Configuring and Testing Smart Field Devices

 

Contents

Module 1 Fundamentals of process measurement.

OBJECTIVES……………………………............................................................................... 7

1.0 INTRODUCTION ........................................................................................................ 10

1.1 PRESSURE MEASUREMENT ................................................................................... 10

1.1.1 General Theory ........................................................................................................ 10

1.1.2 Pressure Scales........................................................................................................ 10

1.1.3 Pressure Measurement ............................................................................................ 10

1.1.4 Common Pressure Detectors.................................................................................... 12

1.1.5 Differential Pressure Transmitters ............................................................................15

1.1.6 Strain Gauges.............................................  .............................................................16

1.1.7 Capacitance Capsule ....................................  ..........................................................17

1.1.8 Impact of Operating Environment ……………………….............................................18

1.1.9 Failures and Abnormalities .......................................................................................19

1.2 FLOW MEASUREMENT...............................................................................................20

1.2.1 Flow Detectors ..........................................................................................................20

1.2.2 Square Root Extractor...............................................................................................28

1.2.3 Density Compensating Flow Detectors .....................................................................32

1.2.4 Flow Measurement Errors..........................................................................................34

1.3 LEVEL MEASUREMENT .............................................................................................35

1.3.1 Level Measurement Basics .......................................................................................35

1.3.2 Three Valve Manifold................................................................................................36

1.3.3 Open Tank Measurement..........................................................................................38

1.3.4 Closed Tank Measurement .......................................................................................39

1.3.5 Bubbler Level Measurement System ........................................................................44

1.3.6 Effect of Temperature on Level Measurement ..........................................................46

1.3.7 Effect of Pressure on Level Measurement ................................................................49

1.3.8 Level Measurement System Errors............................................................................49

1.4 TEMPERATURE MEASUREMENT..............................................................................51

1.4.1 Resistance Temperature Detector (RTD)..................................................................51

1.4.2 Thermocouple (T/C) ..................................................................................................54

1.4.3 Thermal Wells............................................................................................................56

1.4.4 Thermostats...............................................................................................................57

REVIEW QUESTIONS - EQUIPMENT ..............................................................................61

Module 2 - CONTROL

2.0 INTRODUCTION .........................................................................................................66

2.1 BASIC CONTROL PRINCIPLES .................................................................................66

2.1.1 Feedback Control.......................................................................................................68

2.1.2 Feedforward Control..................................................................................................68

2.1.3 Summary ...................................................................................................................68

2.2 ON/OFF CONTROL .....................................................................................................69

2.2.1 Summary ...................................................................................................................70

2.3 BASIC PROPORTIONAL CONTROL ..........................................................................71

2.3.1 Summary ...................................................................................................................73

2.4 Proportional Control .....................................................................................................74

2.4.1 Terminology...............................................................................................................74

2.4.2 Practical Proportional Control ...................................................................................74

2.4.3 Summary ...................................................................................................................81

2.5 Reset of Integral Action.................................................................................................81

2.5.1 Summary ...................................................................................................................85

2.6 RATE OR DERIVATIVE ACTION ................................................................................85

2.6.1 Summary ...................................................................................................................90

2.7 MULTIPLE CONTROL MODES....................................................................................90

2.8 TYPICAL NEGATIVE FEEDBACK CONTROL SCHEMES……………………………..91

2.8.1 Level Control ............................................................................................................91

2.8.2 Flow Control ..............................................................................................................92

2.8.3 Pressure Control........................................................................................................93

2.8.4 Temperature Control..................................................................................................94

REVIEW QUESTIONS - CONTROL ..................................................................................95

Module 3  Analog electronic instrumentation

3.1 4 to 20 mA analog current signals…………………………………………………………98

3.2 Relating 4 to 20 mA signals to instrument variables …………..………………………101

3.2.1 Example calculation: controller output to valve ……………………………………...101

3.2.2 Example calculation: flow transmitter………………………..………………………..102

3.2.3 Example calculation: temperature transmitter…………………..……………………103

3.2.4 Example calculation: pH transmitter ………………………………..…………………103

3.2.5 Example calculation: reverse-acting I/P transducer signal…………….……………104

3.2.6 Graphical interpretation of signal ranges……………………………………...………105

3.3 Controller output current loops …………………………………………………………..107

3.4 4-wire (“self-powered”) transmitter current loops ………………………………………109

3.5 2-wire (“loop-powered”) transmitter current loops ……………………………………..110

3.6 Troubleshooting current loops …………………………………………………………...112

3.6.1 Using a standard milliammeter to measure loop current ………………………...…114

3.6.2 Using a clamp-on milliammeter to measure loop current ……………………..……116

3.6.3 Using “test” diodes to measure loop current …………………………………..……..117

3.6.4 Using shunt resistors to measure loop current ………………………………………119

3.6.5 Troubleshooting current loops with voltage measurements……………………...…120

3.6.6 Using loop calibrators ……………………………………………………..…………....124

3.6.7 NAMUR signal levels ………………………….………………………………………..129

Module  4  Digital data acquisition and networks

4.1 Digitization of analog quantities………………………………………………………….131

4.1.1 Resolution ……………………………………………………………..………………...131

4.1.2 Sampling rate ……………………………………………………………...…………….136

4.2 Digital data communication theory ………………………………………………………138

4.2.1 Serial communication principles ………………………………………...…………….140

4.2.2 Physical encoding of bits ……………………………………………………….………143

4.2.3 Communication speed ……………………………………………………………….…146

4.2.4 Data frames ……………………………………………………………………………...148

4.2.5 Channel arbitration………………………………………………………………………157

4.2.6 Code sets ………………………………………………………………………………..163

4.2.7 The OSI Reference Model …………………………………………………..…………166

4.3 EIA/TIA-232, 422, and 485 networks ……………………………………………………168

4.3.1 EIA/TIA-232 ……………………………………………………………………….……..170

4.3.2 EIA/TIA-422 and EIA/TIA-485………………………….……………...……………….173

4.4 Ethernet networks……………………………………………………………….…………180

4.4.1 Repeaters (hubs)…………………………………………………………………….…. 181

4.4.2 Ethernet cabling ………………………….………………………………………………183

4.4.3 Switching hubs………………………………………………………………………….. 186

4.5 Internet Protocol (IP)………………………….……………………………………………188

4.5.1 IP addresses……………………………………………………………………………..189

4.5.2 Subnetworks and subnet masks…………………………………………………….…193

4.5.3 IP version 6 ……………………………………………………………………..……….196

4.5.4 DNS……………………………………………………………………………...….........196

4.5.5 Command-line diagnostic utilities………………………………………………..…….197

4.6 Transmission Control Protocol (TCP) and User Datagram Protocol (UDP) ……..…199

4.7 The HART digital/analog hybrid standard……………………………………………….201

4.7.1 HART multidrop mode…………………………………………………………………..208

4.7.2 HART multi-variable transmitters ………………………………………………..........209

4.8 Modbus…………………………………………………………………………………...…210

4.8.1 Modbus data frames…………………………………………………………………….210

4.8.2 Modbus function codes and addresses……………….………………………………212

4.8.3 Modbus function command formats …………………………………………………..213

Module 5 Smart Transmitter

5.1    Definitions ……………………………………………………….………..……………..220

5.2.1 Selection, Calibration and installation  …………………………………………….….224

5.2.2 Reference Condition Accuracy  …………………...…………………………………..225

5.2.3 Thermal  errors………………………………………………………………..…………225

5.2.4 Application specific errors ………………………………...……………………………225

5.2.5 Analog units ………………………………………………………………..……………226

5.2.6 Calibration………………………………………………………………………………..228

5.2.7 Calibration Equipment………………………………………………………..…………105

5.3 Calibrating Hart Transmitters …………………………..………………………………..234

5.3.1 Calibration concepts………………………………………… …………………………234

5.3.2 Error Calculation …………………………..……………………………………………..235

5.3.3  HART fundamentals…………………………….…………………….……….………..238

5.3.4 Calibrating a Conventional Instrument……………………………………...…………240

5.3.5 Calibrating HART Instrument ………………………………………….....……………240

5.3.6 HART Calibration Requirement ………………………………...……………………..242

5.3.7 Calibrating the Input Section ………………………………………..…………………243

5.3.8 Calibrating the Output Section…………………………………………………………243

5.3.9 Testing overall Performance ………………………………………………..…………243

5.3.10 Effect of Damping on test Performance……………………………. ………………244

5.3. 11 Operations that are Not proper Calibration………………...……………… ………244

5.3.5 Calibrating HART Instrument …………………………………………….....…………240

5.3.6 HART Calibration Requirement ………………………………...……………………..242

5.3.7 Calibrating the Input Section …………………………………………..………….……243

5.3.8 Calibrating the Output Section…………………………………………………………243

5.3.9 Testing overall Performance ………………………………………………..…………243

5.3.10 Effect of Damping on test Performance……………………… …… ………………244

Module 6  Progress of International Standardization of Fieldbus…………………….248

6.1.1 what is Fieldbus………………………………..…………………………………………249

6.1.2 Progress of Fieldbus Standardization……...........................................................250

6.1.2 Recognition as a Standardization Work Item ……………..………..…………………250

6.2    Process of Standardization...……………………………………………………………251

6.2.1 Fieldbus Standard Specifications……………..…………………..…………………….252

6.2.2 IEC/ISA Standard Specifications…………………………………..……………………252

6.3 Features of Fieldbus ………………………………………………..………………….…253

6.3.1 Comparison with Conventional Communication………………………………………148

6.3.2 Reduced Wiring Cost ……..……………………………………..……………………..256

6.3.3 Multi-drop Conn …………….………………………………….……………………….256

6.3.4 Multivariable Detection and Transmission………………..…..……………………….256

6.3.5 Fieldbus Communication Systems  ……..…………………...……………………….257

6.3.6 Improved Transmission Accuracy…………….…………………..…………………….256

6.3.7 Removing Error Factors……………………………………………..………………….258

6.3.8 Enhanced Data Transmission  ……..……………..………………...………………….257

6.3.9 Distributed Functions…………………………………………………….……..………..260

6.3.10 Fieldbus Communication Systems  ……..……………………………...…………….257

6.3.11 Interoperability…………….……………………………………………..…………….261

Appendix A : Application of Smart Devices in Fiscal and Custody Transfer of Natural Gas

Energy Measurement Using Flow Computers and Chromatography………………262

Appendix B : Application of Smart Devices Maintenance and Calibration

Using 744 Process Calibrator  for Calibration of HART Field Instrumentation……272