various applications
Bus length
The bus length is the sum of the length of the trunk cable plus all spurs. A spur is any cable connecting to the trunk line that is over 1 metre in length. If a repeater is used, then the max. permissible length is doubled.
Spurs
The spurs are subject to the following limitations: • Spurs longer than 30 m are not permissible in explosion hazardous areas. • For non-hazardous applications, the maximum length of a spur is dependent upon the number of field devices, see Table 5-3. • Spurs which are shorter than 1 m are treated as connection boxes and are not included in the calculation of the total bus length, provided that they do not together exceed 8 m for a 400 m bus or 2 % of the total length for a longer bus. No. of field devices
25-32
19-24
15-18
13-14
1-12
Spur length
≤1m
30 m
60 m
90 m
120 m
Table 5-3: Max. spur length for non-hazardous applications
Max. cable length (worst case)
The maximum cable length for a particular cable resistance is calculated as follows, whereby the limits in Table 4.4. must be observed: Max. cable length (km) = max. loop resistance of the segment coupler (Table 5-2) specific resistivity of the cable Ω/km If not given, the loop resistance is (Ω/km) = 2 x (1000 ρ/A) whereby ρ = specific resistivity Ω mm2/m und A = core cross-section mm2. Table 4-6 in Chapter 4.3 lists examples for the PROFIBUS-PA cable available from various manufacturers.
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5 PROFIBUS PA Planning
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5.3
Current consumption
The primary factors in determining the number of devices on a segment are the current supplied by the segment coupler and the current consumption of the field devices. For this reason, the current consumption must be calculated for every segment. As a rule of thumb for general planning: • Max. 32 devices per segment are permissible in non-hazardous areas (A repeater allows more devices on the segment). • Max. 10 devices are permissible in hazardous areas of category ia. For the calculation, the current supplied by the segment coupler IS, the basic current of every device IB and the fault current of every device IFDE must be known. From the electrical point of view, a segment is permissible when: IS ≥ ISEG ISEG = ΣIB + max. IFDE
whereby
Table 5-4 lists the basic current, the fault current and other specifications of Endress+Hauser devices. The following examples illustrate how the calculation should be made. Empty forms can be found in Appendix A. Device current consumption
52
Type
IB (mA)
IFDE (mA)
Supply current
Ui (V)
Ii (mA)
Pi (W)
Operating instructions
Safety instructions
Cerabar S
11
0
from bus
17.5
500
5.5
BA222P/00/en
XA096P, XA097P
Cerabar S
11
0
from bus
17.5
280
4.9
BA168P/00/en
XA004P
Deltabar S
11
0
from bus
17.5
280
4.9
BA167P/00/en
XA003P
Deltapilot S
11
0
from bus
17.5
280
4.9
BA164P/00/en
XA007F
FXA164
29
5
from bus
15
215
1.93
---
XA093F, ATEX 2150
Levelflex M
11
0
from bus
17.5
500
5.5
BA243F/00/en
KEMA 02, ATEX 1109
Liquiphant M
11
0
from bus
30
500
5.5
BA141F/00/en
ATEX 5172X
Liquisys M
11
0
local
non EX
non EX
non EX
BA209C/07/en
---
Micropilot II
12
0
from bus
17.5
280
4.9
BA176F/00/en, BA202F/00/en
XA013F, XA018F, XA021F
Micropilot M
13
0
from bus
17.5
500
5.5
BA225F/00/en, BA226F/00/en
XA102F, XA106F
Multicap
14
0
from bus
17.5
500
5.5
BA261F/00/en
---
Mycom CPM152
11
0
local
17.5
280
4.9
BA143C/07/en
XA143C, 130849
Mycom CPM153
11
0
local
17.5
280
4.9
BA298C/07/en
---
Mypro CXX431
11
0
from bus
17.5
280
4.9
BA198C/07/en
XA173C, 130849
Promag 33
12
0
local
30
500
5.5
BA029D/06/en
XA009D
Promag 35
12
0
local
non EX
non EX
non EX
BA029D/06/en
---
Promag 50
11
0
local
30
500
5.5
BA055D/06/en
ATEX E003U
Promag 53
11
0
local
30
500
5.5
BA053D/06/en
ATEX E003U
Endress+Hauser
PROFIBUS planning and commissioning
5 PROFIBUS PA Planning
Type
IB (mA)
IFDE (mA)
Supply current
Ui (V)
Ii (mA)
Pi (W)
Operating instructions
Safety instructions
Promass 63
12
0
local
30
500
5.5
BA033D/06/en
XA003D
Promass 80
11
0
local
non EX
non EX
non EX
BA072D/06/en
---
Promass 83
11
0
local
30
500
5.5
BA063D/06/en
ATEX E074X
Prosonic Flow 93
11
0
local
30
500
5.5
BA076D/06/en
ATEX E064X
Prosonic M
12
0
from bus
17.5
500
5.5
BA238F/00/en
XA175F-A
Prosonic T
13
0
from bus
17.5
280
4.9
BA166F/00/en
XA008F
Prosonic T FMU232
17
0
from bus
17.5
280
4.9
BA166F/00/en
XA008F, XA035F
Prowirl 72
15
0
from bus
17.5
500
5.5
BA085D/06/en
XA071DA3
Prowirl 77
12
0
from bus
17.5
280
4.9
BA037D/06/en
EX038D
RID261
11
0
from bus
15
---
---
BA098R06/en
XA002R, E062
Smartec S
11
0
local
non EX
non EX
non EX
BA213C/07/en
---
TMD834
13
0
from bus
17.5
280
4.9
BA090R06/en
EX-98.D.089
TMT184
11
0
from bus
17.5
500
5.5
BA115R06/en
XA008R
Table 5-4: PROFIBUS PA data of Endress+Hauser devices
Endress+Hauser
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5 PROFIBUS PA Planning
PROFIBUS planning and commissioning
5.4
Voltage at last device
The resistance of the cable causes a voltage drop on the segment that is greatest at the device farthest from the segment coupler. It must be checked whether an operating voltage of 9 V (for FEB 24 P in Zone 0 9.6 V) is present at this device. There are two ways of doing this: • Worst case calculation: if the resulting voltage is over 9V, then the segment will work in all cases • Accurate calculation: this calculation takes into account the actual physical distribution of the devices and should be used if the worst case calculation gives a voltage less than 9V
5.4.1
Worst case calculation
The worst case assumes that all devices are located at the end of the bus. The equivalent curcuit diagram is shown in Fig. 5.1 ISEG
RL I1
Segment coupler
UL US
In I2
>9V
Fig. 5-1: Voltage calculation and line length (Example 1)
Voltage
The length of the bus is known, the voltage at the last device is to be calculated. Ohm's law is used: UB = US – (ISEG x RSEG) whereby: UB = Voltage at last device US = Output voltage of the segment coupler (manufacturer's data) ISEG = Current consumed on the segment (ΣIB + max. IFDE, see Section 4.3) RSEG = Cable resistance = bus length x specific resistance
Bus length
The bus length is to be calculated from given conditions on the bus. A PROFIBUS PA slave requires at least 9 V to function properly (for FEB 24 P in Zone 0 9.6 V). The following applies to the maximum voltage drop over the bus: ULmax = US - 9 V where
ULmax = the maximum permissible voltage drop over the bus US = Output voltage of the segment coupler (manufacturer's data)
The corresponding line length in metres L = 1000 x ULmax / [ISEG x ρ] where
54
metres
ISEG = Current consumed on the segment in amps (ΣIB + max. IFDE, see Section 4.3) ρ = specific resistivity of the bus cable in Ω/km
Endress+Hauser
PROFIBUS planning and commissioning
5.4.2
5 PROFIBUS PA Planning
Accurate calculation
This calculation takes into account the actual distribution of the devices on the bus. The equivalent circuit is shown in Fig. 5-2,where: RLx = line resistance of line segment x in Ω and In = current consumption of PA station n in amps
L2 L2 L1 RL1
RL2
i1
Segment coupler
In
I2
US >9V
Fig. 5-2: Voltage calculation and line length (Example 2)
Each station causes a voltage drop on the length segment through which its power supply current flows. For the first station, this would be: URL1 = = where
I1 x RL1 I1 x L1 x ρ ;
ρ = the specific resistance bus cable in Ω/km L1 = length of line segment 1 in km, measured from the terminals of the coupler
For the second station, the following applies: URL2 = =
I2 x (RL1 + RL2) I2 x L2 x ρ
In general, the voltage drop over the entire bus segment URL is: n URL = ρ x Σ ¨[Ix x Lx] x=1 The segment is in order when: URL = US - 9 V where
Us is the supply voltage
If the condition described above is not fulfilled, • the bus has be shortened or • a cable with reduced specific resistivity has to be used or • the number of devices on the segment must be reduced.
Endress+Hauser
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5 PROFIBUS PA Planning
PROFIBUS planning and commissioning
5.5
Calculation examples for bus design
5.5.1
Example 1: Non-hazardous application
Calculation example for a PROFIBUS PA segment in a non-hazardous area with the architecture shown in Fig. 4.3. Used components: • Segment coupler non-hazardous area: Siemens, Is = 400 mA, Us = 19 V. • Cable: Lapp, specific resistance of cable = 44 Ω/km
Segment coupler, non-hazardous Us = 19 V IS = 400 mA
Trunk cable 40 m
20 m
20 m
15 m
5m
7m
7m
20 m
20 m
15 m
5m
7m
20 m
Spur
UB = 17.81 V
Fig. 5-3: Example 1: Bus installed in non-hazardous area
Cable length (worst case)
Max. loop resistance, non-hazardous area (see Table 5-2)
39 Ω
Specific resistance of cable
44 Ω/km
Max. length (m)= 1000 x (loop resistance/specific resistance) 1000 x (39 Ω/44 Ω) =
886 m
Length of trunk cable
60 m
Total length of spurs
141 m
Total length of cable (= trunk cable + spurs) LSEG
201 m
Total length of cable LSEG 201 m < Max. length 886 m
OK!
Table 5-5: Cable length (worst case) non-hazardous area
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Endress+Hauser
PROFIBUS planning and commissioning
Current consumption
5 PROFIBUS PA Planning
No.
Device
Manufacturer
Tag
Basic current
Fault current
1
Promass 83
Endress+Hauser
FIC122
11 mA
0 mA
2
Positioner
––––
FV121
10 mA
0 mA
3
Levelflex M
Endress+Hauser
LIC124
11 mA
0 mA
4
TMT 184
Endress+Hauser
TIC123
11 mA
0 mA
5
Promass 83
Endress+Hauser
FIC126
11 mA
0 mA
6
Positioner
––––
FV125
10 mA
6 mA
7
Promass 83
Endress+Hauser
FIC222
11 mA
0 mA
8
Positioner
––––
FV221
10 mA
0mA
9
Levelflex M
Endress+Hauser
LIC224
11 mA
0 mA
10
TMT 184
Endress+Hauser
TIC223
11 mA
0 mA
11
Promass 83
Endress+Hauser
FV226
11 mA
0 mA
12
Positioner
––––
VIC225
11 mA
4 mA
Max. fault current (max. IFDE)
6mA
Current consurption ISEG = ΣIB + max. IFDE
135 mA
Output current of segment coupler Is
400 mA
Is ≥ ΣIB + max. IFDE ?
Yes
OK!
Table 5-6: Current consumption (non-hazardous area)
Voltage at last device
Output voltage of segment coupler US (manufacturer’s data) Specific resistance of cable RK
44 Ω/km
Total length of cable LSEG
201 m
Resistance of cable RSEG = LSEG x RK
8.844 Ω
Current consumption of segment ISEG
135 mA
19.00 V
Voltage drop UA = ISEG x RSEG
1.19 V
Voltage at last device UB = US - UA
17.8 V
≥9V
OK!
Table 5-7: Voltage at last device (non-hazardous area)
Conclusion
Result of the calculations: • Cable length: OK • Current consumption: OK • Voltage at last device: OK From the point of view of the architecture, the segment in Example 1 can be operated with a standard segment coupler with an output current of 400 mA.
Endress+Hauser
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5 PROFIBUS PA Planning
PROFIBUS planning and commissioning
5.5.2
Example 2: EEx ia application
In Examples 2 and 3, the PROFIBUS PA segment is to operate in an explosion hazardous area. In accordance with the FISCO model, the devices are operated on two separate segments with type of protection EEx ia for Zone 0 and EEx ib for Zone 1. Calculations are made for both segments. Specimen calculation for a bus operating in a hazardous area Zone 0 with the architecture shown in Fig. 5-4. • Segment coupler [EEx ia] IIC: P+F, Is = 100 mA, Us = 13 V. • Cable: Siemens, specific resistance of cable = 44 Ω/km, max. bus length = 1000 m. Segment coupler [EEx ia] IIC IS = 100 mA US = 13 V
EEx ib EEx ia
Spur
15 m
15 m
5m
5m
Trunk cable 50 m
Fig. 5-4: Example 2: Calculation of the segment EEx ia, Bus installed with routing to Zone 0 (EEx ia) and Zone 1 (EEx ib)
Cable length (worst case)
Max. loop resistance, EEx (see Table 4.3)
40 Ω
Specific resistance of the cable
44 Ω/km
Max. length (m)= 1000 x (loop resistance/specific resistance) 1000 x (40 Ω/44 Ω) =
909 m
Length of trunk cable
50 m
Total length of spurs
40 m
Total length of cable (= trunk cable + surs) LSEG
90 m
Total length of cable LSEG 90 m < Max. length 909 m
OK!
Table 5-8: Cable length (worst case) EEx ia area
58
Endress+Hauser
PROFIBUS planning and commissioning
Current consumption
5 PROFIBUS PA Planning
Nr.
Device
Manufacturer
Tag
Basic current
Fault current
3
Deltapilot S
Endress+Hauser
LIC124
11 mA
0 mA
4
TMT 184
Endress+Hauser
TIC123
11 mA
0 mA
9
Deltapilot S
Endress+Hauser
LIC224
11 mA
0 mA
10
TMT 184
Endress+Hauser
TIC223
11 mA
0 mA
Ma. fault current (max. IFDE)
0 mA
Current consumption ISEG = ΣIB + max. IFDE
44 mA
Output current of segment coupler Is
100 mA
Is ≥ ΣIB + max. IFDE ?
Yes
OK!
Table 5-9: Current consumption (EEx ia area)
Voltage at last device
Output voltage of segment coupler US (manufacturer’s data) Specific resistance of cable RK
44 Ω/km
Total length of cable LSEG
90 m
Resistance of cable RSEG = LSEG x RK
3.96 Ω
Current consumption of segment ISEG
44 mA
13.00 V
Voltage drop UA = ISEG x RSEG
0.17 V
Voltage at last device UB = US - UA
12.83 V
≥ 9 V?∗
OK!
*the operating voltage for the FEB 24 P in Zone 0 is 9.6 V Table 5-10: Voltage at last device (EEx ia area)
Conclusion
Result of the calculations: • Cable length: OK • Current consumption: OK • Voltage at last device: OK From the point of view of the architecture, the segment in Example 2 can be operated with an EEx ia segment coupler with an output current of 100 mA.
Endress+Hauser
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5 PROFIBUS PA Planning
PROFIBUS planning and commissioning
5.5.3
Example 3: EEx ib application
Specimen calculation for a bus operating in a hazardous area Zone 1 with the architecture shown in Fig. 5-5. • Segment coupler [EEx ia/ib] IIC: P+F, Is = 100 mA, • Us = 13 V. Cable: Siemens, specific resistance of cable = 44 Ω/km Segment coupler [Ex ia/ib] IIC IS = 100 mA US = 13 V
Trunk cable 60 m
UB = 12.31 V
EEx ib
7m
20 m
20 m
20 m
20 m
Spur
7m
7m
7m
EEx ia
Fig. 5-5: Example 3: Calculation of the segment EEx ib, Bus installed with routing to Zone 0 (EEx ib) and Zone 1 (EEx ia)
Cable length (worst case)
Max. loop resistance, EEx (siehe Tabelle 4.3)
16 Ω
Specific resistance of cable
44 Ω/km
Max. length (m)= 1000 x (loop resistance/specific resistance) 1000 x (40 Ω/44 Ω) =
363 m
Length of trunk cable
60 m
Total length of spurs
108 m
Total length of cable (= trunk cable + spurs) LSEG
168 m
Total length of cable LSEG 168 m < Max. lenght 363 m
OK!
Table 5-11: Cable length (worst case) EEx ib area
60
Endress+Hauser
PROFIBUS planning and commissioning
Current consumption
5 PROFIBUS PA Planning
No.
Device
Manufacturer
Tag
Basic current
Fault current
1
Promass 83
Endress+Hauser
FIC122
11 mA
0 mA
2
Positioner
––––
FV121
13 mA
0 mA
5
Promass 83
Endress+Hauser
FIC126
11 mA
0 mA
6
Positioner
––––
FV125
13 mA
6 mA
7
Promass 83
Endress+Hauser
FIC222
11 mA
0 mA
8
Positioner
––––
FV221
13 mA
0 mA
11
Promass 83
Endress+Hauser
FIC226
11 mA
0 mA
12
Positioner
––––
FV225
13 mA
6 mA
Max. fault current (max. IFDE)
6 mA
Current consumption ISEG = ΣIB + max. IFDE
102 mA
Output current of segment coupler Is (EEx ia IIC)
100 mA
Is ≥ ΣIB + max. IFDE ?
no
Output current of segment coupler Is (EEx ia IIB)
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