Fluke 8842a User Manual

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8842A

Digital Multimeter

Instruction Manual

PN 879309 Date December 1991 Rev.3 7/96

Chapter Title Page

1 Introduction and Specifications ........................................................ 1-1

1-1. INTRODUCTION................................................................................ 1-2

1-2. THE 8842A DIGITAL MULTIMETER.............................................. 1-2

1-3. OPTIONS AND ACCESSORIES........................................................ 1-2

1-4. SPECIFICATIONS .............................................................................. 1-3

2 Operating Instructions....................................................................... 2-1

2-1. INTRODUCTION................................................................................ 2-2

2-2. INSTALLATION................................................................................. 2-2

2-3. Installing the Power-Line Fuse ........................................................ 2-2

2-4. Connecting to Line Power................................................................ 2-2

2-5. Adjusting the Handle........................................................................ 2-3

2-6. Rack Mounting Kits......................................................................... 2-3

2-7. OPERATING FEATURES .................................................................. 2-4

2-8. Power-Up Features........................................................................... 2-4

2-9. Front and Rear Panel Features......................................................... 2-4

2-10. Display Features............................................................................... 2-8

2-11. Error Messages................................................................................. 2-8

2-12. Overrange Indication........................................................................ 2-10

2-13. Diagnostic Self-Tests....................................................................... 2-10

2-14. Ranging............................................................................................ 2-10

2-15. AUTORANGE............................................................................. 2-10

2-16. MANUAL RANGE..................................................................... 2-11

2-17. Triggering......................................................................................... 2-11

2-18. CONTINUOUS TRIGGER MODE ............................................ 2-11

2-19. EXTERNAL TRIGGER MODE ................................................. 2-11

2-20. Reading Rates and Noise Rejection................................................. 2-11

2-21. Automatic Settling Time Delay........................................................ 2-12

2-22. External Trigger Input (Option -05 Only)........................................ 2-12

2-23. Sample Complete Output (Option -05 Only)................................... 2-12

2-24. MAKING MEASUREMENTS............................................................ 2-13

2-25. Input Overload Protection Limits..................................................... 2-13

2-26. Measuring Voltage and Resistance.................................................. 2-13

2-27. Measuring Current ........................................................................... 2-13

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2-28. Current Fuse Protection.................................................................... 2-13

2-29. Offset Measurements....................................................................... 2-14

2-30. EXTERNAL CLEANING.................................................................... 2-15

3 Remote Programming........................................................................ 3-1

3-1. INTRODUCTION................................................................................ 3-3

3-2. CAPABILITIES................................................................................... 3-3

3-3. BUS SET-UP PROCEDURE............................................................... 3-3

3-4. AN OVERVIEW OF REMOTE OPERATION................................... 3-4

3-5. A NOTE ABOUT EXAMPLES........................................................... 3-6

3-6. DEVICE-DEPENDENT COMMAND SET ........................................ 3-6

3-7. Bn (Offset Commands).................................................................... 3-9

3-8. Cn (Calibration Commands)............................................................ 3-9

3-9. Dn (Display Commands).................................................................. 3-9

3-10. Fn (Function Commands) ................................................................ 3-10

3-11. Get Commands................................................................................. 3-10

3-12. G0 (Get Instrument Configuration).................................................. 3-12

3-13. G1 (Get SRQ Mask)......................................................................... 3-12

3-14. G2 (Get Calibration Prompt)............................................................ 3-12

3-15. G3 (Get User-Defined Message)...................................................... 3-13

3-16. G4 (Get Calibration Status).............................................................. 3-13

3-17. G5 (Get IAB Status)......................................................................... 3-14

3-18. G6 (Get YW Status)......................................................................... 3-14

3-19. G7 (Get Error Status)....................................................................... 3-14

3-20. G8 (Get Instrument Identification)................................................... 3-14

3-21. N (Numeric Entry Command).......................................................... 3-15

3-22. Put Commands................................................................................. 3-15

3-23. P0 (Put Instrument Configuration)................................................... 3-15

3-24. P1 (Put SRQ Mask).......................................................................... 3-16

3-25. P2 (Put Calibration Value).............................................................. 3-16

3-26. P3 (Put User-Defined Message)...................................................... 3-17

3-27. Rn (Range Commands).................................................................... 3-17

3-28. Sn (Reading Rate Commands)......................................................... 3-17

3-29. Tn (Trigger Mode Commands)........................................................ 3-17

3-30. Wn (Terminator Commands)........................................................... 3-19

3-31. X0 (Clear Error Register Command)............................................... 3-19

3-32. Yn (Suffix Commands).................................................................... 3-19

3-33. Z0 (Self-Test Command)................................................................. 3-19

3-34. (Device-Clear Command)................................................................ 3-20

3-35. ? (Single-Trigger Command)........................................................... 3-20

3-36. INPUT SYNTAX................................................................................. 3-20

3-37. Definitions........................................................................................ 3-20

3-38. Input Processing............................................................................... 3-21

3-39. Syntax Rules .................................................................................... 3-23

3-40. OUTPUT DATA.................................................................................. 3-24

3-41. Loading Output Data........................................................................ 3-24

3-42. Types of Output Data....................................................................... 3-25

3-43. Numeric Data and Error Messages................................................... 3-25

3-44. MEASUREMENT DATA........................................................... 3-25

3-45. OVERRANGE INDICATION .................................................... 3-26

3-46. ERROR MESSAGES.................................................................. 3-26

3-47. Status Data ....................................................................................... 3-26

3-48. Output Priority ................................................................................. 3-26

3-49. SERVICE REQUESTS........................................................................ 3-27

Contents

3-50. The Serial Poll Register ................................................................... 3-27

3-51. The SRQ Mask................................................................................. 3-28

3-52. INTERFACE MESSAGES.................................................................. 3-29

3-53. Address Messages............................................................................ 3-29

3-54. Universal Commands....................................................................... 3-29

3-55. Addressed Commands...................................................................... 3-30

3-56. TALK-ONLY MODE.......................................................................... 3-30

3-57. REMOTE CALIBRATION.................................................................. 3-31

3-58. TIMING CONSIDERATIONS............................................................ 3-31

3-59. IMMEDIATE MODE COMMANDS.................................................. 3-31

3-60. EXAMPLE PROGRAMS.................................................................... 3-32

4 Measurement Tutorial........................................................................ 4-1

4-1. INTRODUCTION................................................................................ 4-2

4-2. DC VOLTAGE MEASUREMENT ..................................................... 4-2

4-3. Circuit Loading Error....................................................................... 4-2

4-4. Input Bias Current Error................................................................... 4-3

4-5. RESISTANCE MEASUREMENT ...................................................... 4-4

4-6. 2-Wire Ohms.................................................................................... 4-4

4-7. Correcting for Test Lead Resistance in 2-Wire Ohms..................... 4-5

4-8. 4-Wire Ohms.................................................................................... 4-5

4-9. Applications of the Ohms Functions................................................ 4-7

4-10. TESTING DIODES..................................................................... 4-7

4-11. TESTING ELECTROLYTIC CAPACITORS............................ 4-7

4-12. A PRECISION CURRENT SOURCE......................................... 4-8

4-13. DC CURRENT MEASUREMENT ..................................................... 4-8

4-14. REDUCING THERMAL VOLTAGES............................................... 4-9

4-15. AC VOLTAGE AND CURRENT MEASUREMENT........................ 4-10

4-16. True RMS Measurement.................................................................. 4-10

4-17. Waveform Comparison.................................................................... 4-10

4-18. Crest Factor...................................................................................... 4-12

4-19. AC-Coupled AC Measurements ...................................................... 4-12

4-20. Combined AC and DC Measurements............................................. 4-13

4-21. Bandwidth........................................................................................ 4-13

4-22. Zero-Input VAC Error...................................................................... 4-13

4-23. MAKING ACCURATE MEASUREMENTS ON THE 20 mV

AND 20Ω RANGES ............................................................................ 4-14

4-24. MAKING ACCURATE HIGH-RESISTANCE MEASUREMENTS . 4-15

(continued)

5 Theory of Operation........................................................................... 5-1

5-1. INTRODUCTION................................................................................ 5-3

5-2. OVERALL FUNCTIONAL DESCRIPTION...................................... 5-3

5-3. DETAILED CIRCUIT DESCRIPTION .............................................. 5-4

5-4. DC SCALING...................................................................................... 5-4

5-5. VDC Scaling.................................................................................... 5-6

5-6. VDC Protection................................................................................ 5-7

5-7. mA DC Scaling................................................................................ 5-7

5-8. Analog Filter.................................................................................... 5-7

5-9. TRACK/HOLD CIRCUIT ................................................................... 5-8

5-10. Track Configuration......................................................................... 5-10

5-11. Settling Configuration...................................................................... 5-11

5-12. Hold Configuration.......................................................................... 5-11

5-13. Pre-Charge Configuration................................................................ 5-11

5-14. PRECISION VOLTAGE REFERENCE.............................................. 5-11

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5-15. OHMS CURRENT SOURCE.............................................................. 5-12

5-16. OHMS PROTECTION......................................................................... 5-13

5-17. OHMS FUNCTIONS........................................................................... 5-13

5-18. 2-Wire Ohms.................................................................................... 5-13

5-19. 4-Wire Ohms.................................................................................... 5-15

5-20. A/D CONVERTER.............................................................................. 5-15

5-21. Timing/Data Control........................................................................ 5-17

5-22. Precision DAC ................................................................................. 5-18

5-23. A/D Amplifier.................................................................................. 5-18

5-24. Bootstrap Supplies ........................................................................... 5-18

5-25. DISPLAY............................................................................................. 5-19

5-26. KEYBOARD........................................................................................ 5-19

5-27. DIGITAL CONTROLLER................................................................... 5-19

5-28. In-Guard Microcomputer................................................................. 5-21

5-29. Function and Range Control............................................................ 5-23

5-30. A/D Control and Computation......................................................... 5-23

5-31. Calibration Correction...................................................................... 5-23

5-32. Keyboard/Display Control............................................................... 5-24

5-33. Troubleshooting Modes ................................................................... 5-24

5-34. Guard-Crossing Communication..................................................... 5-24

5-35. GUARD CROSSING........................................................................... 5-24

5-36. POWER SUPPLY................................................................................ 5-25

5-37. IEEE-488 INTERFACE (OPTION -05)............................................... 5-26

5-38. Out-Guard Microcomputer............................................................... 5-26

5-39. Guard Crossing................................................................................. 5-26

5-40. Bus Interface Circuitry..................................................................... 5-26

5-41. Signal Conditioning ......................................................................... 5-27

5-42. IEEE-488 Interface Power Supply................................................... 5-27

5-43. TRUE RMS AC (OPTION -09)........................................................... 5-27

5-44. VAC Scaling.................................................................................... 5-27

5-45. mA AC Scaling................................................................................ 5-28

5-46. Frequency Response Trimming ....................................................... 5-28

5-47. True RMS AC-to-DC Conversion ................................................... 5-28

6 Maintenance....................................................................................... 6-1

6-1. INTRODUCTION................................................................................ 6-3

6-2. PERFORMANCE TEST...................................................................... 6-4

6-3. Diagnostic Self-Tests....................................................................... 6-4

6-4. DC Voltage Test............................................................................... 6-5

6-5. AC Voltage Test (Option -09 Only)................................................. 6-7

6-6. Resistance Test................................................................................. 6-8

6-7. DC Current Test............................................................................... 6-9

6-8. AC Current Test (Option -09 Only)................................................. 6-10

6-9. CALIBRATION................................................................................... 6-10

6-10. Basic Calibration Procedure............................................................. 6-11

6-11. INITIAL PROCEDURE.............................................................. 6-11

6-12. A/D CALIBRATION .................................................................. 6-12

6-13. OFFSET AND GAIN CALIBRATION ...................................... 6-14

6-14. HIGH-FREQUENCY AC CALIBRATION................................ 6-15

6-15. Advanced Features and Special Considerations............................... 6-16

6-16. STORING VARIABLE INPUTS................................................ 6-16

6-17. CALIBRATING INDIVIDUAL RANGES................................. 6-17

6-18. VERIFYING CALIBRATION.................................................... 6-17

6-19. ERASING CALIBRATION MEMORY..................................... 6-18

Contents

6-20. TOLERANCE CHECK............................................................... 6-18

6-21. AC CALIBRATION AT OTHER FREQUENCIES ................... 6-19

6-22. OPTIMIZING USE OF THE 5450A........................................... 6-19

6-23. Remote Calibration.......................................................................... 6-20

6-24. TIMING CONSIDERATIONS ................................................... 6-23

6-25. REMOTE ERASURE.................................................................. 6-24

6-26. EXAMPLE CALIBRATION PROGRAM.................................. 6-24

6-27. DISASSEMBLY PROCEDURE.......................................................... 6-25

6-28. Case Removal................................................................................... 6-26

6-29. True RMS AC PCA Removal (Option -09 Only)............................ 6-30

6-30. IEEE-488 Interface PCA Removal (Option -05 Only) .................... 6-30

6-31. Main PCA Removal......................................................................... 6-30

6-32. Front Panel Disassembly.................................................................. 6-32

6-33. REASSEMBLY PROCEDURE........................................................... 6-32

6-34. INTERNAL FUSE REPLACEMENT ................................................. 6-36

6-35. EXTERNAL TRIGGER POLARITY SELECTION (Option -05 Only)6-36

6-36. TROUBLESHOOTING....................................................................... 6-36

6-37. Initial Troubleshooting Procedur e.................................................... 6-36

6-38. Diagnostic Self-Tests....................................................................... 6-41

6-39. Self-Test Descriptions...................................................................... 6-42

6-40. Digital Controller Troubleshooting.................................................. 6-45

6-41. IN-GUARD MICROCOMPUTER SYSTEM............................. 6-45

6-48. DISPLAY SYSTEM.................................................................... 6-49

6-59. ANALOG CONTROL SIGNALS............................................... 6-51

6-62. DC Scaling Troubleshooting............................................................ 6-54

6-63. Track/Hold Troubleshooting............................................................ 6-56

6-64. Ohms Current Source Troubleshooting............................................ 6-56

6-65. Precision Voltage Reference Troubleshoo ting................................. 6-58

6-66. A/D Converter Troubleshooting....................................................... 6-59

6-67. Power Supply Troubleshooting........................................................ 6-61

6-68. IEEE-488 Interface Troubleshooting (Option -05).......................... 6-64

6-69. SERVICE POSITION.................................................................. 6-64

6-70. DIAGNOSTIC PROGRAM ........................................................ 6-64

6-71. True RMS AC Troubleshooting (Option -09).................................. 6-66

6-72. SERVICE POSITION.................................................................. 6-66

6-73. MAJOR PROBLEMS.................................................................. 6-67

6-74. MORE OBSCURE PROBLEMS ................................................ 6-69

6-75. Guard Crossing Troubleshooting..................................................... 6-70

6-76. INTERNAL CLEANING..................................................................... 6-70

6-77. Cleaning Printed Circuit Assemblies............................................... 6-70

6-78. Cleaning After Soldering................................................................. 6-71

(continued)

7 List of Replaceable Parts................................................................... 7-1

7-1. INTRODUCTION................................................................................ 7-3

7-2. HOW TO OBTAIN PARTS................................................................. 7-3

7-3. MANUAL STATUS INFORMATION................................................ 7-3

7-4. NEWER INSTRUMENTS................................................................... 7-4

7-5. SERVICE CENTERS........................................................................... 7-4

8 Options and Accessories.................................................................. 8-1

8-1. INTRODUCTION................................................................................ 8-3

8-2. ACCESSORIES ................................................................................... 8-4

8-3. Rack-Mount Kits (Y8834, Y8835 and Y8836)................................ 8-4

8-4. Shielded IEEE-488 Interface Cables (Y8021, Y8022, and Y8023). 8-4

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8-5. Replacement Test Leads (TL70A)................................................... 8-4

8-6. Deluxe Test Lead Kits (Y8134)....................................................... 8-4

8-7. Slim-Flex Test Leads (Y8140)......................................................... 8-4

8-8. Temperature Probes (80T-150U, and 80TK.).................................. 8-4

8-9. RF Probes (85RF and 83RF)............................................................ 8-4

8-10. Current Shunt (80J-10)..................................................................... 8-5

8-11. Current Probes (Y8100, Y8101, 80i-400 and 80i-600).................... 8-5

8-12. High Voltage Probes (80K-6 and 80K-40) ...................................... 8-5

805 Option –05 IEEE-488 Interface........................................................... 805-1

805-1. INTRODUCTION................................................................................ 805-3

805-2. CAPABILITIES ................................................................................... 805-3

805-3. EXTERNAL CONTROLS................................................................... 805-3

805-4. INSTALLATION................................................................................. 805-3

805-5. PROGRAMMING INSTRUCTIONS.................................................. 805-4

805-6. MAINTENANCE................................................................................. 805-4

805-7. LIST OF REPLACEABLE PARTS..................................................... 805-4

809 Option –09 True RMS AC................................................................... 809-1

809-1. INTRODUCTION................................................................................ 809-3

809-2. INSTALLATION................................................................................. 809-3

809-3. OPERATING INSTRUCTIONS .......................................................... 809-4

809-4. MAINTENANCE................................................................................. 809-4

809-5. LIST OF REPLACEABLE PARTS..................................................... 809-4

9 Schematic Diagrams.......................................................................... 9-1

List of Tables

Table Title Page

2-1. Error Codes............................................................................................................ 2-9

2-2. Input Overload Limits............................................................................................ 2-13

3-1. Status Data............................................................................................................. 3-11

3-2. Numeric Output Data Format................................................................................ 3-25

3-8. Serial Poll Register ................................................................................................ 3-28

3-3. Immediate-Mode Commands for Various Controllers.......................................... 3-32

3-4. ASCII/IEEE Std 488-1978 Bus Codes .................................................................. 3-49

4-1. Ohms Test Current................................................................................................. 4-6

5-1. Sample Rates and Reading Rates........................................................................... 5-23

6-1. Recommended Test Equipment............................................................................. 6-3

6-2. DC Voltage Test .................................................................................................... 6-6

6-3. Low- and Mid-Frequency AC Voltage Test.......................................................... 6-7

6-4. High-Frequency AC Voltage Test......................................................................... 6-8

6-5. Resistance Test...................................................................................................... 6-9

6-6. DC Current Test..................................................................................................... 6-9

6-7. AC Current Test..................................................................................................... 6-10

6-8. A/D Calibration Steps............................................................................................ 6-13

6-9. A/D Calibration Verification Test......................................................................... 6-13

6-10. Offset and Gain Calibration Steps ......................................................................... 6-14

6-11. High-Frequency AC Calibration Steps.................................................................. 6-16

6-12. Prompts When Calibrating Individual Ranges....................................................... 6-17

6-13. Tolerance Limits.................................................................................................... 6-19

6-14. Commands Used During remote Calibration......................................................... 6-21

6-15. Error Numbers Which Are Displayed When Commands Are Not Valid.............. 6-23

6-16. Overall State Table................................................................................................ 6-38

6-17. Circuitry Tested by the Analog Self-Tests............................................................. 6-40

6-18. Self-Test Voltages.................................................................................................. 6-42

6-19. Keyboard Wiring ................................................................................................... 6-51

6-20. Analog Control Devices......................................................................................... 6-52

6-21. Analog Control Logic States.................................................................................. 6-53

6-22. DC Scaling and Track/Hold Supply Voltages ....................................................... 6-55

6-23. Power Supply Voltages.......................................................................................... 6-63

6-24. Diagnostic Modes.................................................................................................. 6-65

6-25. I/O Port Configurations ......................................................................................... 6-66

6-26. Isolating a Defective AC Stage.............................................................................. 6-67

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6-27. AC Signal Tracing................................................................................................. 6-68

6-28. Truth Table for U804 and K2................................................................................ 6-69

7-1. 8842A Digital Multimeter...................................................................................... 7-5

7-2. A1 Main PCA........................................................................................................ 7-10

7-3. A2 Display PCA.................................................................................................... 7-14

8-1. Accessories ............................................................................................................ 8-3

8-2. Options................................................................................................................... 8-3

805-1.Option -05A IEEE-488 Interface PCA.................................................................. 805-7

809-1.Option -09 True RMS AC PCA............................................................................. 809-6

viii

List of Figures

Figure Title Page

1-1. External Dimensions.............................................................................................. 1-11

2-1. Line Voltage Selection Settings............................................................................. 2-2

2-2. Adjusting the Handle............................................................................................. 2-3

2-3. Rack-Mount Kits.................................................................................................... 2-3

2-4. Installing the Single Rack Mount Kit .................................................................... 2-4

2-5. Front Panel Features .............................................................................................. 2-5

2-6. Rear Panel Features ............................................................................................... 2-7

2-7. Typical Error Messages......................................................................................... 2-8

2-8. Overrange Indication ............................................................................................. 2-12

2-9. Measuring Voltage and Resistance........................................................................ 2-15

2-10. Measuring Current................................................................................................. 2-15

3-1. IEEE-488 Address Selection.................................................................................. 3-4

3-2. Remote Operation Block Diagram......................................................................... 3-5

3-3. Typical Command String....................................................................................... 3-6

3-4. Commands Which Correspond to the Front Panel................................................. 3-7

3-5. Device-Dependent Command Set.......................................................................... 3-8

3-6. Output Data Format............................................................................................... 3-10

3-6. Trigger Selection Logic Diagram.......................................................................... 3-18

3-7. Interpretation of Messages..................................................................................... 3-22

3-9. Example Program................................................................................................... 3-33

3-10. Example Program: Taking Readings with Local Control...................................... 3-34

3-11. Example Program: Using the Serial Poll Register................................................. 3-35

3-12. Example Program: Record Errors During Selftest................................................. 3-36

3-13. Example Programs: Using the IBM PC................................................................. 3-37

4-1. Circuit Loading Error Calculation......................................................................... 4-2

4-2. Measuring Input Bias Current Error...................................................................... 4-3

4-3. Wire Ohms Measurement...................................................................................... 4-4

4-4. Wire Ohms Measurement...................................................................................... 4-6

4-5. Burden Voltage Error Calculation......................................................................... 4-9

4-6. Waveform Comparison Chart................................................................................ 4-11

4-7. Typical Crest Factors for Various Waveforms...................................................... 4-12

4-8. Combined AC and DC Measurement.................................................................... 4-13

4-9. Reduction of Zero-Input Error............................................................................... 4-14

4-10. Shielding for Low Voltage Measurements............................................................ 4-15

4-11. Shielding for Low Resistance Measurements........................................................ 4-15

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4-12. Leakage Resistance in High Resistance Measurement.......................................... 4-16

5-1. Overall Functional Block Diagram........................................................................ 5-5

5-2. DC Scaling (VDC and mA DC)............................................................................. 5-6

5-3. Track/Hold Amplifier............................................................................................ 5-8

5-4. Track/Hold Circuit Configurations........................................................................ 5-9

5-5. Timing Diagram for One A/D Cycle..................................................................... 5-10

5-6. Precision Voltag e Reference.................................................................................. 5-11

5-7. Ohms Current Source............................................................................................. 5-12

5-8. Ohms Scaling......................................................................................................... 5-14

5-9. Analog-to-Digital Converter.................................................................................. 5-16

5-10. First Remainder-Store Period ................................................................................ 5-17

5-11. Autozero Period..................................................................................................... 5-18

5-12. Vacuum Fluorescent Display................................................................................. 5-19

5-13. Digital Controller Block Diagram.......................................................................... 5-20

5-14. Read/Write Timing Diagrams for Internal Bus...................................................... 5-22

5-15. Guard Crossing Circuit.......................................................................................... 5-24

5-16. IEEE-488 Interface Block Diagram....................................................................... 5-26

5-17. True RMS AC Option Block Diagram.................................................................. 5-27

5-18. True RMS AC-to-DC Converter............................................................................ 5-28

6-1. DC Calibration Connections.................................................................................. 6-6

6-2. First A/D Calibration Prompt................................................................................. 6-11

6-3. Calibration Functions............................................................................................. 6-12

6-4. Optimizing Use of the 5450A................................................................................ 6-20

6-5. Example A/D Calibration Program........................................................................ 6-25

6-6. 8842A Disassembly............................................................................................... 6-26

6-7. Front Panel Disassembly........................................................................................ 6-34

6-8. Removing the Display Window............................................................................. 6-35

6-9. U202 Pin Diagram................................................................................................. 6-46

6-10. Waveforms for In-Guard Troubleshooting Mode.................................................. 6-47

6-11. Waveforms for Display Logic ............................................................................... 6-49

6-12. Typical Dynamic Control Signals.......................................................................... 6-54

6-13. Typical Output Waveforms for Track/Hold Circuit (TP103)................................ 6-57

6-14. Output of A/D Amplifier (TP101)......................................................................... 6-59

6-15. Waveforms at U101-24 and U101-25.................................................................... 6-60

6-16. Typical Bus Data Line Waveform......................................................................... 6-60

6-17. Waveforms at TP102 for Several Inputs on 2V DV Range................................... 6-62

6-18. Calculating the A/D Reading From TP102 Waveform.......................................... 6-63

6-19. Option -05 Service Position................................................................................... 6-65

6-20. Option -09 Service Position................................................................................... 6-68

6-21. Guard Crossing Test Waveforms........................................................................... 6-71

7-1. 8842A Digital Multimeter...................................................................................... 7-6

7-2. A1 Main PCA........................................................................................................ 7-13

7-3. A2 Display PCA.................................................................................................... 7-15

7-4. Service Centers...................................................................................................... 7-18

7-4. Service Centers (cont)............................................................................................ 7-19

805-1.Installing Option -05.............................................................................................. 805-5

805-2.IEEE-488 Interface PCA........................................................................................ 805-8

809-1.Installing Option -09.............................................................................................. 809-5

809-2.True RMS AC PCA ............................................................................................... 809-7

9-1. Main PCA, DC Scaling and F/R Switch................................................................ 9-3

9-2. Main PCA, A/D Converter .................................................................................... 9-5

9-3. Main PCA, Ohms Current Source ......................................................................... 9-7

9-4. Main PCA, Digital................................................................................................. 9-9

9-5. Main PCA, Power Supply...................................................................................... 9-11

9-6. Display PCA.......................................................................................................... 9-13

Contents

9-7. IEEE-488 Interface PCA, Option -05.................................................................... 9-15

9-8. True RMS AC PCA, Option -09............................................................................ 9-17

(continued)

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Instruction Manual

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Chapter 1

Introduction and Specifications

Title Page

1-1. INTRODUCTION................................................................................1-2

1-2. THE 8842A DIGITAL MULTIMETER..............................................1-2

1-3. OPTIONS AND ACCESSORIES........................................................1-2

1-4. SPECIFICATIONS ..............................................................................1-3

1-1

8842A

Instruction Manual

1-1. INTRODUCTION

1-2. THE 8842A DIGITAL MULTIMETER

This manual provides complete operating instructions and service information for the 8842A. If you want to get started using your 8842A right away, proceed to the operating instructions in Section 2. If you intend to use the 8842A with the IEEE-488 Interface (Option -05), read Sections 2 and 3. This meter has been designed and tested according to IEC publication 348, Safety Requirements for Electronic Measuring Apparatus. This manual contains information and warnings which must be followed to ensure safe operation and retain the meter in safe condition.

The Fluke 8842A Digital Multimeter is a high-performance 5-1/2 digit instrument designed for general-purpose bench or systems applications. The 8842A is the top-of-theline DMM in the 8840A family. Using proprietary thin film resistor networks, a stable reference amplifier and stable active components, the 8842A offers superior measurement performance and stability. It also offers additional 20 mV, 20 ohm, and 200 mA dc ranges. Features of the 8842A include:

• Highly legible vacuum fluorescent display

• Intuitively easy front panel operation

• Basic dc accuracy of 0.003% for 1 year

• 2-wire and 4-wire resistance measurement

• DC current measurement

• Up to 100 readings per second

• Closed-case calibration (no internal adjustments)

• Built-in self-tests

1-3. OPTIONS AND ACCESSORIES

A number of options and accessories are available for the 8842A which can be easily installed at any time. The options include:

• IEEE-488 Interface (Option -05), featuring:

• Full programmability

• Simple and predictable command set

• Fast measurement throughput

• External Trigger input connector

• Sample Complete output connector

1-2

• Automated calibration

• Low cost

• True RMS AC (Option -09), featuring:

• AC voltage measurement

• AC current measurement

Accessories include a variety of rack mounting kits, probes, test leads, and cables. Full information about options and accessories can be found in Section 8.

1-4. SPECIFICATIONS

Specifications for the 8842A are given in Table 1-1. External dimensions are shown in Figure 1-1.

DC VOLTAGE Input Characteristics

Table 1-1. Specifications

Introduction and Specifications

SPECIFICATIONS

FULL SCALE 5ñ

RANGE

20 mV 19.9999 mV 0.1µV1 µV ≥10,000 MΩ

200 mV 199.999 mV 1µV 10 µV ≥10,000 MΩ

2V 1.99999V 10 µV 100 µV ≥10,000 MΩ

20V 19.9999V 100 µV1 mV≥10,000 MΩ

200V 199.999V 1 mV 10 mV 10 MΩ

1000V 1000.00V 10 mV 100 mV 10 MΩ

*4ñ digits at the fastest reading rate.

Accuracy

NORMAL (S) READING RATE ............. ±(% of Reading + Number of Counts)

RANGE 24 HOURî 23±1°C 90 DAY 23±5°C 1 YEAR 23±5°C 2 YEAR 23±5°C

20 mV

200 mV

2V 0.0015 + 2 0.0025 + 2 0.0030 + 2 0.0050 + 3

20V 0.0015 + 2 0.0030 + 2 0.0035 + 2 0.0060 + 3

DIGITS

0.0050 + 20

0.0030 + 2 0.0045 + 3 0.0070 + 3 0.0100 + 4

5ñ DIGITS 4ñ DIGITS*

0.0070 + 30

RESOLUTION

0.0100 + 30

INPUT

RESISTANCE

0.0120 + 40

200V 0.0015 + 2 0.0030 + 2 0.0035 + 2 0.0060 + 3

1000V 0.0020 + 2 0.0035 + 2 0.0045 + 2 0.0070 + 3

1. Relative to calibration standards.

2. Within one hour of dc zero, using offset control.

3. When offset control is not used the number of counts are 50, 70, 90 and 90 for 24 hours, 90 day, 1 year, and 2 year respectively.

4. When offset control is not used the number of counts are 5, 7, 9 for 24 hours, 90 day, 1 year, and 2 year respectively.

MEDIUM AND FAST RATES: ................In medium rate, add 3 counts (20 counts on 20 mV Range) to

number of counts. In fast rate, use 2 (4½ digit mode) counts

(30 counts on 20 mV range) for the number of counts

1-3

8842A

Instruction Manual

Operating Characteristics

TEMPERATURE COEFFICIENT ...........<(0.0006% of reading + 0.3 Count) per °C from 0°C to 18°C

and 28°C to 50°C.

MAXIMUM INPUT...................................1000V dc or peak ac on any range.

NOISE REJECTION................................Automatically optimized at power-up for 50, 60, or 400 Hz.

RATE READINGS/

SECONDî





2.5 Analog & Digital >98 dB 20V or 2x FS >140 dB 20 Digital >45 dB 1x FS >100 dB

FILTER NMRRï PEAK NM

SIGNAL

F 100 None _ 1x FS >60 dB

1. Reading rate with internal trigger and 60 Hz power line frequency. See “reading rates” for more detail.

2. Normal Mode Rejection Ratio, at 50 or 60 Hz ±0.1%. The NMRR for 400 Hz ±0.1% is 85 dB in S rate and 35 dB in M rate.

3. Common Mode Rejection Ratio at 50 or 60 Hz ±0.1%, with 1 kΩ in series with either lead. The CMRR is >140 dB at dc for all reading rates.

4. 20 volts or 2 times full scale whichever is greater, not to exceed 1000V.

5. Reading rate-1/3 rdg / sec. in the 20 mV, 20Ω, 200 mA dc ranges

6. Reading rate-1.25 rdg / sec. in the 20 mV, 20Ω, 200 mA dc ranges

TRUE RMS AC VOLTAGE (OPTION 8842A-09) Input Characteristics

RESOLUTIONRANGE FULL SCALE 5ñ

DIGITS

5ñ DIGITS 4ñ DIGITS*

IMPENDANCE

CMRRð

INPUT

1-4

200 mV 199.999 mV 1 µV 10 µV1 MΩ

2V 1.99999V 10 µV 100 µV Shunted

20V 19.9999V 100 µV1 mV By 200V 199.999V 1 mV 10 mV <100 pF 700V 700.00V 10 mV 100 mV

*4ñ digits at the fastest reading rate

Introduction and Specifications

Accuracy

NORMAL (s) READING RATE .............. ±(% of Reading + Number of Counts).

For sinewave inputs ≥10,000 counts1.

FREQUENCY 24 HOURS2 23±1°C 90 DAY 23±5°C 1 YEAR 23±5°C 2 YEARS ±5°C

20-45 1.2 + 100 1.2 + 100 1.2 + 100 1.2 + 100

45-200 0.3 + 100 0.35 + 100 0.4 + 100 0.5 + 100

200-20k

(200 mV range) 0.06 + 100 0.08 + 100 0.10 + 100 0.20 + 100

(2V-200V range) 0.05 + 80 0.07 + 80 0.08 + 80 0.15 + 80

(700V range) 0.06 + 100 0.08 + 100 0.10 + 100 0.20 + 100

20k-50k 0.15 + 120 0.19 + 150 0.21 + 200 0.25 + 250

50k-100k 0.4 + 300 0.5 + 300 0.5 + 400 0.5 + 500

1. For sinewave inputs between 1,000 and 10,000 counts, add to number of counts 100 counts for frequencies 20 Hz to 20 kHz, 200 counts for 20 kHz, and 500 counts for 50 kHz to 100 kHz.

SPECIFICATIONS

2. Relative to calibration standards.

MEDIUM AND FAST READING RATES........In medium rate, add 50 counts to number of counts. In the

fast rate the specifications apply for sinewave inputs

≥1000 (4½ digit PRGH FRXQWV and >100 Hz.

NONSINUSOIDAL INPUTS...........................For nonsinusoidal inputs ≥10,000 counts with frequency

components ≥100 kHz, add the following % of reading to the accuracy specifications.

FUNDAMENTAL

FREQUENCY

45 Hz to 20 kHz 20 Hz 0.05 0.15 0.3 20 Hz to 45 Hz and 20

kHz to 50 kHz

Operating Characteristics

MAXIMUM INPUT...................................700V rms, 1000V peak or 2 x 107 Volts-Hertz product

TEMPERATURE COEFFICIENT............±(% of reading + Number of Counts) per °C, to 18°C and 28°C

FOR INPUTS

1.0 TO 1.5 1.5 TO 2.0 2.0 TO 3.0

0.2 0.7 1.5

(whichever is less) for any range.

to 50°C.

20-20k 20k-50k 50k-100k

CREST FACTOR

FREQUENCY IN HERTZ

≥10,000 counts 0.019 + 9 0.021 + 9 0.027 + 10

≥1,000 counts 0.019 + 12 0.021 + 15 0.027 + 21

COMMON MODE REJECTION..............>60 dB at 50 or 60 Hz with 1 kΩ in either lead.

1-5

8842A

Instruction Manual

CURRENT Input Characteristics

DC Accuracy

RESOLUTIONRANGE FULL SCALE 5½

DIGITS

5½ DIGITS 4½ DIGITS

200 mA

199.999 mA 1 µA 10 µA

2000 mA 1999.99 mA 10 µA 100 µA

1. 4½ digits at the fastest reading rate.

2. The 200mA range is available for dc current only.

NORMAL (S) READING RATE...............±(% of reading + number of counts).

RANGE 90 DAYS 23±5°C 1 YEAR 23±5°C 2 YEARS 23±5°C

200 mA 0.04 + 40 0.05 + 40 0.08 + 40

2000 mA

≤1A 0.04 + 4 0.05 + 4 0.08+4

>1A 0.1 + 4 0.1 + 4 0.15+4

MEDIUM AND FAST READING RATES In medium reading rate, add 2 counts (20 counts on 200 mA

range) to number of counts. In fast reading rate, use 2 (4½

digit mode) counts (20 counts on 200 mA range) for number of counts.

AC Accuracy (Option –09)

NORMAL (S) READING RATE...............±(% of Reading + Number of Counts).

23±5°C, for sinewave inputs ≥10,000 counts

FREQUENCY IN HERTZ

20-45 45-100 100-5K*

ONE YEAR 2.0 + 200 0.5 + 200 0.4 + 200 TWO YEAR 3.0 + 300 0.7 + 300 0.6 + 300

*Typically 20 kHz

1. For sinewave inputs between 1,000 and 10,000 counts, add to number of counts 100 counts for frequencies 20 Hz to 5 kHz (typically 20 kHz).

1-6

Introduction and Specifications

SPECIFICATIONS

MEDIUM AND FAST READING RATES........In medium rate, add 50 counts to number of counts. In fast

reading rate, for sinewave inputs ≥1000 (4½ digit mode)

counts and frequencies >100 Hz, the accuracy is ±(0.4% of reading +30 (4½ digit mode) counts).

NONSINUSOIDAL INPUTS ...........................For nonsinusoidal inputs ≥10,000 counts with frequency

components ≤100 kHz, add the following % of reading to the accuracy specifications

FUNDAMENTAL

FREQUENCY

45 HZ to 5 kHz

20 Hz to 45 Hz

Operating Characteristics

TEMPERATURE COEFFICIENT............Less than 0.1 x accuracy specification per °C to 18°C and

MAXIMUM INPUT...................................2A dc or rms ac. Protected with 2A, 250V fuse accessible at

BURDEN VOLTAGE...............................1V dc or rms ac typical at full scale.

RESISTANCE Input Characteristics

RANGE FULL SCALE

5½ DIGITS

20Ω

200Ω 199.999Ω 1 mΩ 10 mΩ 1 mA

2 kΩ 1.99999 kΩ 10 mΩ 100 mΩ 1 mA

19.999Ω 0.1 mΩ 1 mΩ 1 mA

1.0 TO 1.5 1.5 TO 2.0 2.0 TO 3.0

0.05

0.2

28°C to 50°C.

front panel, and interval 3A, 600V fuse.

5½ DIGITS 4½ DIGITS

CREST FACTOR

0.15

0.7

RESOLUTION

CURRENT

THROUGH UNKNOWN

0.3

1.5

20 kΩ 19.9999 kΩ 100 mΩ 1Ω 100 µA

200 kΩ 199.999 kΩ 1Ω 10Ω 10 µA

2000 kΩ 1999.99 kΩ 10Ω 100Ω 5 µA

20 MΩ 19.9999 MΩ 100Ω 1 kΩ 0.5 µA

1. 4½ digits at the fastest reading rate.

2. Four-wire ohms only.

1-7

8842A

Instruction Manual

Accuracy

NORMAL (S) READING RATE...............±(% of Reading + Number of Counts)1.

RANGE 24 HOURS 23±1°C 90 DAY 23±5°C 1 YEAR 23±5°C 2 YEARS 23±1°C

20Ω

200Ω

0.007 + 30

0.0040 + 3

0.009 + 40

0.007 + 4

0.012 + 40

0.010 + 4

0.015 + 40

0.012 + 4

2 kΩ 0.0025 + 2 0.005 + 3 0.008 + 3 0.010 + 3

20 kΩ 0.0025 + 2 0.005 + 3 0.008 + 3 0.010 + 3

200 kΩ 0.0025 + 2 0.006 + 3 0.010 + 3 0.012 + 3

2000 kΩ 0.023 + 3 0.025 + 3 0.027 + 3 0.030 + 3

20 MΩ 0.023 + 3 0.040 + 4 0.042 + 4 0.050 + 4

1. Within one hour of ohms zero, using offset control.

2. Relative to calibration standards.

3. Applies to 4-wire ohms only.

4. When offset control is not used the number of counts are 50, 70, 90 and 90 for 24 hours,90 day, 1 year, and 2 year respectively.

5. When offset control is not used the number of counts are 5, 7, 9 and 9 for 24 hours, 90 day, 1 year, and 2 year respectively.

MEDIUM AND FAST READING RATES........In medium rate, add 2 counts to the number of counts for

the 200Ω through 200 kΩ ranges, 3 counts for the 2000 kΩ and 20 MΩ ranges, and 20 counts for the 20Ω range.

In fast reading rate, use 3 (4½ digit mode) counts for the number of counts for the 200Ω range, 20 (4½ digit mode) counts for the 20Ω range and 2 (4½ digit mode) counts for all other ranges.

Operating Characteristics

TEMPERATURE COEFFICIENT............Less than 0.1 x accuracy specification per °C from 0°C to 18°C

and 28°C to 50°C.

MEASUREMENT CONFIGURATION.....2-wire or 4-wire in all ranges accept 20Ω range. Only 4-wire

configuration is allowed in the 20Ω range.

OPEN CIRCUIT VOLTAGE ....................Less than 6.5V on the 20Ω through the 200 kΩ ranges. Les s

than 13V on the 2000 kΩ and 20 MΩ ranges.

INPUT PROTECTION.............................To 300V rms.

1-8

Introduction and Specifications

SPECIFICATIONS

Reading Rates

READING RATES WITH INTERNAL TRIGGER (readings per second)

RATE

POWER LINE FREQUECNCY

50 Hz 60 Hz 400 Hz

S 2.08 (.26)

M 16.7 (1.04)

2.5 (.31) 20 (1.25)

F 100 100 100

1. Sensed automatically at power-up.

2. In 20 mV, 20 ohm, and 200 mA DC ranges.

AUTORANGING

The 8842A autoranges up to the highest ranges in all funtions, down to the 200 mV range in the VDC and VAC funtions, and down to the 200 Ω ranges in the ohms funtions. To select the 20 mV dc, 20Ω, or 200 mA dc range, press the respective range button (or send the respective range command, if using the IEEE-488 option).

2.38 (.30)

19.0 (1.19)

AUTOMATIC SETTLING TIME DELAY

Time in milliseconds from single trigger to start of A/D conversion, Autorange off.

FUNCTION RANGE

READING RATE

SMF

VDC 20 mV 342 342 9 30

200 mV 342 61 9 5

2V-1000V 342 17 9 9

VAC All 551 551 551 30 (Note 2)

MA DC 200 mA 342 342 9 9

2000 mA 342 17 9 5

MA AC 2000 mA 551 551 551 30 (Note 2)

Ohms 20Ω 395 395 17 40

200Ω 395 106 17 5

2 kΩ 322 17 13 5

20 kΩ 342 17 13 5

200 kΩ 141 121 21 5

NUMBER OF COUNTS

FROM FINAL VALUE

2000 kΩ 141 101 81 10

20 MΩ 1020 964 723 10

1. Difference between first reading and final value for an in-range step change coincident with trigger. For slow reading rate. 50 counts for medium rate; 10 counts for fast rate.

1-9

8842A

Instruction Manual

EXTERNAL TRIGGER TIMING CHARACTERISTICS

The following diagram shows the nominal timing for the various processes which take place between an external trigger and data sent out on the IEEE-488 interface. Delays will vary if a second trigger comes before the data handshake is complete.

t1-1.wmf

NOTES: 1. Time for single trigger to start of A/D conversion.(See “Automatic Settling Time

Delay” on previous page.) If the delay is disabled by using the T3 or T4 command, then the delay is 1 ms±150 µs. When the 8842A is triggered with an IEEE-488 command (GET or ?), the automatic settling time delay begins after the trigger command has been processed and recognized.

2. A/D conversion time is dependent on the reading rate and power-line frequency:

RATE

50 Hz 60 Hz 400 Hz

S 472 (3800)* 395 (3195)* 414 (3300)*

M 52 (960)* 45 (795)* 47 (840)*

F777

*In 20 mV DC, 20Ω and 200 mA DC ranges.

3. Sample complete is a 2.5 µs pulse which indicates that the analog input may be changed for the next reading.

4. When talking to a fast controller.

A/D CONVERSION TIME (ms)

1-10

Introduction and Specifications

SPECIFICATIONS

GENERAL

COMMON MODE VOLTAGE..................1000V dc or peak ac, or 700V rms ac from any input to earth.

TEMPREATURE RANGE.......................0 to 50°C operating, -40 to 70°C storage.

HUMIDITY RANGE.................................80% RH from 0 to 35°C, 70% to 50°C.

WARMUP TIME......................................1 hour to rated specifications.

POWER ..................................................100, 120, 220, or 240V ac ±10% (250V ac maximum), switch

selectable at rear panel. 50, 60, or 400 Hz, automatically sensed at power-up. 20 VA maximum.

VIBRATION.............................................Meets requirements of MIL-T- 28800C for Type III, Class 3,

Style E equipment.

PROTECTION ........................................ANSI C39.5 AND IEC 348, Class I.

SIZE ........................................................8.9 cm high, 21.6 cm wide, 37.1 cm deep(3.47 in high, 8.5 in

wide, 14.6 in deep).

WEIGHT..................................................Net, 3.4 kg (7.5 lb); shipping, 5.0 kg (11 lb).

INCLUDED..............................................Line cord, test leads, Instruction/Service Manual, IEEE-488

Quick Reference Guide, (Option –05 only), and instrument

performance record.

IEEE-488 INTERFACE FUNTION ..........Option allows complete control and data output capability, and

supports the following interface funtion subsets: SH1,AH1, T5,

L4, SR1, RL1, DC1, DT1, E1, PP0, AND C0. ELECTROMAGNETIC COMPATIBILITYSpecifications apply when used in an environment with fields

strengths ≤ 1 V/m, (0.8 V/m for DC Current.) For fields

strengths up to 3 V/m, multiply floor adder by 12 for VDC and

Resistance and 200 for DC current. VAC and AC Current have

no adders up to 3 V/m.

Figure 1-1. External Dimensions

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1-11

Chapter 2

Operating Instructions

Title Page

2-1. INTRODUCTION................................................................................2-2

2-2. INSTALLATION.................................................................................2-2

2-3. Installing the Power-Line Fuse ........................................................2-2

2-4. Connecting to Line Power................................................................2-2

2-5. Adjusting the Handle........................................................................2-3

2-6. Rack Mounting Kits.........................................................................2-3

2-7. OPERATING FEATURES ..................................................................2-4

2-8. Power-Up Features...........................................................................2-4

2-9. Front and Rear Panel Features.........................................................2-4

2-10. Display Features...............................................................................2-8

2-11. Error Messages.................................................................................2-8

2-12. Overrange Indication........................................................................2-10

2-13. Diagnostic Self-Tests.......................................................................2-10

2-14. Ranging............................................................................................2-10

2-15. AUTORANGE.............................................................................2-10

2-16. MANUAL RANGE.....................................................................2-11

2-17. Triggering.........................................................................................2-11

2-18. CONTINUOUS TRIGGER MODE ............................................2-11

2-19. EXTERNAL TRIGGER MODE .................................................2-11

2-20. Reading Rates and Noise Rejection.................................................2-11

2-21. Automatic Settling Time Delay........................................................2-12

2-22. External Trigger Input (Option -05 Only)........................................2-12

2-23. Sample Complete Output (Option -05 Only)...................................2-12

2-24. MAKING MEASUREMENTS............................................................2-13

2-25. Input Overload Protection Limits.....................................................2-13

2-26. Measuring Voltage and Resistance..................................................2-13

2-27. Measuring Current ...........................................................................2-13

2-28. Current Fuse Protection....................................................................2-13

2-29. Offset Measurements.......................................................................2-14

2-30. EXTERNAL CLEANING....................................................................2-15

2-1

8842A

Instruction Manual

2-1. INTRODUCTION

2-2. INSTALLATION

2-3. Installing the Power-Line Fuse

This section provides instructions for installing and operating the 8842A. Refer to Section 4 for measurement considerations.

WARNING

FOR POWER-LINE VOLTAGES OF 198V TO 250V, THE POWERLINE FUSE MUST BE REPLACED WITH A 1/8A, 250V SLO-BLO FUSE FOR FIRE PROTECTION. TO AVOID ELECTRIC SHOCK, REMOVE THE POWER CORD BEFORE REPLACING THE EXTERNAL LINE FUSE.

The 8842A has a rear-panel power-line fuse in series with the power supply. A 1/4A, 250V slow-blow fuse is installed in the factory for operation from 90V to 132V. For operation with power-line voltages of 198V to 250V, the fuse must be replaced with a 1/8A, 250V slo-blow fuse.

To replace the power-line fuse, first remove the power cord. Then turn the rear-panel fuse cover 1/4-turn counterclockwise with a screwdriver.

For power-line voltages of 198V to 250V, use only a 1/4 x 1 1/4 (6.3mm x 32mm) fuse with at least a 100A breaking capacity.

2-4. Connecting to Line Power

TO AVOID SHOCK HAZARD, CONNECT THE INSTRUMENT POWER CORD TO A POWER RECEPTACLE WITH EARTH GROUND. TO AVOID INSTRUMENT DAMAGE, CHECK THAT THE REAR PANEL LINE VOLTAGE SELECTION SWITCHES ARE SET TO THE POWER-LINE VOLTAGE IN OUR AREA.

The 8842A can be configured to accept line power of 100, 120, 220, or 240V ac (+/-10%, 250V maximum) at 50, 60, or 400 Hz. The voltage must be selected by setting the rear panel LINE SET switches as shown in Figure 2-1. The 8842A automatically senses the power-line frequency at power-up, so that no adjustment for frequency is necessary.

WARNING

2-2

Figure 2-1. Line Voltage S election Settings

f2-01.wmf

2-5. Adjusting the Handle

The handle provides two viewing angles for bench-top use. To adjust its position, pull the ends out to a hard stop (about 1/4 inch on each side) and rotate it to one of the four stop positions shown in Figure 2-2. To remove the handle, adjust it to the vertical stop position and pull the ends all the way out.

2-6. Rack Mounting Kits

You can mount the 8842A in a standard 19-inch rack panel using the accessory rack mounting kits shown in Figure 2-3. To install the Single Rack Mount Kit, remove the handle and handle mounting plates, and attach the rack ears with the screws provided (Figure 2-4). The Dual Rack Mount Kit is installed similarly. (Both kits include mounting instructions.)

The rear feet may be rotated 180 degrees to clear a narrow rack space.

Operating Instructions

INSTALLATION

Figure 2-2. Adjusting the Handle

Figure 2-3. Rack-Mount Kits

f2-02.wmf

f2-03.wmf

2-3

8842A

Instruction Manual

Figure 2-4. Installing the Single Rack Mount Kit

2-7. OPERATING FEATURES

2-8. Power-Up Features

When the 8842A is turned on, all display segments light up for about 2 seconds while the instrument performs an internal self-test of its digital circuitry. The 8842A then assumes the following configuration:

• VDC function

• Autorange, starting in the 1000V range

• Slow reading rate

• Continuous, internal trigg er

• OFFSET off

• Local (front panel) control

While all display segments are lit during the power-up self-test, you can freeze the display by pressing the SRQ button. All display segments will then remain lit until you press any button.

f2-04.wmf

2-4

2-9. Front and Rear Panel Features

Front panel features are explained in Figure 2-5. Rear panel features are explained in Figure 2-6.

The alternate functions embossed below the front pane l range buttons and the spec ia l feature buttons are enabled by the CAL ENABLE switch. These functions are for use only when calibrating the instrument. See the Maintenance section for further explanation.

CAUTION

To avoid accidentally uncalibrating the 8842A, do not press the CAL ENABLE switch unless calibrating the instrument. Never cycle power on or off while the CAL ENABLE switch is on.

Operating Instructions

OPERATING FEATURES

Note that the VAC and mA AC functions are available only with the True RMS AC option. If this option is absent, pressing the VAC and mA AC function buttons causes the 8842A to briefly display an error message (ERROR 30).

FUNCTION BUTTONS:

Display

4-Wire Ohms DC Current AC Current*

CAL ENABLE switch enables calibration mode. (CAUTION! See text.)

HIGH and LO SENSE Terminals for 4-Wire Ohms Only

DC Volts AC Volts*

2-Wire Ohms

HI and LO

INPUT Terminals

2A INPUT Terminal

(Houses 2A fuse)

FRONT/REAR switch selects either front or rear inputs.

Calibration Functions

(embossed)

*Available with 8842A-09 True RMS AC only.

Gives error message if option not installed.

RANGE BUTTON:

20 mV or 20

200 mV or 200

2V or 2 k 20V or 20 k

SPECIAL FEATURES

200V, 200 k or 200 mA dc

1000V dc, 700V ac, 2 M or 2000 mA

20 M Autorange On/Off **

** For a description of the autorange feature, see paragraph 2-14.

POWER switch turns 8842A on or off. Also initiates power-up self-test and resets instrument to:

VDC function Autorange Slow reading rate Continuous trigger OFFSET off Local (front panel) control

Figure 2-5. Front Panel Features

f2-05_1.wmf

2-5

8842A

Instruction Manual

TRIG triggers a new reading. Enabled in external trigger mode.

OFFSET stores the displayed reading as an offset, which the 8842A subtracts from all subsequent readings in the function presently selected. Readings in the other functions remain unaffected. Pressing OFFSET again cancels the offset, or stores a new offset if in a different function.

Reading Rate Slow, Medium and Fast. Blinks off when a reading is triggered.

External Trigger Mode Enabled

Self-Test

Enabled

IEEE-488 Interface

Annunciators

Overrange

EXT TRIG toggles between internal and external trigger modes

RATE cycles between slow, medium and fast reading rates. Automatically selects the optimum filter for each reading rate.

SRQ generates a service request over the IEEE488 bus if enabled by the SRQ mask (IEEE-488 Interface option only). When pressed for 3 seconds, SRQ initiates diagnostic self-tests. NOTE: Leave inputs disconnected during selftests or the 8842A may indicate errors.

If the 8842A is in remote, LOCAL returns it to local control. If the 8842A is in local, the LOCAL button causes the 8842A to display its bus address for two and one half seconds. Ignored if the IEE-488 Interface is not installed.

Error Condition

Calibration Mode Enabled

Autorange On

Offset On

Function and Units Annunciators

2-6

Figure 2-5. Front Panel Features (cont)

f2-05_2.wmf

Operating Instructions

OPERATING FEATURES

EX TRIG input* TTL-level, falling-edge triggered (internally selectable)

IN OUT

EXT TRIG

10V MAX

JOHN FLUKE MFG. CO., INC. EVERETT, WA MADE IN U.S.A.

WARNING

GROUNDING CONDUCTOR IN POWER CORD MUST BE CONNECTED TO ENSURE PROTECTION FROM ELECTRICAL SHOCK

Rear feet rotate for rack mounting

SAMPLE COMPLETE output TTL-level. Normally high, pulsed low when samples for a reading are completed*

TALK ONLY and IEEE-488 ADDRESS Selection Switches*

TTL LEVELS

SHELL NOT GROUNDED

15V MAX

SAMPLE

COMPLETE

PATENTS PENDING

CAUTION

FOR FIRE PREVENTION REPLACE ONLY WITH 1/4 A SLOW FUSE, 100/120v 1/8 A SLOW FUSE, 220/240V

ADDRESS

TALK

ONLY

IEEE-05 AC-09

REMOVE GROUNDING SCREW BEFORE REMOVING COVER

Line V oltage Selection Switches

Serial Number

240V

LINE FUSE

250V

220V 120V 100V

LINE SET

Power-Line Fuse

IEEE STD-488 PORT

SH1, AH1, T5, L4, SR1, RL1,

DC1, DT1, PP0, C0, E1

20 VA 50/60/400 Hz

Power-Line Cord Connector

IEEE-488 Interface Bus Connector*

HIGH and LO SENSE Terminals for 4-Wire Ohms Only

INPUT SENSE

1000V

700V

1000V

700V

MAX

ALL

INPUTS

300V MAX

MAX

HI and LO INPUT Terminals

4 WIRE

*Available with IEEE-488 Interface only. Otherwise, the upper portion of the rear panel is covered with an insert as shown at right.

CAUTION: The rear panel insert is attached from inside the case. Refer to Section 8 for instructions on removing it.

JOHN FLUKE MFG. CO., INC. EVERETT, WA MADE IN U.S.A.

WARNING

GROUNDING CONDUCTOR IN POWER CORD MUST BE CONNECTED TO ENSURE PROTECTION FROM ELECTRICAL SHOCK

PATENTS PENDING

Rear Panel Insert

LINE FUSE

250V

240V 220V 120V 100V

20 VA 50/60/400 Hz

IEEE-05 AC-09

CAUTION

FOR FIRE PREVENTION REPLACE ONLY WITH 1/4 A SLOW FUSE, 100/120v 1/8 A SLOW FUSE, 220/240V

LINE SET

REMOVE GROUNDING SCREW BEFORE REMOVING COVER

Figure 2-6. Rear Panel Features

INPUT SENSE

1000V

MAX

700V

1000V

700V

ALL

INPUTS

4 WIRE

300V MAX

MAX

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8842A

Instruction Manual

2-10. Display Features

2-11. Error Messages

The 8842A features a vacuum fluorescent display with a numeric field and annunciators. The annunciators are explained in Figure 2-5.

If the 8842A detects an operator error or an internal failure, it displays an error message for about 2-1/2 seconds and then resumes normal operation. During this time, the front panel buttons are ignored. The error message consists of the ERROR annunciator and a two-digit error code. (See Figure 2-7.) Error codes are explained in Table 2-1.

If the FRONT/REAR switch is set to the REAR position while the mA DC or mA AC function is selected, ERROR 31 is displayed. In this case the error message is displayed until you return the switch to the FRONT position or select another function.

Figure 2-7. Typical Error Messages

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2-8

Operating Instructions

OPERATING FEATURES

Table 2-1. Error Codes

ERROR

CODE

ANALOG SELF-TEST ERRORS OPERATION ERRORS

1 200 VAC, Zero 30 AC funtions availible only with 8842A-09 True

2 700 VAC, Zero 31 mA AC or mA DC funtion selected while

3 mA AC, Zero 32

4 mA DC, Zero 40 Computed calibration constant out of

5 200 VDC, Zero 41 Calibration input out of acceptable range.

6 1000 VDC, Zero 42 Calibration memory write error. (Probably a

7 1000 VDC, Zero 50

8 20 VDC + 20MΩ 51 Calibration command not valid unless

9 20 VDC + 2000 kΩ 52 Command not valid at this time.

10 2 VDC + 2000 kΩ 53 Invalid calibration value in Put command.

11 200Ω, Overrange 54 Command not valid in calibration verification. 12 2 kΩ, Overrange 56 Variable inputs not allowed during A/D

13 20 kΩ, Overrange 60 Device-dependent commands not valid

14 200 kΩ, Overrange 71 Syntax error in device-dependent command

15 1000 VDC + X10 T/H + 20 MΩ 72 Guard crossing error detected by out Guard

16 200 VDC + 200 kΩ 73

17 200 VDC + 20 kΩ 77 IEEE-488 Interface self-test error.

DIGITAL SELF-TEST ERRORS

25 In-Guard µC Internal RAM 26 Display RAM 27 In-Guard µC Internal Program Memory 28 External Program Memory 29 Calibration Memory

NOTE: See the Maintenance section for a detailed description of self-tests.

MEANING ERROR CODE MEANING

RMS AC option.

REAR inputs selected. OFFSET selected with reading unavailible for

overrange.

range.(Previous cal may be wrong or there may be a hardware problem.)

Check that input is correct. (Previous cal may be wrong or there may be a hardware problem.)

hardware problem.) Guard crossing error detected by In-Guard

µC.

calibration mode is enabled.

(Example: Sending a negative value during ac calibration.)

calibration.Use prompted value.

during self-tests.

string.

µC. Guard crossing error detected at power on or

CAL ENABLE switch on at power on.

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Instruction Manual

2-12. Overrange Indication

2-13. Diagnostic Self-Tests

An input is overrange if it exceeds the full scale of the selected range. In most ranges, the 8842A indicates an input is overrange by lighting the OVER annunciator and showing a "1" on the display. (See Figure 2-8.) The sign, the position of the decimal point, and the other annunciators are not affected.

As a safety feature, the 8842A treats the 1000V dc and 700V ac rangesdifferently. In these ranges, the 8842A indicates when the input exceeds the input overload limit of 1000V dc or 700V ac, respectively, by lighting the OVER annunciator and flashing the display. Readings are still displayed.

The 8842A features diagnostic self-tests which check both the digital and analog circuitry in the instrument. The self-tests consist of 21 analog tests followed by the in-guard program memory, calibration memory, and display self-tests. To initiate the self-tests, press the SRQ button for 3 seconds. The instrument can be stopped in any of the test configurations by pressing the SRQ button while the test number is displayed. Press any button to continue the tests.

During the test, the TEST annunciator lights, and the numeric field displays the number of each analog test as it is performed. Then all display segments light up while the instrument performs the in-guard program memory, calibration memory, and display selftests. The 8842A then returns to the power-up configuration. The self-tests are described in greater detail in the Maintenance section.

The inputs must be left disconnected while the self-tests are performed or the 8842A may indicate that errors are present.

If the 8842A detects an error, it displays an error message for about 2-1/2 seconds. (Error codes 01 through 29 correspond to the self-tests.) If self-test errors are displayed even when the input terminals are disconnected, there may be a hardware problem in your 8842A. In that event, refer to the Maintenance section or contact your local Fluke representative.

2-14. Ranging

Measurement ranges can be selected using either autorange (by pressing the AUTO button) or manual range (by pressing another range button). The 8842A displays explicit units in every range, so that the display may be read directly.

2-15. AUTORANGE

In autorange, the 8842A goes to a higher range when the input exceeds full scale (199999 counts), and goes to a lower range when the input falls below 9% of full scale (18000 counts). While the instrument changes range , the numer ic field on the d isplay is b lank ed until a new reading is completed. However, the decimal point and units annunciators always indicate what range the instrument is in.

Pressing the AUTO button when the instrument is already in autorange toggles the 8842A from autorange to manual range. This causes the instrument to remain locked in the present range.

NOTE

2-10

The 8842A autoranges up to the highest ranges in all functions, down to the 200 mV range in the VDC and VAC functions, and down to the 200Ω range in the ohms functions. To select the 20 mV dc, 20Ω, or 200 mA dc range, press the respective range button (or send the respective range command, if using the IEEE-488 option).

2-16. MANUAL RANGE

In manual range, the 8842A remains fixed in the selected range until you select another range or press AUTO. If you select a range which is not valid for the present function, or select a function which is not valid for the present range, the 8842A selects the nearest valid range. For example, if the 8842A is in the VDC function and you press the 20 MΩ button, the 8842A selects the 1000V range.

The range buttons have no effect in the mA AC functions, since all measurements in these functions are made in the 2000 mA range.

2-17. Triggering

Triggering causes the 8842A to execute a measurement cycle and display the result. During each measurement cycle, the instrument samples the input a number of times and then averages the samples to compute a reading. The number of samples averaged for each reading depends upon the reading rate.

Each time a reading is triggered, the rate annunciator (S, M, or F) blinks off. In the fast reading rate, the F annunciator flashes so rapidly it appears to be almost constant.

How the 8842A is triggered depends on whether the continuous trigger mode or external trigger mode is selected. Pressing the EX TRIG (external trigger) button toggles the 8842A between the two modes.

Operating Instructions

OPERATING FEATURES

2-18. CONTINUOUS TRIGG ER MODE

In the continuous trigger mode, readings are triggered by a continuous, internal trigger. The rate of the trigger is set by the RATE button.

2-19. EXTERNAL TRIGGER MODE

In the external trigger mode, readings are triggered by pressing the TRIG button. If the IEEE-488 Interface option is installed, readings can also be triggered by remote commands or by using the rear panel external trigger (EXT TRIG) connector. (See the Options and Accessories section.)

In the external trigger mode, pressing any front panel button blanks the numeric field on the display until a new measurement is triggered. This ensures that all readings correspond to the instrument configuration indicated by the display annunciators. The blanking also occurs in the continuous trigger mode, but usually isn’t noticed because new measurements are triggered automatically.

The TRIG button does not trigger readings in the continuous trigger mode.However, it does blank the last reading to acknowledge a button was pressed.

2-20. Reading Rates and Noise Rejection

The RATE button allows you to optimize either measurement speed or noise rejection. The 8842A uses both analog and digital filtering to allow measurements in the presence of unwanted environmental noise (especially line-related noise). However, since filtering introduces a delay in response to a change in the input signal, there is an inherent tradeoff between noise rejection and measurement speed.

The instrument has three reading rates: slow (S) and medium (M), with a 5-1/2 digit display, and fast (F), with a 4-1/2 digit display. To provide optimum combinations of measurement speed and noise rejection, the RATE button allows control of both the internal trigger rate and the degree of filtering. The same degree of filtering is used in both the continuous and external trigger modes. In the 20 mV, 20Ω, and 200 mA dc ranges, use of slow (S) filter provides maximum noise rejection.

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8842A

Instruction Manual

2-21. Au tomatic Se ttling Time Delay

In the continuous trigger mode, the actual number of readings displayed per second for each reading rate is determined by the line-power frequency. At power-up, the 8842A senses the line-power frequency and adjusts the analog-to-digital converter timing characteristics for optimum normal-mode noise rejection. The resulting reading rates are shown in the specifications in Section 1.

When the external trigger mode is selected, the 8842A automatically inserts a delay after receiving a trigger signal, but before starting the first input sample. The delay is just long enough so that the reading will be correct (within a specified number of counts of the final value) even if the trigger signal occurs as the input makes a step change between zero and full scale (10,000 counts and full scale in the ac functions).The length of the delay depends on the range, function, and reading rate, as shown in the specifications in Section 1. The delay is enabled only in the external trigger mode. It can be turned off with a remote command over the IEEE-488 interface bus to accommodate special timing considerations.

Figure 2-8. Overrange Indication

2-22. External Trigger Input (Option -05 Only)

The rear panel EXT TRIG input is a TTL-level input which can be used to trigger measurements when the 8842A is in the external trigger mode. A measurement is triggered on the falling edge of the input. Since the EXT TRIG input is pulled high internally, it can also be controlled by a normally open switch. A measurement is triggered when the switch is closed. For special applications using the IEEE-488 Interface, the automatic setting time delay can be disabled using remote commands. (See Section 3.) Refer to Section 1 for timing details.

The polarity of the EXT TRIG input can be reversed by changing internal jumpers. Refer to the Maintenance section for instructions.

2-23. Sample Complete Output (Option -05 Only)

The SAMPLE COMPLETE output indicates when analog input sampling for a reading is completed. The output is a TTL-level signal which is pulsed low for approximately 2.5 µs when the input-sampling portion of the A/D conversion is completed. The signal is useful for interfacing with other equipment when the 8842A is used in external trigger mode in an instrumentation system. For example, the SAMPLE COMPLETE output could be used to advance a scanner to the next channel.

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2-12

2-24. MAKING MEASUREMENTS

2-25. Input Overload Protection Limits

WARNING

TO AVOID SHOCK HAZARD AND/OR INSTRUMENT DAMAGE, DO NOTAPPLY INPUT POTENTIALS THAT EXCEED THE INPUT OVERLOAD LIMITS SHOWN IN TABLE 2-2.

The 8842A is protected against input overloads up to the limits shown in Table 2-2. Exceeding these limits may damage the instrument and/or pose a shock hazard.

Table 2-2. Input Overload Limits

FUNTION CONNECTORS MAXIMUM INPUT

VDC INPUT HI and LO: 1000 dc MA DC 2A INPUTand INPUT LO: 2000mA 2 WIRE/4 WIRE kΩ INPUT HI and LO: 300V rms

Operating Instructions

MAKING MEASUREMENTS

SENSE HI and LO: 300V rms

VAC INPUT HI and LO: 700V rms, 1000V peak, or 2 x 10

V-Hz (whichever is less) MA AC 2A INPUT and INPUT LO: 2000 mA rms All Funtions Any terminal to earth: 1000V dc or peak ac

2-26. Measuring Voltage and Resistance

To measure voltage or resistance, select the desired function and connect the test leads as shown in Figure 2-9. Resistance can be measured in either the 2-wire or 4-wire configuration.

2-27. Measuring Current

To measure current, select the desired function and connect the test leads as follows:

1. Turn off power in the circuit to be measured (Figure 2-10).

2. Break the circuit (preferably on the ground side to minimize the common mode

voltage), and place the 8842A in series at that point.

3. Turn on power in the circuit, and read the display.

4. Turn off power in the circuit, and disconnect the 8842A.

2-28. Current Fuse Protection

The 2A input terminal is protected from overloads by a 2A, 250V fuse which is accessible from the front panel, and by an internal 3A, 600V fuse. If either fuse blows, the 8842A will respond as though the input were zero.

WARNING

TO AVOID ELECTRIC SHOCK, REMOVE THE TEST LEADS BEFOREREPLACING THE FRONT PANEL FUSE.

2-13

8842A

Instruction Manual

2-29. Offset Measurements

To replace the front panel fuse, first remove the test leads. Then press in the lip of the 2A input terminal slightly and rotate it 1/4-turn counterclockwise. Spring tension will force the fuse and fuse holder out of the front panel. The internal 3A fuse should be replaced only by qualified service personnel.

WARNING

WHEN THE OFFSET FEATURE IS IN USE, DISPLAYED READINGS ARE RELATIVE AND MAY NOT INDICATE THE PRESENCE OF DANGEROUS POTENTIALS AT THE INPUT CONNECTORS OR TEST LEADS. USE CAUTION TO AVOID ELECTRIC SHOCK OR INSTRUMENT DAMAGE.

The OFFSET feature allows you to store a reading as a relative reference value. When the OFFSET button is pressed, the 8842A stores the present reading and displays subsequent measurements as the difference between the measured value and the stored reading. The OFFSET annunciator is lit whenever an offset is in use.

The OFFSET feature may be used in all functions. Since the display represents a numeric difference, it always has a sign, even in the resistance and ac functions.

The offset can be canceled by pressing the OFFSET button again, in which case the OFFSET annunciator disappears from the display. The offset can also be canceled by storing an offset in another function. If a reading is overrange or unavailable when the OFFSET button is pressed, the 8842A indicates ERROR 32 and does not store the offset.

If you change functions while an offset is stored, the OFFSET annunciator disappears and the offset temporarily disappears. However, when you return to the original function, the offset is restored (and the OFFSET annunciator reappears) unless a new offset was established in another function. Note that the input overload limits are not changed by the use of the offset feature. However, the display flashes if the 8842A is in the 1000V dc or 700V ac ranges and the input exceeds 1000V dc or 700V ac, respectively.

While an offset is enabled, the 8842A indicates an overrange condition if either of the following conditions occur:

• The input signal is overrange

• The calculated reading is overrange

For example, suppose the instrument is in the 20V range of the VDC function and you store an offset of +15V. The maximum positive voltage reading that can be displayed without overranging is +4.9999V, which is actually a +19.9999V input signal. The maximum negative voltage reading that can be displayed without overranging is -

19.9999V, which is actually a -4.9999V input signal. You can measure a greater range of voltages by selecting a higher range.

2-14

When in autorange, the 8842A selects the range appropria te for the inpu t signa l, regardless of any stored offset. If, for example, a +10V offset is stored, and a +1V input is applied, the 8842A will autorange to the 2V range and display an overrange condition since it cannot display -9V on the 2V range. Manual range control could be used to lock the 8842A into the 20V range in this case.

Applications of the offset feature include correcting for test lead resistance in 2-wire resistance measurements, nulling offset currents or voltages, measuring voltage deviations, and matching resistors.

Operating Instructions

EXTERNAL CLEANING

Figure 2-9. Measuring Voltage and Resistance

Figure 2-10. Measuring Current

2-30. EXTERNAL CLEANING

WARNING

TO AVOID ELECTRIC SHOCK OR INSTRUMENT DAMAGE, NEVER GET WATER INSIDE THE CASE. TO AVOID INSTRUMENT DAMAGE, NEVER APPLY SOLVENTS TO THE INSTRUMENT.

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Should the 8842A case require cleaning, wipe the instrument with a cloth that is lightly dampened with water or a mild detergent solution.

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8842A

Instruction Manual

2-16

Chapter 3

Remote Programming

Title Page

3-1. INTRODUCTION................................................................................3-3

3-2. CAPABILITIES...................................................................................3-3

3-3. BUS SET-UP PROCEDURE...............................................................3-3

3-4. AN OVERVIEW OF REMOTE OPERATION...................................3-4

3-5. A NOTE ABOUT EXAMPLES...........................................................3-6

3-6. DEVICE-DEPENDENT COMMAND SET ........................................3-6

3-7. Bn (Offset Commands)....................................................................3-9

3-8. Cn (Calibration Commands)............................................................3-9

3-9. Dn (Display Commands)..................................................................3-9

3-10. Fn (Function Commands) ................................................................3-10

3-11. Get Commands.................................................................................3-10

3-12. G0 (Get Instrument Configuration)..................................................3-12

3-13. G1 (Get SRQ Mask).........................................................................3-12

3-14. G2 (Get Calibration Prompt)............................................................3-12

3-15. G3 (Get User-Defined Message)......................................................3-13

3-16. G4 (Get Calibration Status)..............................................................3-13

3-17. G5 (Get IAB Status).........................................................................3-14

3-18. G6 (Get YW Status).........................................................................3-14

3-19. G7 (Get Error Status).......................................................................3-14

3-20. G8 (Get Instrument Identification)...................................................3-15

3-21. N (Numeric Entry Command)..........................................................3-15

3-22. Put Commands.................................................................................3-15

3-23. P0 (Put Instrument Configuration)...................................................3-15

3-24. P1 (Put SRQ Mask)..........................................................................3-16

3-25. P2 (Put Calibration Value)..............................................................3-16

3-26. P3 (Put User-Defined Message)......................................................3-17

3-27. Rn (Range Commands)....................................................................3-17

3-28. Sn (Reading Rate Commands).........................................................3-17

3-29. Tn (Trigger Mode Commands)........................................................3-18

3-30. Wn (Terminator Commands)...........................................................3-19

3-31. X0 (Clear Error Register Command)...............................................3-19

3-32. Yn (Suffix Commands)....................................................................3-19

3-33. Z0 (Self-Test Command).................................................................3-19

3-34. (Device-Clear Command)................................................................3-20

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8842A

Instruction Manual

3-35. ? (Single-Trigger Command)...........................................................3-20

3-36. INPUT SYNTAX.................................................................................3-20

3-37. Definitions........................................................................................3-21

3-38. Input Processing...............................................................................3-21

3-39. Syntax Rules ....................................................................................3-23

3-40. OUTPUT DATA..................................................................................3-24

3-41. Loading Output Data........................................................................3-24

3-42. Types of Output Data.......................................................................3-25

3-43. Numeric Data and Error Messages...................................................3-25

3-44. MEASUREMENT DATA...........................................................3-25

3-45. OVERRANGE INDICATION ....................................................3-26

3-46. ERROR MESSAGES..................................................................3-26

3-47. Status Data .......................................................................................3-26

3-48. Output Priority .................................................................................3-26

3-49. SERVICE REQUESTS........................................................................3-27

3-50. The Serial Poll Register ...................................................................3-27

3-51. The SRQ Mask.................................................................................3-28

3-52. INTERFACE MESSAGES..................................................................3-29

3-53. Address Messages............................................................................3-29

3-54. Universal Commands.......................................................................3-29

3-55. Addressed Commands......................................................................3-30

3-56. TALK-ONLY MODE..........................................................................3-30

3-57. REMOTE CALIBRATION..................................................................3-31

3-58. TIMING CONSIDERATIONS............................................................3-31

3-59. IMMEDIATE MODE COMMANDS..................................................3-31

3-60. EXAMPLE PROGRAMS....................................................................3-32

3-2

This section contains programming instructions for use with the IEEE-488 Interface (Option -05). For installation instructions, refer to the Options and Accessories section.

3-1. INTRODUCTION

The IEEE-488 Interface turns the 8842A into a fully programmable instrument for use with the IEEE Standard 488-1978 interface bus (IEEE-488 bus). With the IEEE-488 Interface, the 8842A can become part of an automated instrumentation system. The 8842A can be under complete, interactive control from a remote bus controller; or it can be set to the talk-only mode, connected to a data logger or printer, and dedicated to a single task.

This manual assumes you know the basics of the IEEE-488 interface bus. For an introduction to the bus, request Fluke Application Bulletin AB-36, "IEEE Standard 4881978 Digital Interface for Programmable Instrumentation."

3-2. CAPABILITIES

The IEEE-488 Interface provides remote control of all front panel controls except for the POWER, CAL ENABLE, and FRONT/REAR switches. Other features include:

NOTE

Remote Programming

INTRODUCTION

• A simple and predictable command set

• Fast measurement throughput

• Full talk/listen capability, including talk-only operation

• Full serial poll capability, with bit-maskable SRQ

• Full remote/local capability, including local lockout

• EXTERNAL TRIGGER and SAMPLE COMPLETE connectors

• Remote calibration

• Programmable trigger sources, including two bus triggers

• Informative output suffix (suppressible)

• Selectable output termina tor s

The 8842A supports the following interface function subsets: SH1, AH1, T5, L4, SR1, RL1, DC1, DT1, E1, PP0, and C0.

3-3. BUS SET-UP PROCEDURE

To set up the 8842A on the IEEE-488 bus, proceed as follows:

1. Turn the 8842A POWER switch OFF and set the 8842A IEEE-488 address using the

rear panel IEEE-488 address switches shown in Figure 3-1.

2. With the 8842A POWER switch OFF, plug the IEEE-488 cable into the 8842A rear

panel IEEE-488 connector.

3. Switch on the 8842A.

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8842A

Instruction Manual

A D D R E S S

00 0 0 0000 11 001011 22 0 10110 01 0 0 0001 12 001100 23 0 10111

A5 A4 A3 A2 A1 A

T A L K

O N L Y

A5 A4 A3 A2 A1

A5 A4 A3 A2 A1 A

T A

R E

D D R E S S

T A L K

O N L Y

02 0 0 0010 13 001101 24 0 11000 03 0 0 0011 14 001110 25 0 11001 04 0 0 0100 15 001111 26 0 11010 05 0 0 0101 16 010000 27 0 11011 06 0 0 0110 17 010001 28 0 11100 07 0 0 0111 18 010010 29 0 11101 08 0 0 1000 19 010011 30 0 11110 09 0 0 1001 20 010100 31 Not allowed 10 0 0 1010 21 010101 1 XXXXXTALK

ONLY

Figure 3-1. IEEE-488 Address Selection

X = setting does not matter

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Whenever the 8842A is in the local state, the IEEE-488 address can be displayed on the front panel by pressing the LOCAL button.

3-4. AN OVERVIEW OF REMOTE OPERATION

An overview of remote operation is presented in the block diagram in Figure 3-2. Each block represents a register, buffer, etc., contained in the 8842A. The status registers in the center column indicate the instrument’s status, including its function, range, reading rate, etc. The input buffer receives data from the IEEE-488 bus. The output buffer receives data from the blocks to its left, and sends data on to the IEEE-488 bus.

3-4

Remote Programming

AN OVERVIEW OF REMOTE OPERATION

Figure 3-2. Remote Operation Block Diagram

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Instruction Manual

3-5. A NOTE ABOUT EXAMPLES

Information is transferred between blocks by device-dependent commands. Each command is shown next to an arrowhead which indicates the resulting information transfer. For example, Put command P0 takes a number from the input buffer and stores it in the primary status registers. Likewise, Get command G0 gets the content of the primary status registers and copies it into the output buffer.

In the examples in this manual, device-dependent commands are shown enclosed within quotation marks, as they would be entered in Fluke BASIC. For clarity, the commands are also separated by spaces. However, the spaces are are not necessary and may be omitted.

Example Explanation

"* F3 R1 S1 T2" This example is equivalent to "*F3R1S1T2" or

"*,F3,R1,S1,T2".

Using the Fluke 1722A Instrument Controller, these commands might be written into a BASIC program as shown in Figure 3-3. Examples using other controllers are given at the end of this section.

3-6

Figure 3-3. Typical Command String

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Examples of 8842A output data show the terminators CR and LF. The terminator EOI is not shown because it is a uniline message. However, the terminators CR, LF, and EOI are all selectable using the Write commands.

For reference, the ASCII and IEEE Std 488-1978 bus codes are shown at the back of this section.

3-6. DEVICE-DEPENDENT COMMAND SET

Device-dependent commands are the heart of 8842A remote control. They tell the 8842A how and when to make measurements, when to put data on the bus, when to make service requests, etc. Commands which correspond directly to the front panel controls or display are shown in Figure 3-4. The complete set of device-dependent commands is listed in Figure 3-5. The commands may be entered using either upper- or lower-case letters. See Table 6-15 for conditions under which certain commands are not valid.

Remote Programming

DEVICE-DEPENDENT COMMAND SET

TRIGGER COMMANDS ? Trigger Measurement

GET Trigger and Execute

TRIGGER MODE COMMANDS T0 Continuous Trigger

T1-T4 External Trigger

DISPLAY COMMANDS D0 Normal Display

D1 Blank Display

Sensed by G5

FUNCTION COMMANDS F1 VDC

F2 VAC F3 2 Wire kΩ F4 4 Wire kΩ F5 mA DC F6 mA AC

SUFFIX COMMANDS Y0 Disable Suffix

Y1 Enable Suffix

RANGE COMMANDS R0 Autorange On

R1 200 mV, 200Ω R2 2V, 2 kΩ R3 20V, 20 kΩ R4 200V, 200 kΩ, 200 mA R5 1000V dc, 700V ac,

2 MΩ, 2000 mA R6 20 MΩ R7 Autorange Off R8 20 mV, 20Ω

READING RATE COMMANDS

S0 Slow S1 Medium S2 Fast

SELF-TEST COMMANDS

Z0 Begins Self-Tests

GTL Go To Local

DEVICE-CLEAR COMMANDS

*Reset 8842A to power-up state

OFFSET COMMANDS B0 Offset Off

B1 Offset On

Figure 3-4. Commands Which Correspond to the Front Panel

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8842A

Instruction Manual

FUNCTON COMMANDS TERMINATOR COMMANDS

F1 VDC (Default) W0 E nabl e CR LF EOI (Def ault) F2 VAC W1 E nabl e CR LF Only F3 2 WIRE kΩ W2 E nabl e CR EOI Only F4 4 WIRE kΩ W3 E nabl e CR Only F5 M A DC W4 Enable LF EOI Only F6 M A AC W5 Enable LF Only

RANGE COMMANDS W7 Disable All Output Terminators R0 Autorange CLEAR COMMANDS R2 2V, 2 kΩ * Device Clear (Resets 8842A to def ault

R3 20V, 20 kΩ X0 Clear Error Register R5 1000V dc, 700V ac, 2 MΩ, 2000 mA SINGLE-TRIGGER COMMAND R6 20 mΩ ? Trigger Measurement R8 20mV, 20Ω GET COMMANDS READING RATE COMMANDS G0 Get Instrument Configuration (F,R, S, and

S0 Slow (Default) G1 Get SRQ Mask S1 Medium G2 Get Calibration Input Prompt S2 Fast G3 Get User-Defined Message

TRIGGER MODE COMMANDS G4 Get Calibration Status COMMAND TRIGGER

TO (Default) Internal Disabled - G6 Get YW Status (Suffix

T1 External Enabled On G7 Get Error Status T2 External Disabled On G8 Get Instrument Identification T3 External Enabled Off Note: G2 v al i d only in calibration mode. T4 External Disabled Of f PUT COMM ANDS Note: Delay is enabled by entering EX TRIG mode while in local. P0 Put Instrument Configuration (F,R,S,

OFFSET COMMANDS P1 Put SRQ Mask B0 P2 Put Variable Calibration Value B1 P3 Put User-Defined Message DISPLAY COMMANDS Note: P2 and P3 valid only in calibration

D0 Offset Off (Default) PUT COMMAND FORMAT D1 Offset On N <value> P0 SUFFIX COMMANDS N <value> P1 Y0 Normal Display (Default ) N < value> P2

Y1 Blank Display P3 < 16 ASCII characters>

MODE

REAR PANEL

TRIGGER

SETTLING

DELAY

conditions)

G5 Get IAB Status (input F/R, Autorange

On/Off, Offset On/Off)

Enabled/Disabled, Terminator Selection)

and T)

mode.

3-8

Figure 3-5. Device-Dependent Command Set

Device-dependent commands are device-dependent messages. For the 8842A to receive them, they must be sent over the IEEE-488 bus when the 8842A is in remote and has been addressed as a listener.

The following paragraphs describe the device-dependent commands in alphabetical order. Special characters (* and ?) are described last.

3-7. Bn (Offset Commands)

The Offset commands duplicate the function of the front panel OFFSET button. When the 8842A receives the B1 command, the 8842A stores the present reading as an offset for the present function. The B0 command cancels the offset. As with front panel operation, only one offset is allowed at a time.

The offset status (not the offset value) can be read using the G5 command. The 8842A defaults to B0 on both power-up and on any device-clear command (*, DCL, or SDC).

3-8. Cn (Calibration Commands)

The command string "C3 C0" erases the entire calibration memory. A complete calibration must then be performed.

CAUTION

Remote Programming

DEVICE-DEPENDENT COMMAND SET

The Calibration commands allow the 8842A to be calibrated under remote control. Commands C0, C1, and C2 duplicate the front panel calibration functions STORE, A/D, and HF AC, respectively. For a complete description of remote calibration, see the Maintenance section of this manual.

For the 8842A to accept these commands, the 8842A must be in the calibration mode (enabled by pressing the front panel CAL ENABLE switch). Otherwise, the commands generate an error message.

3-9. Dn (Display Commands)

The Display commands allow the user to blank the numeric field in the 8842A front panel display. The D0 command causes the display to operate normally, and is the default on power-up and upon any device-clear command (*, DCL, or SDC).

The D1 command blanks the numeric field in the display. The annunciators remain active, and all of the annunciators still flash if the input exceeds 1000V dc or 700V ac in the respective ranges. The D1 command is used for best performance when high IEEE488 Interface Data rates are required.

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3-10. Fn (Function Commands)

3-11. Get Commands

The function commands duplicate the front panel function buttons. The 8842A defaults to F1 on power-up and on any device-clear command (*, DCL, or SDC). If F0 is sent to the 8842A, it is internally converted to F1. The function setting can be read using the G0 command.

As with the front panel commands, selecting F6 automatically selects the 2000 mA range (R5). If the instrument is in range R8, commanding F5 automatically selects the 200 mA range (R4). If the instrument is in R1 through R6, commanding F5 automatically selects the 2000 mA range (R5). If the 8842A is in a resistance function (F3 or F4) and in R6, selecting any other function automatically selects R5. If the 8842A is in range R8 and F2 or F3 is commanded, range R1 is selected.

Example Explanation

"F3" Selects 2 WIRE kΩ function; it does not affect any other settings.

"* F6" Selects mA AC function and 2000 mA range. Resets all other settings to

default.

The Get commands "get" information from the 8842A for the cont ro lle r. Each Get command loads the output buffer with an output string in the format shown in Figure 3-6. Status data (the output from Get commands G0, G1, G3, G4, G5, G6, G7 and G8) is interpreted as shown in Table 3-1. The Get commands should not be confused with the interface message GET (Group Execute Trigger).

3-10

Figure 3-6. Output Data Format

f3-06.wmf

DEVICE-DEPENDENT COMMAND SET

Table 3-1. Status Data

OUTPUT

COMMAND

G0 Frst F = 1 – 6 as in Funtion commands (Fn)

G1 nn nn = 00 for SRQ disabled (default)

G3 aaaaaaaaaaaaaaaa 16 user-defined ASCII characters G4 10vm V = 0 Not in cal verification

STRING MEANING

9 for Self-Test r = 1 – 6 and 8 in Range commands (Rn) s = 0 – 2 as in Reading Rate commands (Sn) t = 0 – 4 as in Trigger Mode commands (Tn)

01 for SRQ on overrange 04 for SRQ on front panel SRQ 08 for SRQ on cal step complete 16 for SRQ on data availible 32 for SRQ on any error

Note: SRQ mask values may be added for combinations.Example: 33 for SRQ on overrange or any error.

1 Cal verifi cation

m = 0 Not in calibration mode

Remote Programming

1 A/D calibration 2 Offset and gain calibration 4 HF AC calibration

G5 1iab I = 0 FRONT inputs selected

1 REAR inputs selected

a = 0Autorange on

1 Autorange off (manual range)

b = 0 OFFSET off

1 OFFSET on

G6 10yw Y = 0 output suffix disabled

1 output suffix enabled

w = 0 – 7 as in Terminator commands (Wn) G7 10nn nn represents error code (See Table 2-1) G8

FLUKE, mmmmm,

0, Vn.n

Mmmmm = 8842A

Vn.n = IEEE-488 Interface software version number

The output data from some Get commands starts with a leading 1 or 10. This prevents the controller from suppressing leading zeroes and gives a uniform four-character length to all instrument configuration data (the data from Get commands G0, G4, G5, G6, and G7).

The Get commands are described further in the following paragraphs. For more information about output data, see paragraph 3-39.

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3-12. G0 (Get Instrument Configuration)

The G0 command copies the 8842A function, range, reading rate, and trigger mode into the output buffer in the format shown in Figure 3-6. The four digits returned represent the arguments for the equivalent F, R, S, and T commands, as shown in Table 3-1. An example output string follows.

Example Explanation

3410 CR LF 3: F3 (2 WIRE kΩ function)

4: R4 (200 kΩ range) 1: S1 (Medium reading rate) 0: T0 (Continuous trigger)

The second digit, which can vary from 1 to 6, indicates what measurement range the 8842A is in regardless of whether the 8842A is in autorange or manual range.

The output string from a G0 command is acceptable as an argument for an "N" command. This allows you to configure the 8842A from the front panel and then record the configuration over the bus for future use with a P0 command. However, 9mmm (meaning self-test) can not be used with the P0 command.

3-13. G1 (Get SRQ Mask)

The G1 command copies the present SRQ mask into the output buffer in the format shown in Figure 3-6. The SRQ mask values are explained in Table 3-1. An example output string follows. For more about the SRQ mask, see paragraph 3-47.

Example Explanation

33 CR LF Enable SRQ on any error or overrange

3-14. G2 (Get Calibration Prompt)

The G2 command is used when calibrating the 8842A under remote control. The command loads the output buffer with a calibration prompt that represents the input expected at the analog inputs. The calibration promp t is form atted as a sign ed decim a l with exponent, as shown in Figure 3-6. The suffix may be enabled with the Y1 command. Example output strings follow.

Examples Explanation

+1.00000E+0 CR LF Calibration prompt +190.000E-3 CR LF Calibration prompt +1.90000E+0, VDC CR LF Calibration prompt (Suffix enabled)

If an error has occurred, the G2 command loads the output buffer with an error message instead of the prompt. (See paragraph 3-39.)

The G2 command is valid only when the calibration mode is enabled by pressing the front panel CAL ENABLE switch. If the 8842A is not in the calibration mode, the G2 command generates an error message.

3-12

3-15. G3 (Get User-Defined Message)

The G3 command loads the output buffer with the user-defined message stored in calibration memory during the calibration procedure. The message consists of 16 ASCII characters, as shown in Figure 3-6.

The message is stored in calibration memory during calibration using the P3 command. If fewer than 16 characters have been stored, the remaining characters returned are spaces. If no message has ever been stored, a string of 16 null characters (hex 00) will be returned. Some example output strings follow.

Example Explanation

FL8842A.12-17-83 CR LF Identifies instrument and gives cal date. 01-25-84 CR LF Gives cal date. The last eight characters are

3-16. G4 (Get Calibration Status)

The G4 command is used when calibrating the 8842A under remote control. The command loads the output buffer with the instrument’s calibration status in the format shown in Figure 3-6. The status is represented by a four-digit integer which is interpreted in Table 3-1.

blank.

Remote Programming

DEVICE-DEPENDENT COMMAND SET

The first two digits are always 1 and 0. The third digit indicates whether or not the calibration verification mode is enabled. (This mode is enabled only when the calibration mode is enabled.) The fourth digit indicates whether or not the calibration mode is enabled, and if so, which part of the calibration procedure the 8842A is in. Example output strings follow.

Example Explanation

1000 CR LF 1: Leading 1

0: Leading 0 0: Not in cal verification 0: Cal mode disabled

1001 CR LF 1: Leading 1

0: Leading 0 0: Not in cal verification 1: Cal mode enabled; A/D cal selected

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3-17. G5 (Get IAB Status)

3-18. G6 (Get YW Status)

The G5 command loads the output buffer with the IAB status in the format shown in Figure 3-6. As Table 3-1 explains, the IAB status is a four-character string which indicates the status of the FRONT/REAR switch (front or rear analog inputs selected), the autorange feature (autorange on or off), and the OFFSET feature (OFFSET on or off). The first digit is always 1. An example output string follows.

Example Explanation

1011 CR LF 1: Leading 1

0: FRONT inputs 1: Autorange off 1: OFFSET feature on

It is useful to know whether autorange is on or off because this information is not available from the G0 command. For example, the G0 command could indicate that the 8842A was in the 200 mV range, but it would not indicate whether the 8842A was in autorange or manual range.

The G6 command loads the output buffer with the YW status in the format shown in Figure 3-6. The YW status is a four-character string which indicates which terminators are selected and whether the output suffix is enabled or disabled, as shown in Table 3-1. The first two digits are always 1 and 0. An example output string follows.

Example Explanation

1015 LF CR 1: Leading 1

0: Leading 0 1: Y1 (enable output suffix) 5: W5 (enable LF only)

3-19. G7 (Get Error Status)

The G7 command copies the error status register into the output buffer in the format shown in Figure 3-6. The first two digits are always 1 and 0. The second two digits represent the appropriate error code, if an error has occurred. (Error codes are listed in Table 2-1, Section 2). If an error has not occurred, the second two digits are 00. An example output string follows.

Example Explanation

1071 CR LF 1: Leading 1

0: Leading 0 71: Syntax error in device-dependent command string

The G7 command gives the error status as it exists when the command is executed at its position in the input string. The G7 command does not clear the error status register. For more information about error messages, see paragraph 3-40.

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3-20. G8 (Get Instrument Identification)

The G8 command copies the 8842A instrument identification into the output buffer in the format shown in Figure 3-6. The identification is represented by four comma separated fields that are interpreted in Table 3-1.

The first field indicates the manufacturer, the second indicates the instrument model number, the third is always zero, and the fourth indicates the version number of the IEEE-488 interface software.

Example Explanation

FLUKE,8842A,0,V4.0 CR LF This instrument is a Fluke 8842A with IEEE488 interface software version 4.0.

3-21. N (Numeric Entry Command)

Format Explanation

N<numeric entry> Where <numeric entry> is one of the following:

Remote Programming

DEVICE-DEPENDENT COMMAND SET

Example Explanation

"N12001" Enters the five-digit integer 12001 "N-1.23E2" Enters -1.23 x 10 "N+154.33E-1" Enters 1.5433 x 10

The N command enters numeric values for use with subsequent Put commands. The interpretation of the numeric value depends on which Put command it is used with.

The E can be used within an N command for entering an exponent of 10. The N can be used without an E, but an E requires a prior N. The exponent can be any integer from -9 to +9.

The mantissa may exceed 5-1/2 digits. The 8842A accurately calculates the appropriate exponent and then disregards all but the first 5-1/2 digits of the mantissa. However, a syntax error will occur if the numeric entry overflows the input buffer.

Example Explanation

"N123456789" Enters +1.23456 x 10

3-22. Put Commands

The Put commands P0 through P3 set up the 8842A’s configuration and operating modes by entering ("putting") information in the appropriate registers. The put commands are described further in the following paragraphs.

3-23. P0 (Put Instrument Configuration)

Format Explanation

N<frst>P0 Where <frst> is a four-digit integer interpreted as arguments for the F,

R, S, and T commands.

Example Explanation

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3-24. P1 (Put SRQ Mask)

"N3120 P0" Identical to F3 R1 S2 T0. Selects 2 WIRE kΩ function, 200Ω range,

fast sample rate, continuous trigger.

The P0 command allows broadside loading of the Function, Range, Reading Rate, and Trigger Mode commands (F, R, S, and T). The codes for these commands are listed in Figure 3-5.

A numeric entry for P0 must be within +1000 and +6824. Each of the four digits must not exceed its maximum allowed value (6, 8, 2, and 4, respectively) or an error message will occur and the instrument configuration will remain unchanged. The entry may be expressed as an integer, real number, or real number with exponent, as described under the N command. Any fractional part is ignored.

Example Explanation

"N3112 P0" Sets the 8842A to F3, R1, S1, and T2.

Format Explanation

N<SRQ mask>P1 Where <SRQ mask> is a two-digit integer from 00 to 63.

The P1 command is used to program the 8842A to make service requests on userspecified conditions. The two-digit code for the SRQ mask is interpreted in Table 3-1 under the G1 command. For more about the SRQ mask, see paragraph 3-51.

Numeric entries for the P1 command must be between 0 and +63 (inclusive), or an error will occur and the SRQ mask will remain unchanged. The entry may be expressed as an integer, real number, or real number with exponent, as described under the N command. Any fractional part is ignored.

Example Explanation

"N0.17E+2 P1" Sets SRQ mask to 17. Enables SRQ on data available or overrange.

"N1 P1" Sets SRQ mask to 01. (A leading zero is assumed.) Enables SRQ on

overrange.

3-25. P2 (Put Calibration Value)

Format Explanation

N<value>P2 Where <value> can be an integer, real number, or real number with

exponent, as described under the N command.

Example Explanation

"N1 P2" If the 8842A is in VDC, the next calibration input expected is

1.00000V dc.

The P2 command is used to enter variable input calibration values just like the front panel VAR IN button. To accept the P2 command, the 8842A must be in the calibration mode (enabled by pressing the front panel CAL ENABLE switch). Otherwise, the P2 command will generate an error message.

3-16

The variable input is a measurement value that is to be used as the calibration value for the next calibration step. Its format is the same as a measurement value. But since it is coming from the controller, the value can be specified using any valid format (signed interger, real number, or real number with exponent). For example, if the 8842A prompts for an input value of 100Ω for the next calibration step, but the available source is

98.97Ω, the variable input can be specified as "N+9.897E+1", "N0.9897E2", N9897E-2",

etc. All of these strings result in the same value being used for the next calibration step. For complete information about remote calibration, refer to the Maintenance section.

Numeric values exceeding full scale and negative values for ohms and AC generate error messages.

3-26. P3 (Put User-Defined Message)

Format Explanation

P3<value> Where <value> is a string of up to 16 ASCII characters.

Example Explanation

"P3FL.8842.12-17-83" Loads the message "FL.8842.12-17-83" into calibration

memory.

"P3HIMOM" Loads the message "HIMOM" into calibration memory. The

remaining eleven characters are assumed to be blank.

The P3 command stores a user-defined message in the internal calibration memory during remote calibration. The message may be read with a subsequent G3 command.

The message may consist of up to 16 ASCII characters, and typically represents the instrument’s identification, calibration date, calibration facility, etc. If fewer than 16 characters are specified, spaces are appended to fill the message to 16 characters. Spaces and commas in the 16-character input string are suppressed. Lower-case letters are converted to upper-case.

Remote Programming

DEVICE-DEPENDENT COMMAND SET

If fewer than 16 characters are specified, the P3 command must not be followed by other commands in the same input command string. Otherwise, the subsequent commands will be misinterpreted as part of the 16-character string.

To accept the P3 command, the 8842A must be in the calibration mode (enabled by pressing the front panel CAL ENABLE switch). Otherwise, the P3 command will generate an error message.

3-27. Rn (Range Commands)

The Range commands duplicate the front panel range buttons. For example, R0 selects autorange, and R3 selects the 20V/20 kQ range.

The R7 command turns autorange off, just as the AUTO button does when it is toggled. Command R7 puts the 8842A into manual range, selecting whatever range the instrument is in when the command is received.

The 8842A defaults to R0 on power-up and any device-clear command (*, DCL, or SDC). The range setting can be read using the G0 command.

3-28. Sn (Reading Rate Commands)

The Reading Rate commands duplicate the front panel RATE button. Like the RATE button, the reading rate command also selects the number of digits displayed and the filter setting. (Filter settings are shown in the specifications in Section 1).

NOTE

The 8842A defaults to S0 on power-up and any device-clear command (*, DCL, or SDC). The reading rate can be read using the G0 command.

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3-29. Tn (Trigger Mode Commands)

The Trigger Mode commands duplicate the front panel EX TRIG button. In addition, the commands can enable or disable the rear panel trigger and the automatic settling time delay.

Figure 3-7 illustrates how to select among the five types of triggers: continuous trigger, front panel trigger, rear panel trigger, and two bus triggers. Note that the front panel TRIG button is enabled only while the instrument is under local control.

3-18

Figure 3-6. Trigger Selection Logic Diagram

f3-07.wmf

In the continuous trigger mode (T0), triggers are initiated at the selected reading rate. Each new reading is loaded into the output buffer as it becomes available, unless the instrument is busy sending previous output data.

The trigger mode can be read using the G0 command. The 8842A defaults to T0 on both power-up and any device-clear command (*, DCL, or SDC).

3-30. Wn (Terminator Commands)

The Terminator commands select what terminators the 8842A appends to every output string. The available terminators are: Carriage Return (CR), Line Feed (LF), and End Or Identify (EOI).

CR and LF are ASCII control codes, sent over the data lines just like output data. EOI is a uniline message which is sent simultaneously with the last character in the output string. Normally, each output string is terminated with CR followed by LF and EOI.

The terminator selection can be read using the G6 command. The 8842A defaults to W0 on power-up and any device-clear command.

3-31. X0 (Clear Error Register Command)

The X0 command clears the 8842A’s error status register. After an X0 command is executed, a G7 command (Get Error Status) would return 1000 (no errors).

Note that the error status register is also cleared when any device-clear command (*, DCL, or SDC) is executed. However, X0 is useful for clearing the error status register without forcing a complete instrument clear (as do the device-clear commands).

Remote Programming

DEVICE-DEPENDENT COMMAND SET

3-32. Yn (Suffix Commands)

The Suffix commands enable or disable a suffix which the 8842A can append to all numeric data (the data in response to G2 or trigger commands). The suffix includes a comma, an overrange indicator (>), and a function indicator (VDC, VAC, OHM, IDC, or IAC). The suffix is illustrated in Figure 3-6. An example of suffixed data is given in paragraph 3-43.

To read suffixed data with a controller using BASIC, one can read the whole line into a string variable and then convert the numeric part into a numeric variable. However, it is much easier to read the numeric part directly into a numeric variable and the suffix into a string variable. The leading comma of the suffix serves as a convenient delimiter. For example, a BASIC program statement might be:

INPUT @1,A, B$

The suffix status can be read using the G6 command. The 8842A defaults to Y0 on power-up and any device-clear command (*, DCL or SDC), unless in talk-only mode.

3-33. Z0 (Self-Test Command)

The Z0 command initiates the diagnostic self-tests as does pressing the front panel SRQ button for 3 seconds. The 8842A then runs through the tests in sequence. (For a description of the self-tests, see the Maintenance section.)

If the 8842A detects an error, an error message is loaded into the output buffer and displayed on the front panel. After the last test, the 8842A is reset to the p ower -up configuration, and it begins taking readings.

It is an error to send the 8842A device-dependent commands dur ing the sel f-te s ts. However, the controller can still make the 8842A a talker to read the output buffer during the test, and thus record each error that occurs, except that only the last of the digital selftest errors can be read. After the tests, only the last error is stored in the output buffer if more than one error occurred.

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3-34. (Device-Clear Command)

Error messages are indicated by an exponent of +21. For more about error messages, see paragraph 3-40.

Since the 8842A is reset at the end of the self-tests, the Z0 command should be the last command in a given command string. The 8842A will ignore any subsequent commands in the same command string.

When the self-tests are complete and no errors have occurred, the serial poll register will have bit 5 (Data Available) true and bit 6 (Any Error) false. See paragraph 3-50 for more about the serial poll register.

The asterisk command (*) is a device-dependent message which resets the 8842A to the power-up default settings and clears all registers and buffers except for the input buffer. The remote/local status remains unchanged. The asterisk command performs the following:

1. Implements the default settings F1, R0, S0, T0, D0, B0, Y0, W0.

2. Clears the error status register (equivalent to X0).

3. Zeros the SRQ mask, prohibiting service requests (equivalent to N0 P1).

4. Zeros the numeric entry register (equivalent to N0).

5. Zeros the serial poll register.

6. Sets the SRQ line false. The asterisk command is executed in its proper turn in a string, just like any other

command, without affecting the contents of the input buffer. All commands which precede the asterisk command are performed.

The asterisk command is useful to ensure that the 8842A is initialized to the same state each time a program is run. By contrast, the similar interface messages DCL (Device Clear) and SDC (Selected Device Clear) cause the entire input buffer to be cleared immediately.

DCL, SDC, and the asterisk command are all considered to be device-clear commands because the results are so similar; however, DCL and SDC are not identical to the asterisk command described here. DCL and SDC are discussed further in the paragraph on interface messages.

3-35. ? (Single-Trigger Command)

The Single-Trigger command (?) causes the 8842A to take a reading and place the result into the output buffer. To accept this command, the 8842A must be in external trigger mode (selected by the T1, T2, T3, or T4 command).

The Single-Trigger command is one of five ways to trigger a reading. (See Figure 3-7.) Of these, only the Single-Trigger command (?) and the Group Execute Trigger command (GET) are loaded into the input buffer.

3-20

3-36. INPUT SYNTAX

The following paragraphs describe how to construct groups of commands for the 8842A. A few definitions are presented first, followed by a description of how the 8842A processes input commands. Guidelines are then summarized in four syntax rules.

3-37. Definitions

• Output commands: Commands which load data into the output buffer. The output

commands are: the Get commands (G0 through G8); the Single-Trigger Command (?); the Continuous Trigger command (T0); and Group Execute Trigger (GET), not to be confused with the Get commands.

• Input terminator: An ASCII control code sent by the controller which tells the 8842A

to execute all device-dependent commands since the previous terminator. Terminators are CR (Carriage Return), LF (Line Feed), EOI (End Or Identify), and GET (Group Execute Trigger).

• Input command string: One or more device-dependent commands followed by a

terminator.

3-38. Input Processing

When the 8842A receives commands from the bus, it stores the m in a 31-charac ter inpu t buffer as a continuous string of characters. Commands in the input buffer are not executed or checked for syntax until an input terminator is received or the input buffer becomes full. The only valid input terminators are CR, LF, GET (Group Execute Trigger), and/or EOI.

Remote Programming

INPUT SYNTAX

When the 8842A receives an input terminator, it executes the previous commands in the order in which they were received. As input characters are processed and executed, space is made available in the input buffer for new characters.

If the input buffer becomes full, the 8842A stops accepting characters from the bus until all complete command strings currently in the input buffer have been executed. In this way, characters sent to the 8842A are never lost due to buffer overflow.

In some instances, a terminator is automatically transmitted at the end of the controller’s output string. For example, in Fluke BASIC, the PRINT statement always finishes with a CR LF pair. If a controller does not have this feature, the programmer must transmit a terminator explicitly.

The 8842A accepts alphabetic characters in either upper or lower case. Spaces, commas, and control codes are ignored and are not placed in the input buffer. If the 8842A receives a group of terminators (such as CR LF or CR LF EOI), only a single terminator is loaded into the input buffer. Numeric values used in PUT commands may be in NR1, NR2, or NR3 format as described in the IEEE-488 Codes and Formats Recommended Practice. (These correspond to the signed integer, real number, and real-number-withexponent formats described under the N command.) For reference, Figure 3-8 shows how the 8842A interprets messages.

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DEVICE-DEPENDENT MESSAGES

Single-character Commands

Bn Cn Dn Fn Gn Pn Rn Sn Wn Xn Yn Zn Each of these commands requires the single

Numeric-entry Characters

NE. + - 0123456789 These characters are used for entering numbers

Terminators

CR Carriage Return LF Line Feed GET Group Execute Trigger EOI End Or Idenity (used as END/DAB)

INTERFACE MESSAGES Address Messages

MLA My Listen Address MTA My Talk address UNL Unlisten UNT Untalk

Universal Commands

ATN Attention DCL Device Clear IFC Interface Clear LLO Local Lockout REN Remote Enable SPD Serial Poll Disable SPE Serial Poll Enable

Addressed Commands

GET Group Execute Trigger GTL Go to Local SDC Selected Device Clear

Ignored Characters

, comma These characters may be inserted anywhere in a

Space Character string without affecting the string. All Other ASCII non-printing characters (except CR

and LF)

ERROR-PRODUCING CHARACTERS

! “ # $ ‘ ( ) / : < = > ; @ [ / ]  ~ HIJKLMOQUV

numeric digit (n).

character string without affecting the string.

They carry no special meaning and are ignored by the 8842A. They are not placed in the input buffer.

The error annunciator is displayed on the 8842A front panel when one of these characters is encountered (ERROR 71).

Figure 3-7. Interpretation of Messages

3-22

Illegal commands (e.g., F9) generate an error message, but are otherwise ignored, and do not affect the instrument’s configuration.

Example Explanation

"* F9" This would load the output buffer with an error message and select F1

(established by the * command).

3-39. Syntax Rules

Four syntax rules should be followed when constructing input command strings. They are:

• RULE 1: Read output data only once.

To prevent old (previously read) data from being read a second time by mistake, the output buffer is always cleared after it has been read. If the output buffer is read twice without an intervening output com mand, the 8842A will not respond to the second attempt to read the output buffer. (However, if the 8842A is in T0, no intervening command is necessary.)

• RULE 2: Use no more than one output command per input command string.

Because the 8842A has only one output buffer, it writes new data over old. If an input command string contains more than one output command, only the data from the last command can be read.

Remote Programming

INPUT SYNTAX

Example Explanation

"F1 T3 ? F2 ?" Improper construction. The second trigger writes over the first. To

obtain two readings, send two complete command strings (separated by

terminators). "F2 R3 S0 T3 ?" Correct construction. The string contains only one output command. "F2 R3 S0" Correct construction. It is permissible for a string not to contain an

output command.

• RULE 3: Read the output data generated by one input command string

the next input command string. Output data remains available in the output buffer until it is read, or until the next input command string is received. As soon as the controller finishes reading the output buffer, or as soon as the 8842A receives a new input terminator, the Data Available bit in the serial poll register is set false. When this bit is false, data can no longer be read from the output buffer. Therefore, an output string which is available must be read by the controller before, rather than after, the next input command string is sent.

Rule 3 is most evident in the external trigger mode, and is best demonstrated by a programming example. The following program is written first incorrectly, and then correctly, in Fluke BASIC using the 1722A Instrument Controller.

Incorrect example

100 PRINT @3, "T1 ?" 200 PRINT @3, "F4" 300 INPUT @3, A

before sending

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In this incorrect example, the INP UT state me nt is loca ted inc or rec tly for reading the measurement data from line 100. The new input command string "F4" disallows the reading of data from the output buffer.

Correct example

100 PRINT @3, "T1 ?" 200 INPUT @3, A 300 PRINT @3, "F4"

In this example, the reading taken at line 100 is read at line 200. Then the F4 command is sent. Note that in the external trigger mode, the reading from line 100 flashes on the 8842A display too briefly to see. This is because the function change at line 300 blanks the display until the next trigger.

The previous example could also be correctly programmed as follows:

100 PRINT @3, "T1 ? F4" 200 INPUT @3, A

• RULE 4: If an input command string contains a trigger, enter the commands in the

following order:

a. Commands to configure the instrument (if any). b. The trigger command. c. Commands to re-configure the instrument (if any). d. Terminator(s).

The principle behind this rule is that the 8842A executes all commands in the exact order they are received, from left to right as written.

Example Explanation

"F3 F4 ?" Improper construction. F3 is effectively discarded. "F3 ? F4" Correct construction. The 8842A is configured in F3, and the trigger is

executed. Then the 8842A is left in F4.

3-40. OUTPUT DATA

The following paragraphs describe the data that can be loaded into the 8842A output buffer and sent to the IEEE-488 bus. The paragraphs describe how and when data is loaded into the output buffer, the types of output data, and their relative priority.

Note that the 8842A can also send data to the IEEE-488 bus from the serial poll register. For a description of this data, see paragraph 3-47.

3-41. Loading Output Data

The output buffer is loaded when the 8842A receives an output command, or when an error occurs. Output commands are those device-dependent commands which load the output buffer with data:

3-24

• Get commands (G0 through G8)

• Single-trigger command (?)

• Group execute trigger (GET)

• Continuous Trigger (T0)

Because the 8842A gives priority to input processing, it completely processes all characters in the input buffer before it loads the output buffer. When the output buffer is loaded, the Data Available bit in the serial poll register is set true.

Data from the output buffer is not actually loaded onto the IEEE-488 bus until the controller addresses the 8842A as a talker. This is done by sending the interface message MTA (My Talk Address).

3-42. Types of Output Data

The types of data that can be loaded into the output buffer are shown in Figure 3-6. Each type has its own format. Error messages, which are loaded into the output buffer if an error occurs, are formatted as numeric data.

3-43. Numeric Data and Error Messages

Numeric data is loaded into the output buffer in response to the G2 command or an instrument trigger, and has the format shown in Table 3-2. The exponent is always a multiple of 3, as in engineering notation. The position of the decimal point matches the front panel display.

Numeric data is of constant length, It is 11 characters (plus terminators) when the suffix is disabled, and 16 characters (plus terminators) when the suffix is enabled.

Remote Programming

OUTPUT DATA

The suffix is enabled by the Y1 command, and consists of five ASCII characters as shown in Figure 3-6. The suffix is appended only to numeric data, never to status data. The terminators are determined by the Terminator commands. The default is CR LF EOI.

There are three types of numeric data: measurem ent data , overr ange ind ica tion, an d error messages.

3-44. MEASUREMENT DATA

Measurement data has the numeric data format shown in Table 3-2, and is always in the units of volts, amps, or ohms.

Table 3-2. Numeric Output Data Format

RANGE

VDC, VAC 2-, 4-WIRE kΩ MA DC, mA AC

R8 ±1x.xxxxE-3* ±1x.xxxxE+0** -- ±9.99999E+9 +1.00xxE+21 R1 ±1xx.xxxE-3 ±1xx.xxxE+0 -- ±9.99999E+9 +1.00xxE+21 R2 ±1.xxxxxE+0 ±1.xxxxxE+3 -- ±9.99999E+9 +1.00xxE+21 R3 ±1x.xxxxE+0 ±1x.xxxxE+3 -- ±9.99999E+9 +1.00xxE+21 R4 ±1xx.xxxE+0 ±1xx.xxxE+3 ±1xx.xxxE-3*** ±9.99999E+9 +1.00xxE+21

MEASUREMENT DATA

OVERRANGE

INDICATION

MESSAGES

ERROR

R5 ±1xxx.xxE+0 ±1xxx.xxE+3 ±1xxx.xxE-3 ±9.99999E+9 +1.00xxE+21

R6 -- ±1x.xxxxE+6 -- ±9.99999E+9 +1.00xxE+21 * VDC only ** 4-wire ohms *** mA DC only

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Instruction Manual

3-45. OVERRANGE INDICATION

3-46. ERROR MESSAGES

NOTE

In the fast (F) reading rate, the least significant digit is always zero, and should be disregarded when interpreting accuracy specifications.

If a reading is overrange (≥ 200,000 counts), the measurement data has the following format:

±9.99999E+9 <suffix> <terminators>

Overvoltage readings (> 1000V dc or 700V ac) do not result in this display.

If the 8842A detects an error, it loads an error message into the output buffer in the following numeric format:

+1.00xxE+21 <terminators>

The digits xx represent a two-digit error code. (Error codes are listed in Table 2-1, Section 2.) The suffix is always suppressed for error messages.

Example Explanation

+1.0071E+21 CR LF ERROR 71: Syntax error in device-dependent command string.

As with local operation, none of the errors are latching except for ERROR 31. If the mA DC or mA AC function is requested while the FRONT/REAR switch is in the REAR position, ERROR 31 will persist until the switch is set to FRONT or another function is selected.

To check for an error condition, test whether the output buffer data is greater than or equal to +1E+21, or test the Any Error bit (bit 6) in the serial poll register.

3-47. Status Data

Status data is the output in response to G0, G1, G3, G4, G5, G6, G7 and G8, commands. The data is formatted as shown in Figure 3-2, and is interpreted in Table 3-1. Examples of status data can be found in the description of the Get commands.

The user-defined message loaded by the G3 command consists of 16 characters plus terminators. The SRQ mask loaded by the G1 command consists of two integers plus terminators. All other status data is always a four-digit integer plus terminators. The terminators LF (Line Feed) and CR (Carriage Return) each add an extra character when enabled.

The 8842A begins some status data with a leading ASCII one (1) or a one and a zero (10). This prevents the controller from suppressing any leading zeros present in the 8842A’s output string. It also gives a uniform four-character length to all instrument configuration data.

Status data from the Get commands reflects the status of the 8842A at the time the command is executed at its place in the input command string.

3-26

3-48. Output Priority

Since only one output string is allowed per input command string, the 8842A gives priority to some types of data over others. An input command string may call for more than one output string. (For example, an input string may contain a Get command but also cause an error message.) However, the output buffer is loaded with only one output string. That string is selected according to the following priority:

1. Status data (from G0, G1, G3, G4, G5, G6, G7 and G8)

2. Error messages (if an error exists)

3. Numeric data (from G2 or a trigger) This means that an error message always overrides numeric data, but status data is sent

even in the presence of an error. However, the status data does not clear the error message; the error message is sent the next time numeric data is requested.

3-49. SERVICE REQUESTS

Service requests let bus instrumen ts get the attention of the system controller. The requests are sent over the SRQ line (one of the IEEE-488 bus lines). If more than one instrument on the bus is capable of sending service requests, the controller can learn which one made the request by taking a serial poll. Each device (including the 8842A) responds to the poll by sending the contents of its serial poll register. The serial poll register indicates whether or not the device requested service, and if so, the reason for the request.

The 8842A may be programmed to make a service request on user-specified conditions. The conditions are specified by entering a value for the service request mask (SRQ mask) with the P1 command. The SRQ mask works by monitoring the serial poll register, which in turn monitors various conditions in the 8842A.

Remote Programming

SERVICE REQUESTS

3-50. The Serial Poll Register

The serial poll register is a binary-encoded register which contains eight bits, as illustrated in Figure 3-9. The controller can read the 8842A serial poll register at any time by taking a serial poll. Because serial poll register data is loaded directly onto the bus (instead of being loaded into the output buffer first), reading the serial poll register leaves data in the output buffer intact.

Service requests may also be initiated using the front panel SRQ button if it has been enabled by the SRQ mask.

The eight bits of the serial poll register are described in Figure 3-9. Note that the SRQ mask uses bits 1 through 6 to set bit 7 (the RQS bit). When the RQS bit is set true, the 8842A sets the SRQ line true, which generates a service request. A bit is considered true when it is set to 1.

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Instruction Manual

BIT: 8 7 6 5 4 3 2 1

0 RQS ANY

ERROR

DECIMAL

VALUE:

Bit Name Set Cleared

1 Overrange An overrange condition occurs Device command received, or

2 Not used Never Always 3 Front panel SRQ Front panel SRQ button

4 Cal Step Complete Completion of store command

5 Data Availible Output buffer loaded with any

6 Any Error An error condition occurs. At

64 32 16 8 4 2 1

DATA

AVAILIBLE

pressed

(C0)

data (Readings, Error Messages. Get Responses)

the same time the output buffer is loaded with an error message. This sets bit 5.

CAL STEP

COMPLETE

FRONT

PANEL SRQ

Bus or Rear Panel Trigger, or Output buffer is read

Device command received

Device command received, or Bus or Rear Panel Trigger, or Output buffer is read

Device command received, or Output buffer is read

0 OVER-

RANGE

7 RQS Any SRQ mask-enabled bit is

set.

8 Not used Never Always

Figure 3-8. Serial Poll Register

For example, the serial poll register reads 00010000 (binary) when data is available. This value is read in binary by the controller, which might numerically reformat the value to 16 (decimal) or 10 (hexadecimal).

The serial poll register is cleared whenever the 8842A receives a new input command string.

3-51. The SRQ Mask

The SRQ mask is a two-digit integer that specifies which conditions will generate a service request. The SRQ mask is entered using the P1 command and can be read with the G1 command. The conditions corresponding to each SRQ mask value are listed under G1 in Table 3-1.

All SRQ mask-enabled bits are cleared

3-28

Remote Programming

INTERFACE MESSAGES

The SRQ mask can enable any combination of serial poll register bits 1 through 6. Its sixbit binary representation is ANDed bit-for-bit with serial poll register bits 1 through 6 whenever the output buffer is loaded. If any mask-enabled bit in the serial poll register comes true, the RQS bit (bit 7) is set true, generating a service request.

Example Explanation

"* N4 P1 ?" An SRQ is generated if the front panel SRQ button is pressed. The string

sets the SRQ mask to 04, which is 000100 in binary. This mask is ANDed with the lower six bits of the serial poll register. The mask thus enables bit 3, the Front Panel SRQ bit.

The SRQ mask codes can be added to select combinations of conditions.

Example Explanation

"* N5 P1 ?" An SRQ is generated if the SRQ button is pressed or if the trigger results

in an overrange reading. The SRQ mask is set to 05, which is 000101 in binary.

At power-up or on any device-clear command, the SRQ mask is set to 00 (decimal). This prevents service requests by holding the RQS bit false under all conditions. For other examples of the SRQ mask, see the description of the P1 command.

3-52. INTERFACE MESSAGES

The interface messages understood by the 8842A can be separated into the three main classes described in the IEEE-488 Standard: address me ssages (AD), un iversa l commands (UC), and addressed commands (AC). All interface messages described here originate at the controller.

3-53. Address Messages

Address messages are used by the controller to communicate talk and listen control to other devices on the bus. Address messages are sent over the eight data lines of the bus while the controller holds ATN true. Address messages are processed immediately and are not placed in the input buffer. The address messages are:

• MLA My Listen Address -- Addresses a device to listen

• MTA My Talk Address -- Addresses a device to talk

• UNL Unlisten -- Addresses all listeners to unlisten

• UNT Untalk -- Addresses all talkers to untalk

3-54. Universal Commands

Universal commands are accepted and interpreted by all devices on the bus. The commands are of two types, multiline messages and uniline messages. Multiline messages are sent over the eight parallel data lines in the IEEE-488 bus. Uniline messages are sent over one of the individual interface management lines in the IEEE-488 bus. All universal commands except DCL are processed immediately by the 8842A, ahead of any device-dependent commands. Only DCL enters the 8842A input buffer.

The 8842A responds to the following universal messages: ATN Attention -- A uniline message which causes the 8842A to interpret multiline

messages as interface messages (AD, AC, or UC). When false, multiline messages are interpreted as device-dependent messages.

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Instruction Manual

IFC Interface Clear -- A uniline message which clears only the interface (not the

8842A) by placing it in a known quiescent state.

REN Remote Enable -- A uniline message which, when received with MLA, switches

the 8842A to remote. When REN is set false, the 8842A switches to local and removes local lockout.

DCL Device Clea r -- A multi lin e mes sage wh ich is load ed into the input buff er as a

special device-clear command. DCL performs the same operation as the devicedependent command *, except that it is read before any other characters that are already present in the input buffer, and clears the entire input buffer. Processing then continues normally. The action of DCL is not immediate; if the 8842A is taking a reading when DCL is received, the DCL command is executed after the measurement is finished.

LLO Local Lockout -- A multiline message which disables the front panel LOCAL

button. The result is that the local mode is not accessible by front panel control.

SPD Serial Poll Disable -- A multiline message which removes the serial poll enable

state.

SPE Serial Poll Enable -- A multiline message which causes the serial poll data (rather

than output buffer data) to be transferred on the bus once ATN becomes false.

3-55. Addressed Commands

Addressed commands are multiline messages which are accepted and interpreted by only those devices currently addressed to listen. The 8842A responds to the following addressed commands:

GET Group Execute Trigger -- (Not to be confused with the device-dependent Get

commands.) GET loads a trigger command into the input buffer and also terminates the string at that point. Only a single character is loaded into the input buffer. The trigger command is executed in its proper turn in the input string, rather than immediately. When executed, GET initiates a measurement.

GTL Go To Local -- Causes the 8842A to switch to local. This command does not

enter the input buffer. If the display has been blanked (with a D1 command), issue a D0 command before sending GTL.

SDC Selected Device Clear -- Identical to the universal command DCL, but is

accepted and interpreted by current listeners only. Therefore, it clears the 8842A only if it is addressed to listen.

3-56. TALK-ONLY MODE

The talk-only mode lets you take advantage of the remote capability of the 8842A without having to use an instrument controller. To put the 8842A in the talk-only mode:

1. Turn the 8842A POWER switch OFF.

3-30

2. Set the rear panel TALK ONLY bit switch to 1 (the up position).

3. Connect the 8842A via the IEEE-488 bus to your printer, data logger, or other device.

4. Configure the other device as a listener only.

5. Turn the 8842A POWER switch ON.

6. Configure the 8842A with the front panel controls. The 8842A reads the TALK ONLY bit switch on power-up and when it receives the

interface command IFC. You can therefore set the TALK ONLY switch to 1 after powerup as long as you then send the 8842A the IFC command.

3-57. REMOTE CALIBRATION

The 8842A can be calibrated over the IEEE-488 bus using remote commands. Refer to the Maintenance section for details.

3-58. TIMING CONSIDERATIONS

To help you take the best advantage of the speed of the 8842A, external trigger timing for the IEEE-488 Interface is described in the specifications in Section 1.

3-59. IMMEDIATE MODE COMMANDS

Many controllers have some amount of "immediate mode" capability. That is, commands may be given interactively to the 8842A via the run-time-system without the need for actually running a program. The controller accepts and executes these commands one at a time. Some commonly used commands are listed in Table 3-3 for several controllers. These are provided for the convenience of instrument demonstrations, set-up and checkout, and for those with limited experience with IEEE-488 bus operations.

Remote Programming

REMOTE CALIBRATION

As a general note: The entire 8842A command set should work well provided the "port clear" and "device clear" commands are given first. You should then be able to send any other commands in the 8842A command set without repeating the clearing commands.

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Instruction Manual

Table 3-3. Immediate-Mode Commands for Various Controllers

FUNTION

PERFORMED

INITIALIZE Port INIT PORT 0 cli 7 CLEAR 7 INIT

CLEAR Instrument CLEAR @4 cir 704 CLEAR 704 PRINT @4: “*”

REMOTE Commands REMOTE @4 rem 704 REMOTE 704 WBYTE @36, 17: LOCAL Control LOCAL @4 Icl 704 LOCAL 704 WBYTE @36, 1: EXTERNAL TRIGGER PRINT @4,”T1” wrt 704,”T1” OUTPUT 704;”T1” PRINT @4:”T1” TRIGGER Instrument TRIG @4 trg 704 TRIGGER 704 PRINT @4:”?” GET Output Data INPUT @4,A red 704, A ENTER 704;A (Note 2) INPUT @4:A PRINT Data to Screen PRINT A prt A PRINT A (Note 2) PRINT A CONFIGURE for VAC PRINT @4,”F2” wrt 704,”F2” OUTPUT 704;”F2” PRINT @4:”F2” CONFIGURE for

200Vac TRIGGER Continuously PRINT @4,”TO” wrt 704,”TO” OUTPUT 704; “TO” PRINT @4:”TO” SUFFIXES Enable PRINT @4,”Y1” wrt 704,”Y1” OUTPUT 704;”Y1” PRINT @4:”Y1” GET Data & Suffix INPUT @4, A,A$ Red 704,A,A$

PRINT Data & Suffix PRINT A,A$ Prt A$,A PRINT A,A$ (Note 2) PRINT A,A$ Notes:

1. Before using A$ on the 9825 is necessary to enter ”dimA$[6]” to allocate a string variable. This statement allows six characters.

2. In the HP9816 system, variables cannot be created from the keyboard; they must be created by running a program. (See error 910 for that system.) To get around this, type in a very short program as follows:

SCRATCH (Hit “EXEC” key) 10 A = 0 (Hit “ENTER” key) 20 A$ = ‘’’’ (Hit “ENTER” key) 30 END (Hit “ENTER” key) (Hit “RUN” Key)

This program creates the variables ‘A’ and ‘A$’ so that they may be accessed in immediate mode and changed at will. This program is not necessary for the HP-85 Calculator.

FLUKE-BASIC on

1720A or 1722A

PRINT @4,”R4” wrt 704;”R4” OUTPUT 704;”R4” PRINT @4:”R4”

HP-HPL on

HP9825

Calculator

(Note 1)

HP-BASIC on

HP9816-PC and HP-

85 Calculator

ENTER 704;A,A$ (Note2)INPUT %4:A,A$

TEK-BASIC on

4051 Graphics

System

3-32

3-60. EXAMPLE PROGRAMS

Several example programs for the 8842A using various controllers are presented in the remaining figures in this section. In all of these examples, the 8842A is set to IEEE-488 address 4 (rear panel switch setting 000100). Of course, any other address (00 to 30) could be substituted.

In each of these examples, the instrument is cleared prior to configuration set-ups. This ensures that the 8842A configuration has been comple te ly def ined.

To run these programs, it is not necessary to type in all the comments (which appear to the right of the exclamation marks). Also, spaces are placed between commands for ease of reading; they are not required.

Remote Programming

EXAMPLE PROGRAMS

Figure 3-9. Example Program

f3-10.wmf

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Instruction Manual

3-34

Figure 3-10. Example Program: Taking Readings with Local Control

f3-11.wmf

Remote Programming

EXAMPLE PROGRAMS

Figure 3-11. Example Program: Using the Serial Poll Register

f3-12.wmf

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Instruction Manual

3-36

Figure 3-12. Example Program: Record Errors During Selftest

f3-13.wmf

Remote Programming

EXAMPLE PROGRAMS

Figure 3-13. Example Programs: Using the IBM PC

f3-14_01.wmf

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Instruction Manual

3-38

f3-14_01.wmf

Figure 3-14. Example Programs: Using the IBM PC (cont)

Remote Programming

EXAMPLE PROGRAMS

Figure 3-14. Example Programs: Using the IBM PC (cont)

f3-14_02.wmf

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8842A

Instruction Manual

3-40

f3-14_03.wmf

Figure 3-14. Example Programs: Using the IBM PC (cont)

Remote Programming

EXAMPLE PROGRAMS

Figure 3-14. Example Programs: Using the IBM PC (cont)

f3-14_04.wmf

3-41

8842A

Instruction Manual

3-42

f3-14_05.wmf

Figure 3-14. Example Programs: Using the IBM PC (cont)

Remote Programming

EXAMPLE PROGRAMS

Figure 3-14. Example Programs: Using the IBM PC (cont)

f3-14_06.wmf

3-43

8842A

Instruction Manual

3-44

f3-14_07.wmf

Figure 3-14. Example Programs: Using the IBM PC (cont)

Remote Programming

EXAMPLE PROGRAMS

Figure 3-14. Example Programs: Using the IBM PC (cont)

f3-14_08.wmf

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8842A

Instruction Manual

3-46

f3-14_09.wmf

Figure 3-14. Example Programs: Using the IBM PC (cont)

Remote Programming

EXAMPLE PROGRAMS

Figure 3-14. Example Programs: Using the IBM PC (cont)

f3-14_10.wmf

3-47

8842A

Instruction Manual

3-48

f3-14_11.wmf

Figure 3-14. Example Programs: Using the IBM PC (cont)

Table 3-4. ASCII/IEEE Std 488-1978 Bus Codes

Remote Programming

EXAMPLE PROGRAMS

3-49

8842A

Instruction Manual

NOTE

For the examples using the Fluke 1720A or 1722A, the 8842A is plugged into port 0. The port is initialized by the INIT statement, which sends IFC (interface clear).

3-50

Chapter 4

Measurement Tutorial

Title Page

4-1. INTRODUCTION................................................................................4-2

4-2. DC VOLTAGE MEASUREMENT .....................................................4-2

4-3. Circuit Loading Error.......................................................................4-2

4-4. Input Bias Current Error...................................................................4-3

4-5. RESISTANCE MEASUREMENT ......................................................4-4

4-6. 2-Wire Ohms....................................................................................4-4

4-7. Correcting for Test Lead Resistance in 2-Wire Ohms.....................4-5

4-8. 4-Wire Ohms....................................................................................4-5

4-9. Applications of the Ohms Functions................................................4-7

4-10. TESTING DIODES.....................................................................4-7

4-11. TESTING ELECTROLYTIC CAPACITORS............................4-7

4-12. A PRECISION CURRENT SOURCE.........................................4-8

4-13. DC CURRENT MEASUREMENT .....................................................4-8

4-14. REDUCING THERMAL VOLTAGES...............................................4-9

4-15. AC VOLTAGE AND CURRENT MEASUREMENT........................4-10

4-16. True RMS Measurement..................................................................4-10

4-17. Waveform Comparison....................................................................4-10

4-18. Crest Factor......................................................................................4-12

4-19. AC-Coupled AC Measurements ......................................................4-12

4-20. Combined AC and DC Measurements.............................................4-13

4-21. Bandwidth........................................................................................4-13

4-22. Zero-Input VAC Error......................................................................4-13

4-23. MAKING ACCURATE MEASUREMENTS ON THE 20 mV

AND 20Ω RANGES ............................................................................4-14

4-24. MAKING ACCURATE HIGH-RESISTANCE MEASUREMENTS .4-15

4-1

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Instruction Manual

4-1. INTRODUCTION

4-2. DC VOLTAGE MEASUREMENT

4-3. Circuit Loading Error

This section discusses considerations and techniques to help you use the 8842A effectively. Among other things, this section discusses sources of error which are an inherent part of the measurement process and which occur for all multimeters. By understanding why and when these errors occur, and by knowing how and when to correct for them, you can make accurate measurements with confidence.

This section also discusses the relative benefits of 2-wire and 4-wire ohms, describes special considerations for making ac measurements, and presents some unusual applications--for example, using the test current in the 2-wire ohms function as a troubleshooting tool in itself.

When measuring dc voltages in high-impedance circuits, there are two possible sources of error to consider: circuit loading and input bias current.

Whenever a voltmeter is connected to a circuit, the voltmeter’s internal resistance changes the voltage of the circuit under test. The resulting error is called circuit loading error. The error is negligible as long as the resistance of the circuit under test (the source impedance) is small compared to the input impedance of the meter. As the source impedance approaches the input impedance of the voltmeter, the error can be considerable. The percentage of error can be calculated using the formula in Figure 4-1.

4-2

Figure 4-1. Circuit Loading Error Calculation

f4-01.wmf

The input impedance of the 8842A is 10 MΩ in the 200V and 1000V dc ranges, and is greater than 10,000 MΩ in the 20 mV, 200 mV, 2V, and 20V ranges. Therefore, for the 8842A, circuit loading error is less than 0.01% as long as the source impedance is less than 1 MΩ in the 20 mV, 200 mV, 2V, and 20V ranges, and less than 1 kΩ in the 200V and 1000V ranges. The exceptionally high input impedance on the 20V dc range allows high-accuracy readings in CMOS and high-impedance analog circuitry.

Input protection circuitry can reduce the input impedance to as low as 100

Ω

when the input is overrange. This may also occur momentarily when the

k instrument autoranges to a higher range.

4-4. Input Bias Current Error

Input bias current error occurs because a voltmeter’s input bias current always changes the voltage of the circuit under test. However, the error is significant only when measuring voltages in circuits with very high source impedance. The error can be measured as shown in Figure 4-2.

NOTE

Measurement Tutorial

DC VOLTAGE MEASUREMENT

Figure 4-2. Measuring Input Bias Current Error

With the 8842A, it is easy to correct for this error using the OFFSET button:

1. Select the VDC function and the desired range.

2. Connect the 8842A INPUT terminals to a resistor which matches the source

impedance of the circuit to be tested.

f4-02.wmf

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Instruction Manual

3. Allow the displayed reading to settle.

4. Press the OFFSET button.

5. Remove the resistor.

6. Proceed with the desired measurement. Example: Measure a 1.5V source with 1 MΩ source impedance, correcting for input bias current.

1. Connect a 1 MΩ resistor between the INPUT HI and INPUT LO terminals.

2. Select the VDC function and the 2V range.

3. Allow the display to settle.

4. Press OFFSET. (This zeroes the input bias current error.)

5. Remove the 1 MΩ resistor.

6. Measure the voltage of the circuit under test. Note that this procedure does not correct for circuit loading error. Also note that if input

bias current error is not corrected for, it may be added to the circuit loading error.

4-5. RESISTANCE MEASUREMENT

The 8842A allows you to measure resistance in both 2-wire and 4-wire configurations. Each has its benefits.

4-6. 2-Wire Ohms

Two-Wire ohms measurements are simple to set up and yield good results for most measurement conditions. Measurements are made as shown in Figure 4-3. An internal current source (the "ohms current source ") pass es a known test curre nt (I tes t) th rough the resistance being tested (Runknown). The 8842A measures the voltage drop across Runknown, calculates Runknown using Ohm’s law (Runknown = Vtest/Itest), and displays the result.

4-4

Figure 4-3. Wire Ohms Measurement

f4-03.wmf

The test current and full-scale voltage for each resistance range are shown in Table 4-1. Since the HI INPUT test lead is positive with respect to the LO INPUT lead, these test leads are not interchangeable when a semiconductor device is being measured.

4-7. Correcting for Test Lead Resistance in 2-Wire Ohms

In 2-wire ohms, the resistance of the test leads can introduce error when measuring low resistances. Typical test leads may add as much as 0.5Q to 2-wire ohms readings.

With the 8842A, it is easy to correct for this error using the OFFSET button:

1. Select the 2-wire ohms function.

2. Touch the test leads together. The 8842A should indicate the resistance of the test

leads.

3. With the test leads still touching, press the OFFSET button.The 8842A should read 0Ω.

4-8. 4-Wire Ohms

Four-Wire ohms measurements provide the highest accuracy for low resistance measurements. The 4-wire configuration automatically corrects for both test lead resistance and contact resistance. Contact resistance (the resistance between the test probe tips and the circuit being tested) is unpredictable, and therefore cannot be reliably corrected with a fixed offset.

Measurement Tutorial

RESISTANCE MEASUREMENT

Four-Wire ohms measurements are especially important when using long test leads. In a typical automated test system, for example, the test leads could be connected through four or five switching relays, each with 2Ω of resistance!

NOTE

Instability of the test lead’s resistance can cause significant error on low

Ω

ohms ranges, particularly on the 20 wire ohms measurement is permitted in the 20

The 8842A makes 4-wire ohms measurements as shown in Figure 4-4. The HI and LO INPUT leads apply a known, internal current source to the unknown resistance, just as in 2-wire ohms. (See Table 4-1.) However, the voltage drop across the unknown resistance is measured with the SENSE leads rather than the INPUT leads. Since the current flow in the SENSE leads is negligible, the error caused by the voltage drop across the leads is also negligible.

and 200Ω ranges. Therefore, only 4-

Ω

range.

4-5

8842A

Instruction Manual

4-6

Figure 4-4. Wire Ohms Measurement

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Table 4-1. Ohms Test Current

RANGE TEST CURRENT FULL SCALE VOLTAGE

20Ω 1 mA 0.02V

200Ω 1 mA 0.2V

2 kΩ 1 mA 2.0V

20 kΩ 100 µA2.0V

200 kΩ 10 µA2.0V

2000 kΩ 5 µA 10.0V

20 MΩ 500 nA 10.0V

NOTE

Ω

In the 2 M unknown resistance is sensed between the HI SENSE and LO INPUT terminals. Accuracy is not affected as long as the resistance of the LO INPUT lead is less than 10

Ω

20 M

4-9. Applications of the Ohms Functions

The 2-wire and 4-wire ohms functions can be used for a variety of purposes in addition to measuring resistance, as the following applications show.

4-10. TESTING DIODES

The 2-wire ohms function can also be used to test diodes.

1. Select the 2-wire ohms function and the 2 kΩ range.

2. Measure the resistance of the diode. If the diode is good, when forward-biased it will measure about 0.6 kΩ to 0.7 kΩ fo r silicon (0.25 kΩ to 0.3 kΩ for germanium), and when reverse-biased it will cause the 8842A to indicate overrange. (The forwardbiased reading depends upon the range used.)

and 20 MΩ ranges of 4-wire ohms, the voltage across the

Ω

in the 2 MΩ range, and less than 100Ω in the

range.

Measurement Tutorial

RESISTANCE MEASUREMENT

The 2 kΩ range is used because its 1 mA test current provides a typical operating point, and its 2V full-scale voltage is sufficient to turn on most diodes (even two diodes in series).

4-11. TESTING ELECTROLYTIC CAPACITORS

The 2-wire ohms function can also give a rough test of an electrolytic capacitor’s leakage and dielectric absorption. This test works well for capacitors 0.5 µF and larger.

1. Select the 2-wire ohms function, the 2 kΩ range, and the medium reading rate.

2. Connect the test leads to the capacitor (with the INPUT HI lead to the + lead and the INPUT LO lead to the - lead). The 8842A attempts to charge it to the open-circuit voltage of the 2 kΩ range (about 6V).

3. Disconnect the + test lead.

4. To test for leakage, select the VDC function and the 20V range (leave the 8842A in the medium reading rate), and measure the voltage that was stored on the capacitor during step 2.

a. If the capacitor is good, the voltage across the capacitor will be about 6V, and

will be relatively stable.

b. If the capacitor is leaky, the voltage across the capacitor will be much less than

6V, and the voltage will be decreasing. The rate of change depends on how leaky the capacitor is.

c. With some electrolytic capacitors, the reading will increase. This usually

indicates the capacitor is defective.

5. To test the capacitor’s dielectric absorption, briefly short the capacitor’s leads together and then measure the voltage across the capacitor.

a. If the dielectric is good (i.e., has low dielectric absorption), the voltage across the

capacitor will be nearly zero volts.

b. If the dielectric is poor (i.e., has high dielectric absorption), the voltage across the

capacitor will be significantly above zero.

4-7

8842A

Instruction Manual

4-12. A PRECISION CURRENT SOURCE

The ohms current source (the internal current source used in the ohms functions) makes a useful troubleshooting tool in itself. It has excellent linearity and temperature stability. Its compliance voltage is typically 5V in the lower five ohms ranges, and 12V in the upper two ohms ranges. The inputs are protected against accidental applications of voltage up to 300V rms.

To use the ohms current source, connect the test leads to the HI and LO INPUTS, and select either the 2-wire or 4-wire ohms function. Press the range buttons to select any of the current levels shown in Table 4-1.

The ohms current source can be used to troubleshoot circuits by injecting current into selected nodes, forcing the circuits to be in a specific test state. For example, the ohms current source can be used to set or modify the bias of amplifier circuits. The current level can be changed simply by changing range.

The ohms current source can also be used to test mA or µA panel meters. The accuracy of the current source is more than enough to verify panel meters, whose accuracy is typically 1% to 5%. To test an analog panel meter, simply connect the current source across the meter movement (as though mea sur ing it s resi sta nce ). A 1 mA meter should show full scale when the ohms function is set on the 2 kΩ range. The same technique also works with digital panel meters.

4-13. DC CURRENT MEASUREMENT

To get the best accuracy using the mA DC function, it is important to understand the concept of burden voltage error.

When a meter is placed in series with a circuit to measure current, error can be caused by the small voltage drop across the meter (in this case, across the protective fuses and current shunt). This voltage drop is called the burden voltage, and it is highest for fullscale measurements. The full-scale burden voltage for the 8842A is typically less than 1V.

The burden voltage can present a significant error if the current source being measured is unregulated (i.e., not a true current source) and if the resistance of the fuse and shunt is a significant part of the source resistance. If burden voltage does present a significant error, the percentage of error can be calculated and corrected for using the formulas in Figure 4-

4-8

Measurement Tutorial

REDUCING THERMAL VOLTAGES

Figure 4-5. Burden Voltage Error Calculation

4-14. REDUCING THERMAL VOLTAGES

When making very low-level dc measurements, thermal voltages can present an additional source of error. Thermal voltages are the thermovoltaic potentials generated at the junction between dissimilar metals. Thermal voltages typically occur at binding posts and can be greater than 10 µV.

Thermal voltages can also cause problems in the low dc and ohms ranges, particularly in the 20 mV and 20Ω ranges. Some low-value resistors are constructed with dissimilar metals. Just handling such resistors can cause thermal voltages large enough to introduce measurement errors.

The effect of thermal voltages can be reduced by using the following techniques:

1. Use tight connections.

2. Use clean connections (especially free of grease and dirt).

3. Use similar metals for connections wherever possible (e.g., copper-to-copper, goldto-gold, etc.).

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4-9

Fluke 8842a User Manual

Specifications and Main Features

Frequently Asked Questions

User Manual

Instruction Manual

Table of Contents

List of Tables

List of Figures

Introduction and Specifications

SPECIFICATIONS

Operating Instructions

2-3. Installing the Power-Line Fuse

2-4. Connecting to Line Power

2-5. Adjusting the Handle

2-6. Rack Mounting Kits

2-8. Power-Up Features

2-9. Front and Rear Panel Features

MAKING MEASUREMENTS

EXTERNAL CLEANING

Remote Programming

INTRODUCTION

3-7. Bn (Offset Commands)

3-8. Cn (Calibration Commands)

3-9. Dn (Display Commands)

MEASUREMENT DATA

SERVICE REQUESTS

INTERFACE MESSAGES

REMOTE CALIBRATION

Measurement Tutorial

4-3. Circuit Loading Error

4-4. Input Bias Current Error

4-6. 2-Wire Ohms

4-7. Correcting for Test Lead Resistance in 2-Wire Ohms

4-8. 4-Wire Ohms

4-9. Applications of the Ohms Functions

REDUCING THERMAL VOLTAGES