Fluke NetDAQ 2640A User manual

PN 942615
March 1995
© 1995 Fluke Corporation, Inc. All rights reserved. Printed in U.S.A.
All product names are trademarks of their respective companies.
®
2640A/2645A
NetDAQ Data Acquisition Tools
Service Manual

LIMITED WARRANTY & LIMITATION OF LIABILITY
Each Fluke product is warranted to be free from defects in material and workmanship under
normal use and service. The warranty period is one year and begins on the date of shipment.
Parts, product repairs and services are warranted for 90 days. This warranty extends only to the
original buyer or end-user customer of a Fluke authorized reseller, and does not apply to fuses,
disposable batteries or to any product which, in Fluke’s opinion, has been misused, altered,
neglected or damaged by accident or abnormal conditions of operation or handling. Fluke
warrants that software will operate substantially in accordance with its functional specifications for
90 days and that it has been properly recorded on non-defective media. Fluke does not warrant
that software will be error free or operate without interruption.
Fluke authorized resellers shall extend this warranty on new and unused products to end-user
customers only but have no authority to extend a greater or different warranty on behalf of Fluke.
Warranty support is available if product is purchased through a Fluke authorized sales outlet or
Buyer has paid the applicable international price. Fluke reserves the right to invoice Buyer for
importation costs of repair/replacement parts when product purchased in one country is submitted
for repair in another country.
Fluke’s warranty obligation is limited, at Fluke’s option, to refund of the purchase price, free of
charge repair, or replacement of a defective product which is returned to a Fluke authorized
service center within the warranty period.
To obtain warranty service, contact your nearest Fluke authorized service center or send the
product, with a description of the difficulty, postage and insurance prepaid (FOB Destination), to
the nearest Fluke authorized service center. Fluke assumes no risk for damage in transit.
Following warranty repair, the product will be returned to Buyer, transportation prepaid (FOB
Destination). If Fluke determines that the failure was caused by misuse, alteration, accident or
abnormal condition of operation or handling, Fluke will provide an estimate of repair costs and
obtain authorization before commencing the work. Following repair, the product will be returned to
the Buyer transportation prepaid and the Buyer will be billed for the repair and return
transportation charges (FOB Shipping Point).
THIS WARRANTY IS BUYER’S SOLE AND EXCLUSIVE REMEDY AND IS IN LIEU OF ALL
OTHER WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY
IMPLIED WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
FLUKE SHALL NOT BE LIABLE FOR ANY SPECIAL, INDIRECT, INCIDENTAL OR
CONSEQUENTIAL DAMAGES OR LOSSES, INCLUDING LOSS OF DATA, WHETHER
ARISING FROM BREACH OF WARRANTY OR BASED ON CONTRACT, TORT, RELIANCE OR
ANY OTHER THEORY.
Since some countries or states do not allow limitation of the term of an implied warranty, or
exclusion or limitation of incidental or consequential damages, the limitations and exclusions of
this warranty may not apply to every buyer. If any provision of this Warranty is held invalid or
unenforceable by a court of competent jurisdiction, such holding will not affect the validity or
enforceability of any other provision.
Fluke Corporation Fluke Europe B.V.
P.O. Box 9090 P.O. Box 1186
Everett WA 5602 B.D. Eindhoven
98206-9090 The Netherlands
5/94

SAFETY TERMS IN THIS MANUAL
This instrument has been designed and tested in accordance with IEC publication
1010-1 (1992-1), Safety Requirements for Electrical Measuring, Control and Laboratory
Equipment, and ANSI/ISA-582.01-1994, and CAN/CSA-C22.2 No. 1010.1-92. This User
Manual contains information, warning, and cautions that must be followed to ensure
safe operation and to maintain the instrument in a safe condition. Use of this equipment
in a manner not specified herein may impair the protection provided by the equipment.
This instrument is designed for IEC 1010-1 Installation Category II use. It is not
designed for connection to circuits rated over 4800 VA.
WARNING statements identify conditions or practices that could result in personal injury
or loss of life.
CAUTION statements identify conditions or practices that could result in damage to
equipment.
SYMBOLS MARKED ON EQUIPMENT
WARNING Risk of electric shock. Refer to the manual.
GROUND Ground terminal to chassis (earth).
Attention Refer to the manual. This symbol indicates that information
about usage of a feature is contained in the manual. This symbol
appears on the rear panel ground post and by the fuse compartment.
AC POWER SOURCE
The instrument is intended to operate from an ac power source that will not apply more
than 264V ac rms between the supply conductors or between either supply conductor
and ground. A protective ground connection by way of the grounding conductor in the
power cord is required for safe operation.
USE THE PROPER FUSE
To avoid fire hazard, for fuse replacement use only the specified unit: 15/100 ampere,
250V, time delay.
GROUNDING THE INSTRUMENT
The instrument utilizes controlled overvoltage techniques that require the instrument to
be grounded whenever normal mode or common mode ac voltages or transient voltages
may occur. The enclosure must be grounded through the grounding conductor of the
power cord, or through the rear panel ground binding post.

USE THE PROPER POWER CORD
Use only the power cord and connector appropriate for the voltage and plug
configuration in your country.
Use only a power cord that is in good condition.
Refer power cord and connector changes to qualified service personnel.
DO NOT OPERATE IN EXPLOSIVE ATMOSPHERES
To avoid explosion, do not operate the instrument in an atmosphere of explosive gas.
DO NOT REMOVE COVER DURING OPERATION
To avoid personal injury or death, do not remove the instrument cover without first
removing the power source connected to the rear panel. Do not operate the instrument
without the cover properly installed. Normal calibration is accomplished with the cover
closed. Access procedures and the warnings for such procedures are contained in this
manual. Service procedures are for qualified service personnel only.
DO NOT ATTEMPT TO OPERATE IF PROTECTION MAY BE IMPAIRED
If the instrument appears damaged or operates abnormally, protection may be impaired.
Do not attempt to operate the instrument under these conditions. Refer all questions of
proper instrument operation to qualified service personnel.

i
Table of Contents
Chapter Title Page
1 Introduction and Specification............................................................ 1-1
1-1. Introduction............................................................................................ 1-3
1-2. Options and Accessories ........................................................................ 1-6
1-3. Instrument Connector Set, 2620A-100 .............................................. 1-6
1-4. Host Computer Ethernet Interfaces.................................................... 1-6
1-5. Interconnection Cables and Components........................................... 1-6
1-6. Operating Instructions............................................................................ 1-7
1-7. Organization of the Service Manual....................................................... 1-7
1-8. Conventions............................................................................................ 1-8
1-9. Specifications......................................................................................... 1-8
1-10. 2640A/2645A Combined Specifications ........................................... 1-8
1-11. 2640A/2645A General Specifications........................................... 1-9
1-12. 2640A/2645A Environmental Specifications................................ 1-10
1-13. 2640A/2645A Input/Output Capabilities....................................... 1-10
1-18. 2640A/2645A Totalizer................................................................. 1-12
1-19. 2640A/2645A Real-Time Clock and Calendar.............................. 1-12
1-20. 2640A Specifications......................................................................... 1-13
1-21. 2640A DC Voltage Measurement Specifications.......................... 1-13
1-22. 2640A AC Voltage Measurement Specifications.......................... 1-14
1-23. 2640A Four-Wire Resistance Measurement Specifications.......... 1-16
1-24. 2640A Two-Wire Resistance Measurement Specifications.......... 1-16
1-25. 2640A Four-Wire RTD per ITS-1990 Measurement
Specifications.............................................. .................................. 1-17
1-26. 2640A Two-Wire RTD per ITS-1990 Measurement
Specifications.............................................. .................................. 1-17
1-27. 2640A Thermocouple per ITS-1990 Measurement
Specifications.............................................. .................................. 1-18
1-28. 2640A Frequency Measurement Specifications............................ 1-19
1-29. 2645A Specifications......................................................................... 1-20
1-30. 2645A DC Voltage Measurement Specifications.......................... 1-20
1-31. 2645A AC Voltage Measurement Specifications.......................... 1-21
1-32. 2645A Four-Wire Resistance Measurement Specifications.......... 1-23
1-33. 2645A Two-Wire Resistance Measurement Specifications.......... 1-23

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1-34. 2645A Four-Wire RTD per ITS-1990 Measurement
Specifications................................................................................. 1-24
1-35. 2645A Thermocouple per ITS-1990 Measurement
Specifications................................................................................. 1-24
1-36. 2645A Frequency Measurement Specifications............................ 1-26
2 Theory of Operation............................................................................. 2-1
2-1. Introduction............................................................................................ 2-5
2-2. Functional Block Description................................................................. 2-5
2-3. A1 Main PCA Block Description ...................................................... 2-7
2-4. Power Supply................................................................................. 2-7
2-5. Digital Kernel ................................................................................ 2-7
2-6. Serial Communication (Guard Crossing) ...................................... 2-8
2-7. Digital Inputs and Outputs............................................................. 2-8
2-8. Ethernet Interface .......................................................................... 2-8
2-9. A2 Display PCA Block Description .................................................. 2-8
2-10. A3 A/D Converter PCA Block Description....................................... 2-8
2-11. Analog Measurement Processor.................................................... 2-9
2-12. Input Protection ............................................................................. 2-9
2-13. Input Signal Conditioning.............................................................. 2-9
2-14. Analog-to-Digital (a/d) Converter................................................. 2-9
2-15. Inguard Microcontroller ................................................................ 2-9
2-16. Channel Selection.......................................................................... 2-9
2-17. Open Thermocouple Check........................................................... 2-10
2-18. A4 Analog Input PCA Block Description.......................................... 2-10
2-19. 20-Channel Terminals ................................................................... 2-10
2-20. Reference Junction Temperature................................................... 2-10
2-21. Detailed Circuit Description .................................................................. 2-10
2-22. A1 Main PCA Circuit Description..................................................... 2-10
2-23. Power Supply Circuit Description................................................. 2-10
2-31. Digital Kernel ................................................................................ 2-13
2-42. Digital Inputs and Outputs............................................................. 2-24
2-48. A2 Display PCA Circuit Description................................................. 2-26
2-49. Main PCA Connector .................................................................... 2-26
2-50. Front Panel Switches..................................................................... 2-27
2-51. Display........................................................................................... 2-28
2-52. Beeper Drive Circuit...................................................................... 2-28
2-53. Watchdog Timer and Reset Circuit............................................... 2-29
2-54. Display Controller ......................................................................... 2-29
2-55. A3 A/D Converter PCA Circuit Description..................................... 2-31
2-56. Stallion Chip.................................................................................. 2-33
2-57. Input Protection ............................................................................. 2-33
2-58. Input Signal Conditioning.............................................................. 2-33
2-59. Function Relays............................................................................. 2-33
2-60. Channel Selection Circuitry........................................................... 2-34
2-61. DC Volts and Thermocouples Measurement Circuitry................. 2-34
2-62. Ohms and RTD Measurement Circuitry........................................ 2-36
2-63. AC Volts Measurement Circuitry.................................................. 2-37
2-64. Frequency Measurements.............................................................. 2-37
2-65. Active Filter (ACV Filter)............................................................. 2-37
2-66. Voltage Reference Circuit............................................................. 2-38
2-67. Analog/Digital Converter Circuit.................................................. 2-39
2-73. Inguard Digital Kernel Circuitry ................................................... 2-42
2-74. Open Thermocouple Detect Circuitry............................................. 2-43

Contents (continued)
iii
2-75. A4 Analog Input PCA Circuit Description........................................ 2-43
2-76. A1 Main to A3 A/D Converter Communications................................... 2-44
2-77. Special Codes..................................................................................... 2-44
2-78. Resets................................................................................................. 2-44
2-79. Commands.......................................................................................... 2-45
2-80. Perform Scan ................................................................................. 2-45
2-81. Perform Self-Test........................................................................... 2-46
2-82. Return Main Firmware Version..................................................... 2-46
2-83. Return Boot Firmware Version ..................................................... 2-47
2-84. Set Global Configuration............................................................... 2-47
2-85. Set Channel Configuration ............................................................ 2-47
2-86. Do Housekeeping........................................................................... 2-48
2-87. Checksums ......................................................................................... 2-48
2-88. Errors.................................................................................................. 2-48
2-89. Power-Up Protocol............................................................................. 2-49
2-90. Inguard Unresponsive ........................................................................ 2-49
2-91. Inguard Software Description ................................................................ 2-49
2-92. Hardware Elements............................................................................ 2-49
2-93. Channel MUX.... ........................................................................... 2-49
2-94. Function Relays. ........................................................................... 2-51
2-95. Stallion Chip and Signal Conditioning.......................................... 2-51
2-96. A/D ................................................................................................ 2-53
2-101. DISCHARGE Signal. .................................................................... 2-57
2-102. Open-Thermocouple Detector. ...................................................... 2-57
2-103. Channel Measurements...................................................................... 2-57
2-104. Reading Rates................................................................................ 2-57
2-105. Measurement Types....................................................................... 2-58
2-112. Autoranging................................................................................... 2-60
2-113. Overload ........................................................................................ 2-61
2-114. Housekeeping Readings..................................................................... 2-61
2-115. Reading Types ............................................................................... 2-61
2-118. Housekeeping Schedule................................................................. 2-62
2-119. Self-Tests ........................................................................................... 2-62
2-120. Power-Up Self-Tests...................................................................... 2-62
2-121. Self-Test Command....................................................................... 2-63
3 General Maintenance........................................................................... 3-1
3-1. Introduction............................................................................................ 3-3
3-2. Warranty Repairs and Shipping ............................................................. 3-3
3-3. General Maintenance.............................................................................. 3-3
3-4. Required Equipment .......................................................................... 3-3
3-5. Power Requirements .......................................................................... 3-3
3-6. Static-Safe Handling.......................................................................... 3-3
3-7. Servicing Surface-Mount Assemblies................................................ 3-4
3-8. Cleaning.................................................................................................. 3-4
3-9. Replacing the Line Fuse......................................................................... 3-5
3-10. Disassembly Procedures......................................................................... 3-7
3-11. Removing the Instrument Case.......................................................... 3-7
3-12. Removing the Front Panel Assembly................................................. 3-7
3-13. Disassembling the Front Panel Assembly.......................................... 3-11
3-14. Removing the A1 Main PCA............................................................. 3-11
3-15. Removing the A2 Display PCA......................................................... 3-12
3-16. Removing the A3 A/D Converter PCA.............................................. 3-12
3-17. Removing the A4 Analog Input PCA ................................................ 3-12

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3-18. Removing Miscellaneous Chassis Components ................................ 3-12
3-19. Removing the Power Switch/Input Connector .............................. 3-12
3-20. Removing the Fuseholder.............................................................. 3-13
3-21. Removing the Power Transformer................................................. 3-13
3-22. Assembly Procedures ............................................................................. 3-13
3-23. Installing Miscellaneous Chassis Components.................................. 3-13
3-24. Installing the Power Transformer.................................................. 3-13
3-25. Installing the Fuseholder ............................................................... 3-14
3-26. Installing the Power Switch/Input Connector................................ 3-14
3-27. Installing the A1 Main PCA............................................................... 3-15
3-28. Installing the A2 Display PCA........................................................... 3-15
3-29. Installing the A3 A/D Converter PCA............................................... 3-15
3-30. Installing the A4 Analog Input PCA.................................................. 3-15
3-31. Assembling the Front Panel Assembly.............................................. 3-16
3-32. Installing the Front Panel Assembly.................................................. 3-16
3-33. Installing the Instrument Case............................................................ 3-16
4 Performance Testing and Calibration................................................. 4-1
4-1. Introduction............................................................................................ 4-3
4-2. Performance Test ................................................................................... 4-3
4-3. Configuring the Performance Test Setup........................................... 4-3
4-4. Initializing the Performance Test Setup............................................. 4-6
4-5. Accuracy Performance Tests ............................................................. 4-7
4-6. Volts DC Accuracy Test (2640A)................................................. 4-8
4-7. Volts DC Accuracy Test (2645A)................................................. 4-9
4-8. Volts AC Accuracy Test................................................................ 4-10
4-9. Frequency Accuracy Test.............................................................. 4-10
4-10. Analog Channel Integrity Test....................................................... 4-11
4-11. Computed Channel Integrity Test.................................................. 4-11
4-12. Thermocouple Temperature Accuracy Test.................................. 4-12
4-13. Open Thermocouple Response Test.............................................. 4-12
4-14. Two-Terminal Resistance Accuracy Test (2640A)....................... 4-13
4-15. Two-Terminal Resistance Accuracy Test (2645A)....................... 4-14
4-16. Four-Terminal Resistance Accuracy Test (2640A)....................... 4-15
4-17. Four-Terminal Resistance Accuracy Test (2645A)....................... 4-17
4-18. RTD Temperature Accuracy Test (Resistance) (2640A).............. 4-18
4-19. RTD Temperature Accuracy Test (Resistance) (2645A).............. 4-19
4-20. RTD Temperature Accuracy Test (DIN/IEC 751 RTD) ............... 4-19
4-21. Digital Input/Output Tests ................................................................. 4-20
4-22. Digital I/O Output Test.................................................................. 4-20
4-23. Digital Input Test........................................................................... 4-21
4-24. Totalizer Tests........................................................................................ 4-22
4-25. Totalizer Count Test...................................................................... 4-22
4-26. Totalizer Sensitivity Test............................................................... 4-23
4-27. Master Alarm Output Test................................................................. 4-23
4-28. Trigger Input Test .............................................................................. 4-24
4-29. Trigger Output Test............................................................................ 4-24
4-30. Calibration.............................................................................................. 4-25
4-31. Methods of Calibration...................................................................... 4-25
4-32. Preparing for Calibration ................................................................... 4-26
4-33. Ending Calibration............................................................................. 4-28
4-34. RS-232 Instrument Configuration Parameters................................... 4-28
4-35. Calibration Procedure (Automatic).................................................... 4-28
4-36. Calibration Procedure (Semiautomatic)............................................. 4-28

Contents (continued)
v
4-37. VDC Calibration Procedure........................................................... 4-31
4-38. VAC Calibration Procedure........................................................... 4-32
4-39. Resistance Calibration Procedure.................................................. 4-33
4-40. Frequency Calibration Procedure.................................................. 4-34
4-41. Calibration Procedure (Manual) ........................................................ 4-34
4-42. Manual Calibration Commands..................................................... 4-36
4-43. Manual VDC Calibration Procedure ............................................. 4-37
4-44. Manual VAC Calibration Procedure ............................................. 4-38
4-45. Manual Resistance Calibration Procedure..................................... 4-39
4-46. Manual Frequency Calibration Procedure..................................... 4-41
5 Diagnostic Testing and Troubleshooting........................................... 5-1
5-1. Introduction............................................................................................ 5-3
5-2. Servicing Surface-Mount Assemblies.................................................... 5-3
5-3. Error Detection....................................................................................... 5-4
5-4. FLASH ROM Parameter Defaults..................................................... 5-5
5-5. Background Testing........................................................................... 5-5
5-6. Internal Software Errors..................................................................... 5-6
5-7. Retrieving Error Codes using RS-232................................................ 5-6
5-8. Retrieving Error Codes using the Network........................................ 5-6
5-9. Selecting the Diagnostic Tools............................................................... 5-6
5-10. Diagnostic Tool dio............................................................................ 5-7
5-11. Diagnostic Tool idS ........................................................................... 5-7
5-12. Diagnostic Tool conF......................................................................... 5-8
5-13. Diagnostic Display Test..................................................................... 5-9
5-14. COMM Parameter Reset.................................................................... 5-9
5-15. Using the RS-232 Interface.................................................................... 5-9
5-16. Command Processing......................................................................... 5-10
5-17. Instrument Configuration................................................................... 5-11
5-18. Command Set ......................................................................................... 5-12
5-19. Troubleshooting the Instrument ............................................................. 5-19
5-20. General Troubleshooting ................................................................... 5-19
5-21. A1 Main PCA Troubleshooting......................................................... 5-27
5-22. Troubleshooting the A1 Main PCA Digital Kernel....................... 5-27
5-23. Troubleshooting the RS-232 Interface........................................... 5-28
5-24. Troubleshooting the Ethernet Interface......................................... 5-28
5-25. Troubleshooting the Digital I/O Lines and Trigger Out Lines...... 5-28
5-26. Troubleshooting the Totalizer and Trigger In Lines ..................... 5-28
5-27. Troubleshooting the Power Supply ............................................... 5-29
5-28. A2 Display PCA Troubleshooting..................................................... 5-29
5-29. Variations in the Display............................................................... 5-31
5-30. A3 A/D Converter PCA Troubleshooting.......................................... 5-31
5-31 A3 Kernel. ..................................................................................... 5-32
5-32. Break/Reset Circuit........................................................................ 5-32
5-33. Out of Tolerance Readings............................................................ 5-32
5-34. Troubleshooting Relay Problems .................................................. 5-33
5-35. A4 Analog Input PCA Troubleshooting ............................................ 5-33
5-36. Troubleshooting Calibration Failures .................................................... 5-34
5-37. Retrieving Calibration Constants....................................................... 5-34
5-38. Loading Embedded Instrument Firmware.............................................. 5-36
5-39. Firmware Diskette.............................................................................. 5-36
5-40. Loading the Main Firmware .............................................................. 5-37
5-41. Loading the A/D Firmware................................................................ 5-38

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6 List of Replaceable Parts .................................................................... 6-1
6-1. Introduction............................................................................................ 6-3
6-2. How To Obtain Parts.............................................................................. 6-3
6-3. Manual Status Information..................................................................... 6-3
6-4. Newer Instruments.................................................................................. 6-4
6-5. Service Centers....................................................................................... 6-4
7 Schematic Diagrams............................................................................ 7-1

vii
List of Tables
Table Title Page
1-1. Summary of 2640A/2645A Specifications............................................. 1-4
1-2. Summary of 2640A/2645A Measurement Capabilities ......................... 1-4
1-3. Summary of 2640A/2645A Features...................................................... 1-5
1-4. Models, Options and Accessories.......................................................... 1-6
1-5. 2640A/2645A General Specifications.................................................... 1-9
1-6. Environmental Specifications ................................................................ 1-10
1-7. 2640A/2645A DIGITAL I/O Specification............................................ 1-10
1-8. 2640A/2645A Trigger In (TI) Specification.......................................... 1-11
1-9. 2640A/2645A Trigger Out (TO) Specification...................................... 1-11
1-10. 2640A/2645A Master Alarm (MA) Specification ................................. 1-11
1-11. 2640A/2645A Totalizer Specification ................................................... 1-12
1-12. 2640A/2645A Real-Time Clock and Calendar ...................................... 1-12
1-13. 2640A DC Voltage General Specifications ........................................... 1-13
1-14. 2640A DC Voltage Range and Resolution Specifications..................... 1-13
1-15. 2640A DC Voltage Accuracy Specifications......................................... 1-14
1-16. 2640A AC Voltage General Specifications ........................................... 1-14
1-17. 2640A AC Voltage Range and Resolution Specifications..................... 1-15
1-18. 2640A AC Voltage Accuracy Specifications......................................... 1-15
1-19. 2640A Four-Wire Resistance Temperature Coefficient......................... 1-16
1-20. 640A Four-Wire Resistance Range and Resolution Specifications....... 1-16
1-21. 2640A Four-Wire Resistance Accuracy Specifications......................... 1-16
1-22. 2640A Four-Wire RTD Temperature Coefficient.................................. 1-17
1-23. 2640A Four-Wire RTD Specifications .................................................. 1-17
1-24. 2640A Thermocouple General Specifications ....................................... 1-18
1-25. 2640A Thermocouple Specifications..................................................... 1-18
1-26. 2640A Frequency Accuracy Specifications........................................... 1-19
1-27. 2640A Frequency Sensitivity Specifications ......................................... 1-20
1-28. 2645A DC Voltage General Specifications ........................................... 1-20
1-29. 2645A DC Voltage Resolution and Repeatability Specifications.......... 1-21
1-30. 2645A DC Voltage Accuracy Specifications......................................... 1-21
1-31. 2645A AC Voltage General Specifications ........................................... 1-21
1-32. 2645A AC Voltage Range and Resolution Specifications..................... 1-22
1-33. 2645A AC Voltage Accuracy Specifications......................................... 1-22
1-34. 2645A Four-Wire Resistance Temperature Coefficient......................... 1-23
1-35. 2645A Four-Wire Resistance Range and Resolution Specifications..... 1-23

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1-36. 2645A Four-Wire Resistance Accuracy Specifications......................... 1-23
1-37. 2645A Four-Wire RTD Temperature Coefficient.................................. 1-24
1-38. 2645A Four-Wire RTD Specifications .................................................. 1-24
1-39. 2645A Thermocouple General Specifications ....................................... 1-24
1-40. 2645A Thermocouple Specifications..................................................... 1-25
1-41. 2645A Frequency Accuracy Specifications........................................... 1-26
1-42. 2645A Frequency Sensitivity Specifications ......................................... 1-26
2-1. Microprocessor Interrupt Sources.......................................................... 2-16
2-2. Booting Microprocessor Memory Map.................................................. 2-17
2-3. nstrument Microprocessor Memory Map............................................... 2-17
2-4. A2 Display Power Supply Connections................................................. 2-27
2-5. Front Panel Switch Scanning ................................................................. 2-28
2-6. Display Initialization Modes.................................................................. 2-30
2-7. Range of Buffer Amplifier..................................................................... 2-34
2-8. Measurement Matrix for DC Volts ........................................................ 2-35
2-9. Measurement Matrix for Ohms.............................................................. 2-36
2-10. Measurement Matrix for AC Volts ........................................................ 2-37
2-11. Analog/Digital Converter Measurement Cycle...................................... 2-39
2-12. Tree Bits................................................................................................. 2-50
2-13. Channel Bits........................................................................................... 2-50
2-14. Tree and Channel Switch Settling Times............................................... 2-50
2-15. Function Relays...................................................................................... 2-51
2-16. Function Relay Settling Time................................................................. 2-51
2-17. Stallion Switch Settings ......................................................................... 2-52
2-18. Signal Conditioning Settling Time......................................................... 2-53
2-19. A/D Command Codes............................................................................. 2-55
2-20. A/D Readings to Average to Obtain a Measurement............................. 2-58
2-21. Frequency Sensitivity............................................................................. 2-60
2-22. A/D Readings to Average to Obtain a Reference
Balance Measurement ............................................................................ 2-61
4-1. Recommended Test Equipment.............................................................. 4-4
4-2. RS-232 Instrument Configuration for Calibration Procedures............... 4-28
4-3. Calibration Commands........................................................................... 4-36
4-4. Manual Calibration Command Responses............................................. 4-37
4-5. Manual VDC Calibration....................................................................... 4-37
4-6. Manual VAC Calibration....................................................................... 4-39
4-7. Manual Resistance Calibration .............................................................. 4-40
4-8. Manual Frequency Calibration............................................................... 4-41
5-1. Selftest Error Codes ............................................................................... 5-4
5-2. FLASH ROM Parameter Defaults ......................................................... 5-5
5-3. Corrective Action for Background Error Checking............................... 5-6
5-4. Instrument Firmware Descriptions......................................................... 5-8
5-5. Instrument Default COMM Parameters ................................................. 5-9
5-6. Instrument Configuration ....................................................................... 5-11
5-7. RS232 Command Set ............................................................................. 5-12
5-8. Power-on/Reset Instrument State........................................................... 5-14
5-9. Range Settings........................................................................................ 5-18
5-10. Selftest Error Codes ............................................................................... 5-20
5-10. Relating Selftest Errors to Instrument Problems.................................... 5-21
5-10. Relating Selftest Errors to Instrument Problems.................................... 5-22
5-10. Relating Selftest Errors to Instrument Problems.................................... 5-23
5-10. Relating Selftest Errors to Instrument Problems.................................... 5-24
5-10. Relating Selftest Errors to Instrument Problems.................................... 5-25
5-11. Hints for Troubleshooting...................................................................... 5-26
5-12. A1 Main PCA Jumper Positions ............................................................ 5-27

Tables (continued)
ix
5-13. A2 Display PCA Initialization Routines ................................................ 5-29
5-14. A3 A/D Converter PCA Jumper Positions............................................. 5-32
5-15. Calibration Constants............................................................................. 5-35
5-16. Files on the Firmware Diskette .............................................................. 5-37
6-1. 2640A/2645A Final Assembly............................................................... 6-5
6-2. A1 Main PCA Assembly........................................................................ 6-10
6-3. A2 Display PCA Assembly.................................................................... 6-15
6-4. 2640A A3 A/D Converter PCA Assembly............................................. 6-17
6-5. 2645A A3 A/D Converter PCA Assembly............................................. 6-22
6-6. A4 Analog Input PCA Assembly ........................................................... 6-27

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xi
List of Figures
Figure Title Page
1-1. 2640A/2645A NetDAQ Networked Data Acquisition Units................. 1-3
2-1. Interconnection Diagram........................................................................ 2-5
2-2. Overall Functional Block Diagram ........................................................ 2-6
2-3. Power Supply Block Diagram................................................................ 2-7
2-4. Command Byte Transfer Waveforms..................................................... 2-29
2-5. Grid Control Signal Timing ................................................................... 2-30
2-6. Grid-Anode Timing Relationships......................................................... 2-31
2-7. A3 A/D Converter Block Diagram......................................................... 2-32
2-8. DC Volts 300V Range Simplified Schematic........................................ 2-35
2-9. RTD Measurement Simplified Schematic.............................................. 2-36
2-10. AC Volts 3V Range Simplified Schematic............................................ 2-38
2-11. Integrator Output Waveform for Input Near 0....................................... 2-40
2-12. Integrator Output Waveform for Input Near + Full Scale...................... 2-41
2-13. Integrator Output Waveform for Input Near - Full Scale....................... 2-41
2-14. A/D Timing (2645A Normal Reading) .................................................. 2-54
2-15. A/D Timing (2640A Normal Reading, 2640A and
2645A Reference Balance)..................................................................... 2-54
2-16. A/D Status Signals.................................................................................. 2-55
3-1. Replacing the Fuse ................................................................................. 3-6
3-2. 2640A and 2645A Assembly Details..................................................... 3-8
3-3. Power Input Connections at the Power Switch...................................... 3-14
4-1. Performance Test Setup ......................................................................... 4-5
4-2. Two-Terminal Connections to 5700A.................................................... 4-5
4-3. Four-Terminal Connections to the Universal Input Module (Resistor). 4-15
4-4. Four-Terminal Connections to the Universal Input Module (5700A) ... 4-16
4-5. Instrument and Host Computer Calibration Setup................................. 4-27
4-6. Universal Input Module Calibration Connections ................................. 4-27
4-7. Two-Wire Calibration Connection......................................................... 4-29
4-8. Four-Wire Calibration Connection......................................................... 4-29
5-1. Display Test Pattern #1.......................................................................... 5-29
5-2. Display Test Pattern #2.......................................................................... 5-30
5-3. Connection to A3P1 for Loading A/D Firmware................................... 5-39
6-1. 2640A/264A5 Final Assembly............................................................... 6-9
6-1. 701/702 Final Assembly......................................................................... 6-9
6-2. A1 Main PCA Assembly........................................................................ 6-14

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6-2. A1 Power Supply PCA........................................................................... 6-14
6-3. A2 Display PCA Assembly.................................................................... 6-16
6-4. 2640A A3 A/D Converter PCA Assembly............................................. 6-21
6-5. 2645A A3 A/D Converter PCA Assembly............................................. 6-26
6-6. A4 Analog Input PCA Assembly ........................................................... 6-28

1-1
Chapter 1
Introduction and Specification
Title Page
1-1. Introduction............................................................................................ 1-3
1-2. Options and Accessories ........................................................................ 1-6
1-3. Instrument Connector Set, 2620A-100.............................................. 1-6
1-4. Host Computer Ethernet Interfaces................................................... 1-6
1-5. Interconnection Cables and Components.......................................... 1-6
1-6. Operating Instructions............................................................................ 1-7
1-7 Organization of the Service Manual ...................................................... 1-7
1-8. Conventions............................................................................................ 1-8
1-9. Specifications......................................................................................... 1-8
1-10. 2640A/2645A Combined Specifications........................................... 1-8
1-11. 2640A/2645A General Specifications.......................................... 1-9
1-12. 2640A/2645A Environmental Specifications............................... 1-10
1-13. 2640A/2645A Input/Output Capabilities ..................................... 1-10
1-14. Digital I/O.................................................................................1-10
1-15. Trigger In..................................................................................1-11
1-16. Trigger Out ...............................................................................1-11
1-17. Master Alarm............................................................................1-11
1-18. 2640A/2645A Totalizer................................................................ 1-12
1-19. 2640A/2645A Real-Time Clock and Calendar ............................ 1-12
1-20. 2640A Specifications ........................................................................ 1-13
1-21. 2640A DC Voltage Measurement Specifications ........................ 1-13
1-22. 2640A AC Voltage Measurement Specifications ........................ 1-14
1-23. 2640A Four-Wire Resistance Measurement Specifications......... 1-16
1-24. 2640A Two-Wire Resistance Measurement Specifications......... 1-16
1-25. 2640A Four-Wire RTD per ITS-1990 Measurement
Specifications ............................................................................... 1-17
1-26. 2640A Two-Wire RTD per ITS-1990 Measurement
Specifications ............................................................................... 1-17
1-27. 2640A Thermocouple per ITS-1990 Measurement
Specifications. .............................................................................. 1-18
1-28. 2640A Frequency Measurement Specifications........................... 1-19

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1-29. 2645A Specifications ........................................................................ 1-20
1-30. 2645A DC Voltage Measurement Specifications ........................ 1-20
1-31. 2645A AC Voltage Measurement Specifications ........................ 1-21
1-32. 2645A Four-Wire Resistance Measurement Specifications......... 1-23
1-33. 2645A Two-Wire Resistance Measurement Specifications......... 1-23
1-34. 2645A Four-Wire RTD per ITS-1990 Measurement
Specifications ............................................................................... 1-24
1-35. 2645A Thermocouple per ITS-1990 Measurement
Specifications. .............................................................................. 1-24
1-36. 2645A Frequency Measurement Specifications........................... 1-26

Introduction and Specification
Introduction
1
1-3
Introduction 1-1.
This Service Manual supports performance testing, calibration, servicing, and
maintenance of the 2640A NetDAQ™and 2645A NetDAQ networked data acquisition
units (Figure 1-1). NetDAQ networked data acquisition units are 20-channel front ends
that operate in conjunction with a host computer to form a networked data acquisition
system. The host computer and instruments are interconnected using an Ethernet
network, and the host computer runs the NetDAQ Logger for Windows application to
provide an operating environment for the instruments, including testing and calibration.
The 2640A and 2645A networked data acquisition units are identical in operation and
appearance, and vary only in emphasis: The 2640A emphasizes precision and supports
up to 100 measurements per second, with 5 ½ digits of resolution, .02% accuracy, and
150-volt common mode voltage (300 volts on channels 1 and 11), while the 2645A
emphasizes increased measurement speed supporting up to 1000 measurements per
second, with 4 ½ digits of resolution, .04% accuracy, and 50-volt common mode voltage.
Refer to Table 1-1 for a summary of instrument specifications. For complete instrument
specifications, see “Specifications” later in this chapter.
The instruments measure dc volts, ac volts, ohms, temperature, frequency, and dc
current. Temperature measurements use thermocouples or resistance-temperature
detectors (RTDs). Refer to Table 1-2 for a summary of instrument measurement
capabilities. In addition, there are eight digital input/output lines, one totalizing input,
one external trigger input, one trigger output, and one master alarm output. The
instruments can be ac or dc powered. An RS-232 serial port is supplied for servicing and
maintenance procedures.
The term "instrument" is used in this manual to refer to both units. The model number
(2640A or 2645A) is used when discussing characteristics unique to one instrument.
Instrument assemblies are identical except for the A3 Analog/Digital Converter printed
circuit assembly (pca), which is specific to the 2640A (mechanical switching for
measurement signals) and 2645A (solid-state switching for measurement signals).
The instrument is designed for bench-top, field service, and system applications. A dual
vacuum-fluorescent display uses combinations of alphanumeric characters and
descriptive annunciators to provide prompting and measurement information during
setup and operation modes. Some features provided by the instrument are listed in Table
1-3. For additional information regarding instrument features and capabilities, refer to
the NetDAQ Users Manual (PN 942623).
NetDAQ
NETWORKED DATA ACQUISITION UNIT
COMM DIO MON
ENTER
CAL
ENABLE
REM SCAN
MON
V DC
CH
Figure 1-1. 2640A/2645A NetDAQ Networked Data Acquisition Units

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Table 1-1. Summary of 2640A/2645A Specifications
Specification 2640A 2645A
Maximum Normal Mode Voltage 150/300V [1] 50V
Maximum Common Mode
Voltage 150/300V [1] 50V
Input (Overload) Protection 1600V 300V
Maximum Reading Rates
(Volts DC Only) 143 readings/second (scanning 20 channels) 1000 readings/second (scanning 20 channels)
Maximum Single Channel Scan
Reading Rates [2] 80 readings/second (Drift Correction enabled) 250 readings/second (Drift Correction enabled)
120 readings/second
(Drift Correction disabled) 400 readings/second (Drift Correction disabled)
Volts DC Accuracy (90 day),
1V dc input 0.02% 0.04%
Thermocouple Accuracy
(90 day) 0.3°C0.6°C
Resistance-Temperature
Detectors (RTDs) Resolution 0.003°C 0.03°C
Resistance-Temperature
Detectors (RTDs) Accuracy 0.12°C0.2°C
Time to Change Functions
(Between V dc, V ac,
Frequency, and Ohms)
6 ms 6 ms
[1] The 300V value is for channels 1 and 11 only; the 150V value is for all other channels.
[2] Drift Correction refers to an automatic internal measurement step performed with each
scan to correct for drift due to changes in ambient temperature and humidity.
Table 1-2. Summary of 2640A/2645A Measurement Capabilities
Capability 2640A 2645A
Volts DC Measurements Ranges: 90 mV
300 mV
3V
30V
150/300V [1]
Autorange
Ranges: 90 mV
300 mV
3V
30V
50V
Autorange
Volts AC Measurements Ranges: 300 mV
3V
30V
150/300V [1]
Autorange
Ranges: 300 mV
3V
30V
Autorange
Resistance Measurements Ranges: 300 Ω
3 kΩ
30 kΩ
300 kΩ
3 MΩ
Autorange
Ranges: 30 kΩ
300 kΩ
3 MΩ
Autorange