® 8842A Digital Multimeter Instruction Manual PN 879309 Date December 1991 Rev.3 7/96 © 1999 Fluke Corporation, All rights reserved. Printed in USA All product names are trademarks of their respective companies.
Table of Contents Chapter 1 Title Introduction and Specifications........................................................ 1-1 1-1. 1-2. 1-3. 1-4. 2 Page INTRODUCTION................................................................................ THE 8842A DIGITAL MULTIMETER .............................................. OPTIONS AND ACCESSORIES ........................................................ SPECIFICATIONS ..............................................................................
8842A Instruction Manual 2-28. 2-29. 2-30. 3 Current Fuse Protection.................................................................... 2-13 Offset Measurements ....................................................................... 2-14 EXTERNAL CLEANING.................................................................... 2-15 Remote Programming........................................................................ 3-1 3-1. 3-2. 3-3. 3-4. 3-5. 3-6. 3-7. 3-8. 3-9. 3-10. 3-11. 3-12. 3-13. 3-14. 3-15.
Contents (continued) 3-50. 3-51. 3-52. 3-53. 3-54. 3-55. 3-56. 3-57. 3-58. 3-59. 3-60. 4 3-27 3-28 3-29 3-29 3-29 3-30 3-30 3-31 3-31 3-31 3-32 Measurement Tutorial........................................................................ 4-1 4-1. 4-2. 4-3. 4-4. 4-5. 4-6. 4-7. 4-8. 4-9. 4-10. 4-11. 4-12. 4-13. 4-14. 4-15. 4-16. 4-17. 4-18. 4-19. 4-20. 4-21. 4-22. 4-23. 4-24. 5 The Serial Poll Register ................................................................... The SRQ Mask........................
8842A Instruction Manual 5-15. 5-16. 5-17. 5-18. 5-19. 5-20. 5-21. 5-22. 5-23. 5-24. 5-25. 5-26. 5-27. 5-28. 5-29. 5-30. 5-31. 5-32. 5-33. 5-34. 5-35. 5-36. 5-37. 5-38. 5-39. 5-40. 5-41. 5-42. 5-43. 5-44. 5-45. 5-46. 5-47. 6 OHMS CURRENT SOURCE .............................................................. OHMS PROTECTION......................................................................... OHMS FUNCTIONS ........................................................................... 2-Wire Ohms...........
Contents (continued) 6-20. 6-21. 6-22. 6-23. 6-24. 6-25. 6-26. 6-27. 6-28. 6-29. 6-30. 6-31. 6-32. 6-33. 6-34. 6-35. 6-36. 6-37. 6-38. 6-39. 6-40. 6-41. 6-48. 6-59. 6-62. 6-63. 6-64. 6-65. 6-66. 6-67. 6-68. 6-69. 6-70. 6-71. 6-72. 6-73. 6-74. 6-75. 6-76. 6-77. 6-78. 7 List of Replaceable Parts................................................................... 7-1 7-1. 7-2. 7-3. 7-4. 7-5. 8 TOLERANCE CHECK ...............................................................
842A Instruction Manual 8-5. 8-6. 8-7. 8-8. 8-9. 8-10. 8-11. 8-12. 805 INTRODUCTION................................................................................ CAPABILITIES ................................................................................... EXTERNAL CONTROLS................................................................... INSTALLATION ................................................................................. PROGRAMMING INSTRUCTIONS............................................
List of Tables Table 2-1. 2-2. 3-1. 3-2. 3-8. 3-3. 3-4. 4-1. 5-1. 6-1. 6-2. 6-3. 6-4. 6-5. 6-6. 6-7. 6-8. 6-9. 6-10. 6-11. 6-12. 6-13. 6-14. 6-15. 6-16. 6-17. 6-18. 6-19. 6-20. 6-21. 6-22. 6-23. 6-24. 6-25. 6-26. Title Error Codes ............................................................................................................ Input Overload Limits............................................................................................ Status Data ............................................
8842A Instruction Manual 6-27. AC Signal Tracing ................................................................................................. 6-28. Truth Table for U804 and K2 ................................................................................ 7-1. 8842A Digital Multimeter...................................................................................... 7-2. A1 Main PCA ........................................................................................................ 7-3.
List of Figures Figure 1-1. 2-1. 2-2. 2-3. 2-4. 2-5. 2-6. 2-7. 2-8. 2-9. 2-10. 3-1. 3-2. 3-3. 3-4. 3-5. 3-6. 3-6. 3-7. 3-9. 3-10. 3-11. 3-12. 3-13. 4-1. 4-2. 4-3. 4-4. 4-5. 4-6. 4-7. 4-8. 4-9. 4-10. 4-11. Title External Dimensions.............................................................................................. Line Voltage Selection Settings............................................................................. Adjusting the Handle .......................................................
8842A Instruction Manual 4-12. Leakage Resistance in High Resistance Measurement .......................................... 5-1. Overall Functional Block Diagram........................................................................ 5-2. DC Scaling (VDC and mA DC)............................................................................. 5-3. Track/Hold Amplifier ............................................................................................ 5-4. Track/Hold Circuit Configurations ..........
Contents (continued) 9-7. 9-8. IEEE-488 Interface PCA, Option -05 .................................................................... 9-15 True RMS AC PCA, Option -09............................................................................
8842A Instruction Manual xii
Chapter 1 Introduction and Specifications Title 1-1. 1-2. 1-3. 1-4. Page INTRODUCTION................................................................................1-2 THE 8842A DIGITAL MULTIMETER ..............................................1-2 OPTIONS AND ACCESSORIES ........................................................1-2 SPECIFICATIONS ..............................................................................
8842A Instruction Manual 1-1. INTRODUCTION 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.
Introduction and Specifications SPECIFICATIONS 1 1-4. SPECIFICATIONS Specifications for the 8842A are given in Table 1-1. External dimensions are shown in Figure 1-1. Table 1-1. Specifications DC VOLTAGE Input Characteristics RANGE FULL SCALE 5ñ DIGITS RESOLUTION 5ñ DIGITS 4ñ DIGITS* INPUT RESISTANCE 20 mV 19.9999 mV 0.1µV 1 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 µV 1 mV ≥10,000 MΩ 200V 199.
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 FILTER NMRRï PEAK NM SIGNAL CMRRð S 2.
Introduction and Specifications SPECIFICATIONS 1 Accuracy NORMAL (s) READING RATE .............. ±(% of Reading + Number of Counts). For sinewave inputs ≥10,000 counts . 1 2 FREQUENCY 24 HOURS 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 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.
8842A Instruction Manual CURRENT Input Characteristics RANGE FULL SCALE 5½ DIGITS RESOLUTION 5½ DIGITS 4½ DIGITS 2 199.999 mA 1 µA 10 µA 2000 mA 1999.99 mA 10 µA 100 µA 200 mA 1. 4½ digits at the fastest reading rate. 2. The 200mA range is available for dc current only. 1 DC Accuracy 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 ≤1A 0.04 + 4 0.05 + 4 0.
Introduction and Specifications SPECIFICATIONS 1 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 ...........................
8842A Instruction Manual Accuracy 1 NORMAL (S) READING RATE ...............±(% of Reading + Number of Counts) . RANGE 24 HOURS 23±1°C 90 DAY 23±5°C 4 0.009 + 40 0.0040 + 3 5 0.007 + 4 2 kΩ 0.0025 + 2 20 kΩ 20Ω 3 5 1 YEAR 23±5°C 4 0.012 + 40 2 YEARS 23±1°C 4 0.015 + 40 5 0.012 + 4 0.005 + 3 0.008 + 3 0.010 + 3 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.
Introduction and Specifications SPECIFICATIONS 1 Reading Rates READING RATES WITH INTERNAL TRIGGER (readings per second) RATE POWER LINE FREQUECNCY 50 Hz 1 60 Hz 2 400 Hz 2 S 2.08 (.26) 2.5 (.31) M 16.7 (1.04) 20 (1.25) F 100 100 2 2.38 (.30) 2 2 19.0 (1.19) 2 100 1. Sensed automatically at power-up. 2. In 20 mV, 20 ohm, and 200 mA DC ranges.
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.
Introduction and Specifications SPECIFICATIONS 1 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 ..................................................
Chapter 2 Operating Instructions Title 2-1. 2-2. 2-3. 2-4. 2-5. 2-6. 2-7. 2-8. 2-9. 2-10. 2-11. 2-12. 2-13. 2-14. 2-15. 2-16. 2-17. 2-18. 2-19. 2-20. 2-21. 2-22. 2-23. 2-24. 2-25. 2-26. 2-27. 2-28. 2-29. 2-30. Page INTRODUCTION................................................................................2-2 INSTALLATION .................................................................................2-2 Installing the Power-Line Fuse ........................................................
8842A Instruction Manual 2-1. INTRODUCTION This section provides instructions for installing and operating the 8842A. Refer to Section 4 for measurement considerations. 2-2. INSTALLATION 2-3. Installing the Power-Line Fuse 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.
Operating Instructions INSTALLATION 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.
8842A Instruction Manual f2-04.wmf 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.
Operating Instructions OPERATING FEATURES 2 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: DC Volts HIGH and LO SENSE Terminals for 4-Wire Ohms Only 4-Wire Ohms AC Volts* DC Current 2-Wire Ohms AC Current* CAL ENABLE switch enables calibration mode. (CAUTION! See text.
8842A Instruction Manual TRIG triggers a new reading. Enabled in external trigger mode. 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.
Operating Instructions OPERATING FEATURES SAMPLE COMPLETE output TTL-level.
8842A Instruction Manual 2-10. Display Features The 8842A features a vacuum fluorescent display with a numeric field and annunciators. The annunciators are explained in Figure 2-5. 2-11. Error Messages 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.
Operating Instructions OPERATING FEATURES 2 Table 2-1.
8842A Instruction Manual 2-12. Overrange Indication 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.
Operating Instructions OPERATING FEATURES 2 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.
8842A Instruction Manual 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. 2-21.
Operating Instructions MAKING MEASUREMENTS 2 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.
8842A Instruction Manual 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. 2-29.
Operating Instructions EXTERNAL CLEANING 2 f2-09.wmf Figure 2-9. Measuring Voltage and Resistance f2-10.wmf 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. Should the 8842A case require cleaning, wipe the instrument with a cloth that is lightly dampened with water or a mild detergent solution.
8842A Instruction Manual 2-16
Chapter 3 Remote Programming Title 3-1. 3-2. 3-3. 3-4. 3-5. 3-6. 3-7. 3-8. 3-9. 3-10. 3-11. 3-12. 3-13. 3-14. 3-15. 3-16. 3-17. 3-18. 3-19. 3-20. 3-21. 3-22. 3-23. 3-24. 3-25. 3-26. 3-27. 3-28. 3-29. 3-30. 3-31. 3-32. 3-33. 3-34. Page INTRODUCTION................................................................................3-3 CAPABILITIES ...................................................................................3-3 BUS SET-UP PROCEDURE ........................................................
8842A Instruction Manual 3-35. 3-36. 3-37. 3-38. 3-39. 3-40. 3-41. 3-42. 3-43. 3-44. 3-45. 3-46. 3-47. 3-48. 3-49. 3-50. 3-51. 3-52. 3-53. 3-54. 3-55. 3-56. 3-57. 3-58. 3-59. 3-60. 3-2 ? (Single-Trigger Command) ...........................................................3-20 INPUT SYNTAX .................................................................................3-20 Definitions........................................................................................3-21 Input Processing..............
Remote Programming INTRODUCTION 3 NOTE 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.
8842A Instruction Manual A D D R E S S T A L K 00 0 0 0 0 0 01 0 0 0 0 02 0 0 0 03 0 0 04 0 05 A5 A4 A3 A2 A1 A D D R E S S T A L K A5 A4 A3 A2 A1 A D D R E S S T A L K 0 11 0 0 1 0 1 1 22 0 1 0 1 1 0 0 1 12 0 0 1 1 0 0 23 0 1 0 1 1 1 0 1 0 13 0 0 1 1 0 1 24 0 1 1 0 0 0 0 0 1 1 14 0 0 1 1 1 0 25 0 1 1 0 0 1 0 0 1 0 0 15 0 0 1 1 1 1 26 0 1 1 0 1 0 0 0 0 1 0 1 16 0 1 0 0 0 0 27 0 1
Remote Programming AN OVERVIEW OF REMOTE OPERATION 3 f3-02.wmf Figure 3-2.
8842A Instruction Manual 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. 3-5.
Remote Programming DEVICE-DEPENDENT COMMAND SET 3 TRIGGER COMMANDS ? Trigger Measurement GET Trigger and Execute TRIGGER MODE COMMANDS T0 T1-T4 Continuous Trigger External Trigger DISPLAY COMMANDS READING RATE COMMANDS SUFFIX COMMANDS D0 Normal Display D1 Blank Display Y0 Disable Suffix Y1 Enable Suffix S0 Slow S1 Medium S2 Fast M RANGE COMMANDS Sensed by G5 FUNCTION COMMANDS F1 F2 F3 F4 F5 F6 VDC VAC 2 Wire kΩ 4 Wire kΩ mA DC mA AC SELF-TEST COMMANDS R0 R1 R2 R3 R4 R5 Autorange On 200 mV, 20
8842A Instruction Manual FUNCTON COMMANDS TERMINATOR COMMANDS F1 VDC (Default) W0 Enable CR LF EOI (Default) F2 VAC W1 Enable CR LF Only F3 2 WIRE kΩ W2 Enable CR EOI Only F4 4 WIRE kΩ W3 Enable CR Only F5 MA DC W4 Enable LF EOI Only F6 MA 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 default conditions) R3 20V, 20 kΩ X0 Clear Error Register R5 1000V dc, 700V ac, 2 MΩ, 20
Remote Programming DEVICE-DEPENDENT COMMAND SET 3 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.
8842A Instruction Manual 3-10. Fn (Function 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).
Remote Programming DEVICE-DEPENDENT COMMAND SET 3 Table 3-1. Status Data COMMAND G0 OUTPUT STRING Frst MEANING F= r= s= t= G1 G3 G4 nn aaaaaaaaaaaaaaaa 10vm nn = 00 for SRQ disabled (default) 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.
8842A Instruction Manual 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.
Remote Programming DEVICE-DEPENDENT COMMAND SET 3 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.
8842A Instruction Manual 3-17. G5 (Get IAB 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.
Remote Programming DEVICE-DEPENDENT COMMAND SET 3 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.
8842A Instruction Manual "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.
Remote Programming DEVICE-DEPENDENT COMMAND SET 3 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 Where is a string of up to 16 ASCII characters. Example Explanation "P3FL.8842.
8842A Instruction Manual 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. f3-07.
Remote Programming DEVICE-DEPENDENT COMMAND SET 3 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.
8842A Instruction Manual 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.
Remote Programming INPUT SYNTAX 3 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.
8842A Instruction Manual 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 digit (n). Numeric-entry Characters NE.
Remote Programming INPUT SYNTAX 3 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.
8842A Instruction Manual In this incorrect example, the INPUT statement is located incorrectly 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 100 200 300 PRINT @3, "T1 ?" INPUT @3, A PRINT @3, "F4" In this example, the reading taken at line 100 is read at line 200. Then the F4 command is sent.
Remote Programming OUTPUT DATA 3 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.
8842A Instruction Manual NOTE In the fast (F) reading rate, the least significant digit is always zero, and should be disregarded when interpreting accuracy specifications. 3-45. OVERRANGE INDICATION If a reading is overrange (≥ 200,000 counts), the measurement data has the following format: ±9.99999E+9 Overvoltage readings (> 1000V dc or 700V ac) do not result in this display. 3-46.
Remote Programming SERVICE REQUESTS 3 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.
8842A Instruction Manual BIT: 8 7 6 5 4 0 RQS ANY ERROR DATA AVAILIBLE DECIMAL VALUE: 64 32 16 Bit Name 3 CAL STEP FRONT COMPLETE PANEL SRQ 8 4 Set 2 1 0 OVERRANGE 2 1 Cleared 1 Overrange An overrange condition occurs Device command received, or Bus or Rear Panel Trigger, or Output buffer is read 2 Not used Never Always 3 Front panel SRQ Front panel SRQ button pressed Device command received 4 Cal Step Complete Completion of store command (C0) Device command receive
Remote Programming INTERFACE MESSAGES 3 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.
8842A 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 Clear -- A multiline message which is loaded into the input buffer as a special device-clear command.
Remote Programming REMOTE CALIBRATION 3 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.
8842A Instruction Manual Table 3-3.
Remote Programming EXAMPLE PROGRAMS 3 f3-10.wmf Figure 3-9.
8842A Instruction Manual f3-11.wmf Figure 3-10.
Remote Programming EXAMPLE PROGRAMS 3 f3-12.wmf Figure 3-11.
8842A Instruction Manual f3-13.wmf Figure 3-12.
Remote Programming EXAMPLE PROGRAMS 3 f3-14_01.wmf Figure 3-13.
8842A Instruction Manual f3-14_01.wmf Figure 3-14.
Remote Programming EXAMPLE PROGRAMS 3 f3-14_02.wmf Figure 3-14.
8842A Instruction Manual f3-14_03.wmf Figure 3-14.
Remote Programming EXAMPLE PROGRAMS 3 f3-14_04.wmf Figure 3-14.
8842A Instruction Manual f3-14_05.wmf Figure 3-14.
Remote Programming EXAMPLE PROGRAMS 3 f3-14_06.wmf Figure 3-14.
8842A Instruction Manual f3-14_07.wmf Figure 3-14.
Remote Programming EXAMPLE PROGRAMS 3 f3-14_08.wmf Figure 3-14.
8842A Instruction Manual f3-14_09.wmf Figure 3-14.
Remote Programming EXAMPLE PROGRAMS 3 f3-14_10.wmf Figure 3-14.
8842A Instruction Manual f3-14_11.wmf Figure 3-14.
Remote Programming EXAMPLE PROGRAMS 3 Table 3-4.
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).
Chapter 4 Measurement Tutorial Title 4-1. 4-2. 4-3. 4-4. 4-5. 4-6. 4-7. 4-8. 4-9. 4-10. 4-11. 4-12. 4-13. 4-14. 4-15. 4-16. 4-17. 4-18. 4-19. 4-20. 4-21. 4-22. 4-23. 4-24. Page INTRODUCTION................................................................................4-2 DC VOLTAGE MEASUREMENT .....................................................4-2 Circuit Loading Error.......................................................................4-2 Input Bias Current Error...................................
8842A Instruction Manual 4-1. INTRODUCTION 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.
Measurement Tutorial DC VOLTAGE MEASUREMENT 4 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.
8842A 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.
Measurement Tutorial RESISTANCE MEASUREMENT 4 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.
8842A Instruction Manual f4-04.wmf Figure 4-4. Wire Ohms Measurement Table 4-1. Ohms Test Current 4-6 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 µA 2.0V 200 kΩ 10 µA 2.0V 2000 kΩ 5 µA 10.0V 20 MΩ 500 nA 10.
Measurement Tutorial RESISTANCE MEASUREMENT 4 NOTE In the 2 MΩ and 20 MΩ ranges of 4-wire ohms, the voltage across the 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 10Ω in the 2 MΩ range, and less than 100Ω in the 20 MΩ range. 4-9.
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.
Measurement Tutorial REDUCING THERMAL VOLTAGES 4 f4-05.wmf 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.
8842A Instruction Manual 4. Use caution when handling the circuit under test. 5. Wait for the circuit to reach thermal equilibrium. (Thermal voltages are generated only where there is a temperature gradient.) 4-15. AC VOLTAGE AND CURRENT MEASUREMENT When making precise measurements of ac voltage and current, there are several considerations in addition to those discussed under dc voltage and current measurement. These include the concepts of rms conversion, crest factor, bandwidth, and zero-input error.
Measurement Tutorial AC VOLTAGE AND CURRENT MEASUREMENT 4 f4-06.wmf Figure 4-6. Waveform Comparison Chart Since average-responding meters have been in use for so long, you may have accumulated test or reference data based on them. The conversion factors in Figure 4-6 should help you convert between the two measurement methods.
8842A Instruction Manual 4-18. Crest Factor Crest factors are useful for expressing the ability of an instrument to measure a variety of waveforms accurately. The crest factor of a waveform is the ratio of its peak voltage to its rms voltage. (For waveforms where the positive and negative half-cycles have different peak voltages, the more extreme peak is used in computing the crest factor.) Crest factors start at 1.
Measurement Tutorial AC VOLTAGE AND CURRENT MEASUREMENT 4 measurements, for instance, cannot be made with dc coupling. Remember, however, that when the 8842A measures signals with the ac functions, the reading on the display does not include the dc component (if one exists). For example, consider Figure 4-8, which shows a simple ac signal riding on a dc level. The VAC function would measure the ac component only. f4-08.wmf Figure 4-8. Combined AC and DC Measurement 4-20.
8842A Instruction Manual The zero-input error is quickly reduced when the input is increased. The rms converter error (a dc error) and the internally generated noise (a random ac error) are both uncorrelated with the input signal. Therefore, when a signal is applied, the resulting reading is not the simple addition of the signal and the zero-input error, but the square root of the sum of their squares. This reduces the effect of the error, as shown in the example in Figure 4-9. f4-09.wmf Figure 4-9.
Measurement Tutorial MAKING ACCURATE HIGH-RESISTANCE MEASUREMENTS 4 f4-10.wmf Figure 4-10. Shielding for Low Voltage Measurements For low-level resistance measurements, connect the test lead shielding as shown in Figure 4-11. Use the 4-wire ohms function to minimize the error caused by the resistance of the test leads. f4-11.wmf Figure 4-11. Shielding for Low Resistance Measurements Errors due to thermal voltages should also be considered when making low-level voltage or resistance measurements.
8842A Instruction Manual f4-12.wmf Figure 4-12.
Chapter 5 Theory of Operation Title 5-1. 5-2. 5-3. 5-4. 5-5. 5-6. 5-7. 5-8. 5-9. 5-10. 5-11. 5-12. 5-13. 5-14. 5-15. 5-16. 5-17. 5-18. 5-19. 5-20. 5-21. 5-22. 5-23. 5-24. 5-25. 5-26. 5-27. 5-28. 5-29. 5-30. 5-31. 5-32. 5-33. 5-34. 5-35. INTRODUCTION................................................................................ OVERALL FUNCTIONAL DESCRIPTION ...................................... DETAILED CIRCUIT DESCRIPTION .............................................. DC SCALING ......................
8842A Instruction Manual 5-36. 5-37. 5-38. 5-39. 5-40. 5-41. 5-42. 5-43. 5-44. 5-45. 5-46. 5-47. 5-2 POWER SUPPLY ................................................................................ IEEE-488 INTERFACE (OPTION -05)............................................... Out-Guard Microcomputer............................................................... Guard Crossing................................................................................. Bus Interface Circuitry.............................
Theory of Operation INTRODUCTION 5 5-1. INTRODUCTION This section presents an overall functional description of the 8842A, followed by a detailed circuit description. The descriptions are supported by simplified schematics in text and by the complete schematics in Section 10. 5-2. OVERALL FUNCTIONAL DESCRIPTION A functional block diagram of the 8842A is shown in Figure 5-1. The basic signal path flows from left to right across the center of the page.
8842A Instruction Manual 5-3. DETAILED CIRCUIT DESCRIPTION The following paragraphs give a detailed circuit description of each of the functional blocks in Figure 5-1. For clarity, measurement ranges are referred to as r1, r2, r3, etc., where r1 is the lowest possible range, r2 the next higher range, and so on. Pins are designated by the respective integrated circuit (e.g., U101-7 for U101 pin 7). 5-4.
Theory of Operation DC SCALING 5 f5-01.wmf Figure 5-1.
8842A Instruction Manual 5-5. VDC Scaling Scaling is performed in the VDC function by two precision resistors networks (Z301 and Z302). These components are configured by relay K301, switching transistor Q311, and quad analog switches U302A and U301B to provide the correct scaling for each range. Voltage follower U306 provides high input impedance for the 20V dc range. A simplified schematic and a switch state table for the VDC function are shown in Figure 5-2. f5-02.wmf Figure 5-2.
Theory of Operation DC SCALING 5 In the 20 mV, 200 mV and and 2V ranges, the input voltage is applied directly to the T/H Amplifier via Q310, Q311, and U301B. In the 20 mV range, the T/H Amplifier has a gain of 100; in the 200 mV range, the T/H Amplifier has a gain of 10; in all other dc voltage ranges, the T/H Amplifier has a gain of 1. In the 20V range, the input voltage is buffered by unity-gain amplifier U306, and divided by 10 by Z301.
8842A Instruction Manual 5-9. TRACK/HOLD CIRCUIT The Track/Hold (T/H) circuit presents a stable voltage to the A/D Converter during the input period of the A/D conversion cycle. The circuit also provides a gain of 100 in the 20 mV, 20Ω and 200 mA ranges, and a gain of 10 in the 200 mV dc, 200Ω, and 2000 mA dc ranges. The T/H circuit consists of the T/H Amplifier (Figure 5-3), T/H capacitor C308, quad analog switches U301, U302, and U303, and associated components.
Theory of Operation TRACK/HOLD CIRCUIT 5 f5-04.wmf Figure 5-4.
8842A Instruction Manual f5-05.wmf Figure 5-5. Timing Diagram for One A/D Cycle 5-10. Track Configuration In the track configuration (Figure 5-4A), the T/H circuit functions as a non-inverting buffer. The voltage on C308 tracks the scaled dc input voltage.
Theory of Operation PRECISION VOLTAGE REFERENCE 5 5-11. Settling Configuration The circuit assumes a settling configuration between the track and hold configurations. The circuit assumes the configuration in Figure 5-4B for unity gain and the configuration in Figure 5-4C for gain of 10. During this time the DC Scaling circuit is still connected to the T/H amp. However, changes in the input do not affect the value to be measured, which is stored on C308. 5-12.
8842A Instruction Manual Resistor R701, precision resistor network Z701, and transistor/zener diode combination U701 are produced as a matched set so that the output of U702A is precisely -7.00000V. This output is remotely sensed at the pins of the custom A/D IC (U101). Diode CR701 prevents the output from going positive at power-up. U702B functions as an inverter to provide the +7.00000V output and to supply the reference amplifier.
Theory of Operation OHMS PROTECTION 5 The second stage (U404, precision resistor network Z401, and analog switches U402 and U403) is a current amplifier whose gain is controlled by the In-Guard µC. The In-Guard µC sets the output current for each range by controlling U402 and U403. (See switch state table in Figure 5-7.) 5-16.
8842A Instruction Manual f5-08.wmf Figure 5-8.
Theory of Operation A/D CONVERTER 5 The voltage sensed at the INPUT terminals is scaled as shown by the simplified switch table in Figure 5-8. (Refer to the track period of the track/hold cycle, during which the scaled input voltage is sampled.) In the lower five ranges, the full scale input voltage to the A/D Converter is 2V. However, in the 2000 kΩ and 20 MΩ ranges, the full-scale input voltage to the A/D Converter is +1V; the in-guard uC completes the scaling by multiplying the A/D result by 2. 5-19.
8842A Instruction Manual f5-09.wmf Figure 5-9. Analog-to-Digital Converter The conversion process is broken up into an autozero period followed by five measurement intervals. (A timing diagram is shown in Figure 5-5.) Six bits of the final A/D sample are obtained during each interval. During the first compare period (shown in Figure 5-9), the A/D Converter determines the value of the scaled input voltage (Vin) by comparing Vin to the output of the DAC.
Theory of Operation A/D CONVERTER 5 f5-10.wmf Figure 5-10. First Remainder-Store Period This five-interval process thus generates five nibbles which are processed by the InGuard µC to produce one A/D sample. After the fifth nibble is generated, U101 interrupts the In-Guard µC over line INT. The In-Guard µC then pulls line CS7 low five times, causing U101 to send the µC the five (six-bit) nibbles one-at-a-time over lines AD0AD5.
8842A Instruction Manual The bit-switches determine the output voltage of U102B by controlling the binary ladder network. The gain of U102B is set by the ratio of a precision feedback resistor (Z101-7, 8) and the equivalent output resistance of the ladder network. 5-23. A/D Amplifier The A/D Amplifier is composed of a comparator/amplifier (U103), two remainderstorage capacitors (C103 and C102), an autozero storage capacitor (C101), and several digitally controlled analog switches contained in U101.
Theory of Operation KEYBOARD 5 f5-12.wmf Figure 5-12. Vacuum Fluorescent Display The Digital Controller sequentially enables the G lines by applying +30V dc (nominal). When a G line is enabled, electrons flow from the filament to the enabled grid. If a P line is enabled (i.e., raised to a nominal +30V dc by the Digital Controller), the electrons continue past the grid and strike the respective plate, causing it to glow. 5-26.
8842A Instruction Manual f5-13.wmf Figure 5-13.
Theory of Operation DIGITAL CONTROLLER 5 5-28. In-Guard Microcomputer The In-Guard Microcomputer (µC) is a single-chip Z8 microcomputer containing 4K bytes of ROM, 144 bytes of RAM, a UART, and four 8-bit I/O ports. It communicates with the rest of the instrument via the internal bus and dedicated I/O lines. The In-Guard µC is reset when pin 6 is pulled low either by C204 at power-up or by the watch-dog timer in the custom A/D IC (U101). Pin 6 is tied to +5V through a 100 kΩ resistor inside the µC.
8842A Instruction Manual f5-14.wmf Figure 5-14.
Theory of Operation DIGITAL CONTROLLER 5 5-29. Function and Range Control The In-Guard µC configures the DC Scaling circuit, the Track/Hold circuit, and the Ohms Current Source to provide the proper input switching, scaling, and filtering for each function, range, and reading rate. It does this by controlling dedicated output lines which control relays and FET switches, and by sending configuration codes out on the bus.
8842A Instruction Manual 5-32. Keyboard/Display Control Keyboard/Display Controller U212 communicates with the In-Guard µC over the internal bus. During a µC write cycle, address line A0 tells U212 whether to consider data being sent by the µC as configuration commands or as display data. Display data is stored in the Keyboard/Display Controller, which automatically scans the display. The Keyboard/Display Controller selects one of eight grids using decoder U213 and buffer U215.
Theory of Operation POWER SUPPLY 5 The circuit in Figure 5-15 has two stable states, corresponding to output high (+5V) and output low (0V). If the output is high, the voltage present at the non-inverting input of op amp A is approximately +140 mV. Since the inputs to op amps A and B are inverted, their outputs are always in opposite states.
8842A Instruction Manual 5-37. IEEE-488 INTERFACE (OPTION -05) The IEEE-488 Interface has five major parts, as shown in the block diagram in Figure 516. All components are contained in a single printed circuit assembly (PCA). Reference designations are numbered in the 900 series. f5-16.wmf Figure 5-16. IEEE-488 Interface Block Diagram 5-38. Out-Guard Microcomputer The Out-Guard Microcomputer (µC) (U901) communicates with the IEEE-488 talker/listener IC (U911) and the In-Guard µC (U202).
Theory of Operation TRUE RMS AC (OPTION -09) 5 5-41. Signal Conditioning The SAMPLE COMPLETE and EXT TRIG signals (J903 and J904) are conditioned by U909. Diodes CR903, CR904, CR905, and CR906 and resistors R917 and R918 provide protection from excessive voltages. Jumpers E902 and E903 allow selection of the polarity of the EXT TRIG signal. (A polarity selection procedure is given in the Maintenance section.
8842A Instruction Manual U806A, U806B, and a voltage divider (R804 and R805) provide gain which is selected for each range by the analog switches in U804. The configuration for each range is shown in Figure 5-17. (In this figure, the CMOS analog switches are represented by mechanical switches.) When U806A is not used, its non-inverting input is grounded by Q804. When U806B is not used, its non-inverting input is connected to the CURRENT SENSE line. 5-45.
static awareness A Message From Fluke Corporation Some semiconductors and custom IC's can be damaged by electrostatic discharge during handling. This notice explains how you can minimize the chances of destroying such devices by: 1. Knowing that there is a problem. 2. Leaning the guidelines for handling them. 3. Using the procedures, packaging, and bench techniques that are recommended. The following practices should be followed to minimize damage to S.S. (static sensitive) devices. 1.
5. USE STATIC SHIELDING CONTAINERS FOR HANDLING AND TRANSPORT. 8. WHEN REMOVING PLUG-IN ASSEMBLIES HANDLE ONLY BY NON-CONDUCTIVE EDGES AND NEVER TOUCH OPEN EDGE CONNECTOR EXCEPT AT STATIC-FREE WORK STATION. PLACING SHORTING STRIPS ON EDGE CONNECTOR HELPS PROTECT INSTALLED S.S. DEVICES. 6. DO NOT SLIDE S.S. DEVICES OVER ANY SURFACE. 9. HANDLE S.S. DEVICES ONLY AT A STATIC-FREE WORK STATION. 10. ONLY ANTI-STATIC TYPE SOLDERSUCKERS SHOULD BE USED. 11. ONLY GROUNDED-TIP SOLDERING IRONS SHOULD BE USED. 7.
Chapter 6 Maintenance Title 6-1. 6-2. 6-3. 6-4. 6-5. 6-6. 6-7. 6-8. 6-9. 6-10. 6-11. 6-12. 6-13. 6-14. 6-15. 6-16. 6-17. 6-18. 6-19. 6-20. 6-21. 6-22. 6-23. 6-24. 6-25. 6-26. 6-27. 6-28. 6-29. 6-30. 6-31. 6-32. 6-33. 6-34. Page INTRODUCTION.................................................................................. 6-3 PERFORMANCE TEST ........................................................................ 6-4 Diagnostic Self-Tests .................................................................
8842A Instruction Manual 6-35. 6-36. 6-37. 6-38. 6-39. 6-40. 6-41. 6-48. 6-59. 6-62. 6-63. 6-64. 6-65. 6-66. 6-67. 6-68. 6-69. 6-70. 6-71. 6-72. 6-73. 6-74. 6-75. 6-76. 6-77. 6-78. 6-2 EXTERNAL TRIGGER POLARITY SELECTION (Option -05 Only) 6-36 TROUBLESHOOTING ......................................................................... 6-36 Initial Troubleshooting Procedure...................................................... 6-36 Diagnostic Self-Tests .......................................................
Maintenance INTRODUCTION 6 WARNING THESE SERVICE INSTRUCTIONS ARE FOR USE BY QUALIFIED PERSONNEL ONLY. TO AVOID ELECTRIC SHOCK, DO NOT PERFORM ANY PROCEDURES IN THIS SECTION UNLESS YOU ARE QUALIFIED TO DO SO. 6-1. INTRODUCTION This section presents maintenance information for the 8842A. The section includes a performance test, a calibration procedure, troubleshooting information, and other general service information.
8842A Instruction Manual AC Calibrator Fluke 5700A and Fluke 5725A Minimum Required Accuracy (By Range) 1 2 2 Frequency Range 1, 10, 100 mV 1, 10, 100V 1000V 20 Hz – 30 Hz .1 + .005 .1 + .005 .12 + .005 30 Hz – 20 kHz .02 + 10 0.2 + .002 .04 + .004 20 kHz – 50 kHz .05 + 20 .05 + .005 .08 + .005 50 kHz – 100 kHz .05 + 20 .05 + .005 .1 + .01 1. ±(% of setting + µV) 2.
Maintenance PERFORMANCE TEST 6 To initiate the self-tests, press the SRQ button for 3 seconds. The TEST annunciator will then light up, and the 8842A will run through the analog tests in sequence. Each test number is displayed for about 1 second. The instrument can be stopped in any of the test configurations by pressing the SRQ button while the test number is displayed. Pressing any button continues the tests.
8842A Instruction Manual f6-01.wmf Figure 6-1. DC Calibration Connections Table 6-2. DC Voltage Test Displayed Reading STEP RANGE INPUT SLOW (V dc) MIN MEDIUM MAX MIN MAX MIN MAX 1 20 mV 0V (short) -0.0030 +0.0030 -0.0050 +0.0050 -0.030 +0.030 1 200 mV 0V (short) -00.003 +00.003 -00.005 +00.005 -00.03 +00.03 C 1 2V, 20V, 200V, 1000V 0V (short) -2 counts +2 counts -4 counts + 4 counts -3 counts +3 counts D 20 mV 10 mV +9.9963 +10.0037 +9.9943 +10.0057 +9.
Maintenance PERFORMANCE TEST 6-5. 6 AC Voltage Test (Option -09 Only) The following procedure may be used to verify the accuracy of the VAC function: 1. Ensure the 8842A is on and warmed up for at least 1 hour. 2. Select the VAC function and the slow (S) reading rate. 3. Connect the AC Calibrator to provide a voltage input to the HI and LO INPUT terminals. 4. (Low- and Mid-Frequency Test.
8842A Instruction Manual Table 6-4. High-Frequency AC Voltage Test STEP NUMBER RANGE 1 INPUT VOLTAGE FREQUENCY ERROR IN COUNTS 200 mV 0.010000V 50 kHz 2* 200 mV 0.010000V 3* 2V 4* TEST LIMITS (IN VOLTS) MIN MAX 169 09.831 mVAC 10.169 mVAC 100 kHz 350 09.650 mVAC 10.350 mVAC 0.10000V 100 kHz 350 0.09650 VAC 0.10350 VAC 20V 1.0000V 100 kHz 350 0.9650 VAC 1.0350 VAC 5* 200V 10.000V 100 kHz 350 09.650 VAC 10.350 VAC 6* 700V 100.00V 100 kHz 350 96.50 VAC 103.
Maintenance PERFORMANCE TEST 6 Table 6-5.
8842A Instruction Manual 6-8. AC Current Test (Option -09 Only) The following procedure may be used to test the mA AC function: 1. Ensure the 8842A is on and warmed up for at least 1 hour. 2. Select the mA AC function. 3. Connect the AC Current Source to provide a current input to the 2A and LO INPUT terminals.
Maintenance CALIBRATION 6 6-10. Basic Calibration Procedure The basic calibration procedure consists of the following four parts. These parts must be performed in the order shown. 1. Initial Procedure. 2. A/D Calibration. 3. Offset and Gain Calibration for each function and range. 4. High-Frequency AC Calibration (True RMS AC option only). Normally, it is recommended that the entire calibration procedure be performed. However, under some circumstances the earlier parts may be omitted.
8842A Instruction Manual f6-03.wmf Figure 6-3. Calibration Functions The following functions are inappropriate during calibration, and are therefore unavailable: • Offset • Autoranging • External Trigger • Front Panel Trigger • Front panel SRQ (Under local control) • Diagnostic self-tests 6-12. A/D CALIBRATION The A/D Calibration procedure calibrates the analog-to-digital converter for offset, gain and linearity.
Maintenance CALIBRATION 6 2. Each time the 8842A prompts you for a reference source, apply the requested source to the HI and LO INPUT terminals, and press the STORE button. When STORE is pressed, the numeric display field blanks while the 8842A performs the necessary calculations. (Do not change the reference source while the display is blank.) The 8842A then displays the next prompt. For reference, all prompts are shown in Table 6-8.
8842A Instruction Manual The A/D Calibration procedure is an iterative process. Each pass through the procedure uses the constants stored previously and improves them. Normally, one pass is adequate. However, if the calibration memory has been erased or replaced, or the A/D Converter has undergone repair, the A/D Calibration procedure must be performed twice.
Maintenance CALIBRATION 6 NOTE To use reference sources that differ from the prompted values, see Storing Variable Inputs later in this section. 4. After the last range is calibrated, the 8842A begins taking readings in the highest range so that you may verify its calibration. (The CAL annunciator remains on.) To verify the calibration for the other ranges, press the corresponding range button. (Pressing a function button begins the Offset and Gain Calibration procedure for that function.) 5.
8842A Instruction Manual 5. The calibration procedure is now completed. Exit the calibration mode by pressing the CAL ENABLE switch, and attach a calibration certification sticker over the CAL ENABLE switch. 6-15. Advanced Features and Special Considerations Table 6-11. High-Frequency AC Calibration Steps 1 2 STEP DISPLAYED PROMPT , A 100.0 mV AC B 1.000 V AC C 10.00 V AC D 100.0 V AC E 200.0 V AC 1. The display also indicates “U” to show that HF AC cal is selected. 2.
Maintenance CALIBRATION 6 6-17. CALIBRATING INDIVIDUAL RANGES During Offset and Gain and High-Frequency AC Calibration, it is possible to calibrate individually selected ranges. This feature does not apply to the mA DC and mA AC functions and is not permitted during A/D Calibration. To calibrate an individual range, proceed as follows: 1. Select the desired calibration procedure by pressing the appropriate function button (or press the HF AC button if High-Frequency AC Calibration is desired). 2.
8842A Instruction Manual 1. If you just completed the Offset and Gain or High-Frequency AC Calibration for an entire function (not just one range), the range buttons can be used to change ranges in order to verify all ranges were calibrated correctly. 2. If you just calibrated an individually selected range, pressing another range button begins the Offset and Gain Calibration procedure for the new range. 3. You can use the RATE button to verify the calibration at other reading rates.
Maintenance CALIBRATION 6 If ERROR 41 occurs, the most likely cause is that the reference input is incorrect (e.g., has the wrong polarity). If the input is in fact correct, refer to the Troubleshooting heading in this section. Table 6-13. Tolerance Limits CALIBRATION 1. A/D Calibration 2. Offset and Gain Calibration 3.
8842A Instruction Manual readings. (In remote calibration, the averaged value can be stored in the controller.) Record the value. 4. Select the "100Ω" output from the 5450A, and measure this value as in step 3. 5. Find and record the numerical difference between the values calculated in steps 3 and 4. This value will be used as the variable input for calibrating the 200Ω range in 2wire ohms. 6.
Maintenance CALIBRATION 6 Table 6-14. Commands Used During remote Calibration FRONT PANEL FEATURE CORRESPONDING COMMAND Display G2 Function Buttons F1 through F6 Range STORE COMMENTS Loads the calibration prompt into the output buffer. Not valid when the 8842A is taking verification readings. In the calibration mode, these select the Offset and Gain Calibration procedure for the corresponding funtion.
8842A Instruction Manual 1. In remote calibration, you can store a 16-character message in the calibration memory which can be read by the system controller. Possible uses include storing the calibration date, instrument ID, etc. 2. Although some buttons are ignored in local calibration (e.g., the AUTO button), the corresponding remote commands (e.g., R0) load the output buffer with an error message. 3. The calibration memory is erased differently. (This is explained later.) 4.
Maintenance CALIBRATION 6 6-24. TIMING CONSIDERATIONS Table 6-15.
8842A Instruction Manual The C0 command can take up to 22 seconds. If during this time the controller continues to send the 8842A more commands, the commands may fill up the 8842A’s input buffer. If this happens, errors will probably occur. You can avoid this problem by knowing when these commands are completed. There are three ways to determine this: 1. Monitoring the Cal Step Complete bit in the serial poll status register.
Maintenance DISASSEMBLY PROCEDURE 6 f6-05.wmf Figure 6-5. Example A/D Calibration Program 6-27. DISASSEMBLY PROCEDURE WARNING TO AVOID ELECTRIC SHOCK, REMOVE THE POWER CORD AND TEST LEADS BEFORE DISASSEMBLING THE INSTRUMENT. OPENING COVERS MAY EXPOSE LIVE PARTS. CAUTION To avoid contaminating the printed circuit assemblies (PCAs), handle the PCAs by their edges. Do not handle the areas of the PCAs that are not solder masked unless absolutely necessary. These areas must be cleaned if contaminated.
8842A Instruction Manual 6-28. Case Removal 1. Remove the grounding screw from the bottom of the case. Remove two rear bezel mounting screws. (See Figure 6-6A.) 2. While holding the front panel, slide the case and rear bezel off the chassis (See Figure 6-6B). (At this point, the rear bezel is not secured to the case.) f6-06_1.wmf Figure 6-6.
Maintenance DISASSEMBLY PROCEDURE 6 f6-06_2.wmf Figure 6-6.
8842A Instruction Manual f6-06_3.wmf Figure 6-6.
Maintenance DISASSEMBLY PROCEDURE 6 f6-06_4.wmf Figure 6-6.
8842A Instruction Manual 6-29. True RMS AC PCA Removal (Option -09 Only) The True RMS AC PCA should be removed by reversing the last three steps in Figure 809-1 (see Section 8). 1. Release the True RMS AC PCA from the chassis by pulling the four plastic latches upward (Figure 809-1E). 2. Raise the True RMS AC PCA slightly, and disconnect the red lead from the connector (J301) located on the Main PCA (Figure 809-1C). 3.
Maintenance DISASSEMBLY PROCEDURE 6 b. Unplug the ribbon cable from the Main PCA and lift out the LINE SET PCA. 9. Remove the push rod for the CAL ENABLE switch as follows (Figure 6-6H): a. While supporting the white plunger of the CAL ENABLE switch with a finger, pop the push rod off the switch plunger by pulling the push rod directly upward. b. Rotate the push rod 90 degrees toward the center of the instrument. c. Pull the push rod toward the rear panel and remove it. 10.
8842A Instruction Manual 6-32. Front Panel Disassembly 1. Holding the chassis vertically (with the front panel downward), remove the mounting screws from the four corners of the Display PCA (Figure 6-7A). 2. Holding the chassis vertically (now standing the instrument on the rear panel), pull the front panel off the chassis and set it aside (Figure 6-7B). 3. Remove the the display assembly (Display PCA, spacer matrix, and keypad) from the chassis as follows (see Figure 6-7C): a.
Maintenance REASSEMBLY PROCEDURE 6 NOTE When installing the Main PCA, guide the rear ribbon cable around the shield connected to the rear panel so that the cable is next to the side of the chassis. Make certain that the cable is not pinched between the shield and the Main PCA. a. Slide the Main PCA toward the rear panel, and position the power connector and fuse to fit through their respective openings in the rear panel. b.
8842A Instruction Manual f6-07.wmf Figure 6-7.
Maintenance REASSEMBLY PROCEDURE 6 f6-08.wmf Figure 6-8. Removing the Display Window CAUTION Make certain that the CAL ENABLE switch shaft is in the out (disabled) position after the CAL ENABLE push rod is installed. If the 8842A is switched on with the CAL ENABLE switch in the enabled position, the 8842A may require recalibration. 10. Position the slot in the lower edge of the Line Voltage Selection Switch PCA in the slot on the lower rear panel standoff.
8842A Instruction Manual WARNING TO AVOID ELECTRIC SHOCK, ENSURE THAT THE GROUNDING SCREW IS FIRMLY ATTACHED TO THE CASE BOTTOM. 6-34. INTERNAL FUSE REPLACEMENT CAUTION For fire protection, use exact fuse replacements only. The 8842A has an internal 3A 600V slow-blow fuse (F301) in series with the 2A input terminal. To replace this fuse, remove the case according to the disassembly instructions. The fuse is held in fuse clips on the Main PCA. Do not use makeshift fuses or shortcircuit the fuse holder.
Maintenance TROUBLESHOOTING 6 If the display lights up, perform the self-test by pressing the SRQ button for 3 seconds. (Remember, the input terminals must be disconnected from the test leads during the selftests. Otherwise, the 8842A may indicate errors are present.) The test numbers will appear consecutively. "ERROR" will appear on the display if a test should fail. The 8842A can be held in each of the test configurations by momentarily pressing the SRQ button. (Press any button to continue the tests.
8842A Instruction Manual Table 6-16. Overall State Table t6-16_1.
Maintenance TROUBLESHOOTING 6 Table 6-16. Overall State Table (cont) t6-16_2.
8842A Instruction Manual Table 6-17. Circuitry Tested by the Analog Self-Tests t6-17.wmf Some failures will cause many self-tests to fail. If this occurs, the fault is usually in the Track/Hold circuit, the A/D Converter, the Digital Controller circuit, or the Power Supply. Again, measure all of the power supply levels according to the limits specified in Table 6-23. The next step is to isolate the problem to a specific section.
Maintenance TROUBLESHOOTING 6 A failure in the instrument may cause the 8842A to display random patterns or nothing at all. Usually, analog circuit failures do not cause the display to go blank or display random patterns. The best place to start troubleshooting a "dead" instrument or an instrument with a non-functional display is to check the power supply with a voltmeter for proper levels and to use an oscilloscope to check the supplies for oscillations.
8842A Instruction Manual 6-39. Self-Test Descriptions Table 6-18. Self-Test Voltages TEST NUMBER TEST POINT VOLTAGE 1 TP803 ±5 mV dc 2 TP803 ±5 mV dc 3 TP803 ±5 mV dc 4 TP103 T/H output waveform for zero input (Figure 6-14) 5 TP302 ±5 mV dc 6 TP302 ±5 mV dc 7 TP302 +50 mV dc typical 8 TP302 +11.5V dc typical 9 TP302 +11.5V dc typical 10 TP302 +4.5V dc with possibly 1V ac (p-p) at 10 Hz 11 TP302 +4.5V dc with possibly 1V ac (p-p) at 10 Hz 12 TP302 +4.
Maintenance TROUBLESHOOTING 6 Configures the 8842A in the mA DC function and the slow reading rate, and measures the reading across the 0.1Ω current shunt. This test should be fairly immune to outside noise because the total driving impedance is typically less than 1 kΩ. The reading is not a perfect zero because of the offsets generated by charge injection of U302 and the T/H Amplifier (X10 configuration). • TEST 5: 200 VDC, Zero Configures the 8842A in the 200V dc range and slow reading rate.
8842A Instruction Manual These tests put the 8842A in the respective range of the 2-wire ohms function. They check that each range of the Ohms Current Source has enough compliance voltage to overload the dc front end. • TEST 15: 1000 VDC + X10 T/H + 20 MΩ Puts the Ohms Current Source in the 500 nA range. The resulting current through Z302 (the 10 MΩ input divider) causes a nominal divider output voltage of 50 mV. The T/H Amplifier is in X10; thus the A/D Converter sees 50 mV, or 5000 counts.
Maintenance TROUBLESHOOTING • 6 TEST 28: External Program Memory (U222) A two-byte check sum is calculated over the entire 4K External Program Memory and compared with the checksum bytes at the end of that memory. A special add and shift algorithm minimizes the possibility of double errors cancelling. If something is wrong with the External Program Memory, ERROR 28 is displayed.
8842A Instruction Manual programmed as inputs to prevent contentions between them and the outputs from other ICs which drive them. Data coming into all µC inputs (except pin 38) is ignored. NOTE If the A/D IC (U101) is working properly, its watchdog timer briefly interrupts all of the In-Guard Troubleshooting Mode signals every 1.5 sec for a period of about 0.2 sec. (The signals are then re-established.) If this occurs, the main counter in U101 and its watchdog timer are operating correctly.
Maintenance TROUBLESHOOTING 6 1. Power supplies: +5V dc at U202-1; 0V dc U202-11. 2. µC clock output: 8 MHz at U202-2,-3. 3. Trigger line U202-40 (TP201): Square wave, 50% duty, low 0V, high 3.8V (nominal). The period of the trigger signal should be 12.500 ms for 60 Hz line. 4. Interrupt from A/D (U202-39): Normally low, duration 48 µs occurs approximately 5450 µs after falling edge of trigger signal on TP201 (U202-40). 5. Guard-crossing test pattern (U202-4): Waveform C (see Figure 6-10). 6.
8842A Instruction Manual 16, -18, -21, -25 are the same as Waveform B. The waveforms should be interrupted every 1.5 sec for 0.2 sec due to interrupts from the watchdog timer. (Note: XU222 pins refer to a 28-pin socket.) 6-45. Calibration Memory (U220) Sync on U219-3. Verify that U220-1, -3, -5, -7, -10, -13, -15, -17, -22 are the same as Waveform A (U219-3). Verify that U220-2, -4, -6, -8, -9, -11, -14, -16, -19, -23 are the same as Waveform B. The waveforms should be interrupted every 1.5 sec for 0.
Maintenance TROUBLESHOOTING 6 possible to freeze the display, it should still be possible to observe the waveforms at U215, U213, U221, and U211 as described in the following paragraphs. To freeze the display, turn off the instrument, press the POWER switch and within 1 second press the SRQ button. If all is well, all display segments will light and remain lit. Do not press any other buttons as that will release the display, allowing the instrument to resume its normal power-up sequence.
8842A Instruction Manual Check for the same waveforms at outputs U215-11 through U215-18. (However, the high level should be approximately 30V.) If these waveforms are OK, then strobe decoder U213 and display control U212 are OK in this regard. 6-51. 3-to-8 Strobe Decoder (U213) Check for strobe waveforms 0-7 on U213-4, -5, -6, -7, -9, -10, -11, -12. Reference U2134 for STROBE ZERO. Check for strobe decoder inputs SL0, SL1, SL2 on U213-1, -2, -3 respectively. 6-52.
Maintenance TROUBLESHOOTING 6 6-56. Hex Inverter (U221) Check that U221-5 is the same as STROBE ZERO and that U221-6 is STROBE ZERO inverted. 6-57. Quad OR Gate (U211) Check U211-6 for 0.2 us pulses, normally high, in two groups of 3 and 15, group widths: 50 and 100 us, group spacing: 10 ms (in fast reading rate). Check U211-8 for 0.4 us pulses, normally high, groups of hundreds, group widths: 3.5-4 ms, group spacing: about 8 ms (variable). 6-58.
8842A Instruction Manual Table 6-20. Analog Control Devices DEVICE REF. DES.
Maintenance TROUBLESHOOTING 6 Table 6-21. Analog Control Logic States t6-21.wmf Next move to U305-5 and repeat.
8842A Instruction Manual If the instrument is not in the slow reading rate, it gives the following pattern at U305-5: 000000 00000 000000 0000000 000 Next move to U305-7 and repeat. The pattern at U305-7 will be: 000000 00000 000000 1111111 000 6-61. Evaluating Dynamic Signals The procedure for evaluating the dynamic signals is only slightly more involved. For example, consider U302-7 in Table 6-21. At the right end of that row the table says to sync on U302-3. The sync pulse is negative-going.
Maintenance TROUBLESHOOTING 6 Table 6-22. DC Scaling and Track/Hold Supply Voltages PIN OR DEVICE SUPPLY VOLTAGE PIN OR DEVICE SUPPLY VOLTAGE U301-6 +5V U303-20 +7.5V U301-10 0V U303-11 -8.2V U301-20 +7.5V U304-4 -8.2V U301-11 -5V U304-7 +7.5V U302-6 +5V U305-3 +5V U302-10 0V U305-12 -5.5V(Nom)* U302-20 +7.5V U307-4 -15V U302-11 -5V U307-7 +15V U303-6 +5V Q305,c +30V U303-10 0V Q306,c -30V *With 0V input.
8842A Instruction Manual 6-63. Track/Hold Troubleshooting If a problem is suspected in the Track/Hold (T/H) circuit, first check the power supply voltages of all active components. (See Table 6-22.) Next, check the T/H output waveform at TP103 with an oscilloscope. Set the 8842A to the VDC function and 2V dc range, apply +1V dc across the HI and LO INPUT terminals, and trigger the scope from the falling edge of line not-TR (TP201). The waveform should look like that in Figure 6-13.
Maintenance TROUBLESHOOTING 6 f6-13.wmf Figure 6-13. Typical Output Waveforms for Track/Hold Circuit (TP103) To test whether the Ohms Current Source is actually being sourced out the HI and LO OUTPUT terminals, select the 20 kΩ range and the 2-wire ohms function, connect a 10 kΩ resistor across the HI and LO INPUT terminals, and measure the voltage across this resistor with another voltmeter. There should be a 1V drop across the resistor.
8842A Instruction Manual If the ohms functions do not work in any range, check the supplies at U401 (+/-15V), U404 (+30V and -5V), U402 (+15V, +5V, and 0V), and U403 (+15V, +5V, and 0V), and check the -7V reference at R416. Also, test the Ohms Protection circuitry as follows: Select the 20 kΩ range and 2-wire ohms function, connect a 10 kΩ resistor to the HI and LO INPUT terminals, and bypass the protection circuitry by connecting the emitter of Q402 to the junction of R410 and R309.
Maintenance TROUBLESHOOTING 6 6-66. A/D Converter Troubleshooting If there is a failure of the A/D Converter, all power supply levels should be checked at the op amps (U102 and U103) and the A/D IC (U101). The A/D Converter has a total of seven supplies: +15V, -15V, +5V, +7.5V, -8.2V, +7.00000V, and -7.00000V. All supplies should be within 5% of their nominal values except for the +7.00000V and 7.00000V reference supplies, which should be within +/-1000 ppm and +/-250 ppm respectively.
8842A Instruction Manual f6-15.wmf Figure 6-15. Waveforms at U101-24 and U101-25 f6-16.wmf Figure 6-16. Typical Bus Data Line Waveform The waveform at the storage capacitors can often be used to locate leakage problems. The leakage can be due to contamination on the Main PCA or to defective switches in U101. Figure 6-15 shows the waveforms across storage capacitors C102 and C103 (U101-24 and U101-25, respectively) for a specific input.
Maintenance TROUBLESHOOTING 6 problem between the A/D Converter and the In-Guard µC can cause erroneous or noisy readings or offsets. Similar problems may be caused by a failure of the Calibration Memory (U220) or by bad A/D calibration constants. (To check for bad A/D calibration constants, clear the calibration memory.) Readings at the A/D Converter can be determined by interpreting the waveform at the DAC output (TP102). Waveforms at TP102 for several input levels are shown in Figure 6-18.
8842A Instruction Manual f6-17.wmf Figure 6-17. Waveforms at TP102 for Several Inputs on 2V DV Range Since power supply problems can produce symptoms in many different sections of the instrument, the first step in troubleshooting any problem should usually be a quick check of the power supplies. For each power supply (TP801-TP806), check the level with a voltmeter and check for ripple with an ac-coupled oscilloscope. The dc voltages should be within the limits given in Table 6-23.
Maintenance TROUBLESHOOTING 6 f6-18.wmf Figure 6-18. Calculating the A/D Reading From TP102 Waveform Table 6-23. Power Supply Voltages TEST POINT LIMITS (in volts) MINIMUM MAXIMUM +5V 4.75 5.25 +7.5V 7.00 7.87 +15V 14.25 15.75 +30V 28.45 31.55 -8.2 -8.61 -7.60 -15V -15.75 -14.25 -30V -31.55 -28.45 If a supply is too low, there are a number of possible causes. First check the input to the affected regulator.
8842A Instruction Manual The True RMS AC PCA, if installed, uses +5V and +/-15V. If there is a problem with one of those supplies, first disconnect the True RMS AC PCA. If the problem goes away, troubleshoot the True RMS AC PCA using the procedure given later in this section. With most power supply problems, the output voltage is too low or too high. More subtle problems that may be encountered include high ripple or oscillation.
Maintenance TROUBLESHOOTING 6 f6-19.wmf Figure 6-19. Option -05 Service Position Table 6-24. Diagnostic Modes SWITCHES A3 A2 A1 CONFIGURATION 1 0 1 Static, odd-port bits = 1, even-port bits = 0 1 1 1 Static, odd-port bits = , even-port bits = 1 1 X 0 Dynamic 0 X x Read/Write NOTES: • “x” means switch setting does not matter. • “Static” means the Out-Guard µC I/O port bits programmed as outputs are driven to a constant logic 1 or 0 level (as determined by switch A2).
8842A Instruction Manual Table 6-25.
Maintenance TROUBLESHOOTING 6 4. Position the True RMS AC PCA vertically as shown in Figure 6-20 and latch it in place by pressing the bottom two nylon latches into the specially provided mounting supports on the chassis. 5. Connect the Main PCA ac take-off point (stud connector W301) to the True RMS AC PCA input (the stud connector labeled AC IN) with a 6-inch jumper (E-Z-Hook 2046W-S or equivalent). 6-73.
8842A Instruction Manual f6-20.wmf Figure 6-20. Option -09 Service Position If the signal at the input to U801A (pin 5) is incorrect, U804 may be defective, or the switch codes may be wrong. If the latter problem is suspected, refer to Table 6-28 and test the control lines to U804 (U804-1, 8, 9, 16). If a logic error is found, it may be due to excessive loading or a faulty data latch (U803), or other cabling or main-board digital problems.
Maintenance TROUBLESHOOTING 6 Table 6-28. Truth Table for U804 and K2 RANGE PIN OR DEVICE U804-1 U804-8 U804-9 U804-16 K2 2000 mA 1 0 1 1 0 200 mV 1 0 0 1 0 2V 1 1 1 0 0 20V 0 1 1 1 0 200V 1 1 1 0 1 700V 0 1 1 1 1 NOTE: For U804, logic 0 = switch on. Logic 1 is >2.4V; logic 0 is <0.8V. If the signal at TP802 is correct but the output signal (TP803) is incorrect, the rms converter is probably the source of the problem.
8842A Instruction Manual It is safe to force one control line at a time high (+5V) or low (0V) to test the individual switches in U808. (The on resistance of switches in U808 should be less than 500Ω; the off resistance should be greater than 10 MΩ.) Forcing the control lines high or low should cause the reading to change when the voltages in Table 6-27 are applied to the input terminals at 100 kHz. If only certain ranges cannot be calibrated, refer to Table 626 to find the suspected stage. 6-75.
Maintenance INTERNAL CLEANING 6 6-78. Cleaning After Soldering CAUTION T.M.C. Cleaner and similar products can can attack the nylon latches and other plastic pieces. f6-21.wmf Figure 6-21. Guard Crossing Test Waveforms If a PCA has been soldered, it should first be cleaned with SPRAYON T.M.C Cleaner (rosin flux remover) or equivalent. The PCA should then be cleaned with water as described above.
8842A Instruction Manual 6-72
Chapter 7 List of Replaceable Parts Title 7-1. 7-2. 7-3. 7-4. 7-5. Page INTRODUCTION................................................................................7-3 HOW TO OBTAIN PARTS.................................................................7-3 MANUAL STATUS INFORMATION................................................7-3 NEWER INSTRUMENTS...................................................................7-4 SERVICE CENTERS........................................................................
8842A Instruction Manual 7-2
List of Replaceable Parts INTRODUCTION 7 7-1. INTRODUCTION This section contains an illustrated list of replaceable parts for the 8842A. Parts are listed by assembly; alphabetized by reference designator. Each assembly is accompanied by an illustration showing the location of each part and its reference designator.
8842A Instruction Manual 7-4. NEWER INSTRUMENTS Changes and improvements made to the instrument are identified by incrementing the revision letter marked on the affected pca. These changes are documented on a supplemental change/errata sheet which, when applicable, is included with the manual. 7-5. SERVICE CENTERS A list of service centers is located at the end of this section. NOTE This instrument may contain a Nickel-Cadmium battery. Do not mix with the solid waste stream.
List of Replaceable Parts SERVICE CENTERS 7 Manual Status Information REF OF OPTION NO. ASSEMBLY FLUKE PART NO. REVISION LEVEL A1 A2 05 09 Main PCA Display PCA IEEE-488 Interface PCA True RMS AC PCA 759365 728873 879267 759266 BE __ D N Table 7-1.
8842A Instruction Manual f7-01_1.wmf Figure 7-1.
List of Replaceable Parts SERVICE CENTERS 7 f7-01_2.wmf Figure 7-1.
8842A Instruction Manual f7-01_3.wmf Figure 7-1.
List of Replaceable Parts SERVICE CENTERS 7 f7-01_4.wmf Figure 7-1.
8842A Instruction Manual Table 7-2.
List of Replaceable Parts SERVICE CENTERS 7 Table 7-2.
8842A Instruction Manual Table 7-2. A1 Main PCA (cont) Description Reference Designator R413 R414 R416 R601 RV301,RV401-404 RV601 S201 S601 T201,T202 T601 TP101-105,TP201, TP202,TP204-207, TP301-304,TP401, TP403,TP601-605, TP607-609 U102,U702 U103 U201 0203 U204,U305 U208 U211 0213 U215,U217,U218 0216 U219 0221 U301-303,U402 U304 0306 U307 0401 U403 U404 VR601 VR602 VR603 VR604 VR605 W1,W8 W2,W9 W5 W6 W10 W11 W12 XU101,XU102, XU212 XU220 XU222 Y201 Z101 Z301,Z303 Z302 Z304,Z402 Z401 Z702 RES,MF,4.
List of Replaceable Parts SERVICE CENTERS 7 f7-03.wmf Figure 7-2.
8842A Instruction Manual Table 7-3.
List of Replaceable Parts SERVICE CENTERS 7 f7-03.wmf Figure 7-3.
8842A Instruction Manual Supply Codes for Manufacturers supply_1.
List of Replaceable Parts SERVICE CENTERS 7 Supply Codes for Manufacturers (cont) supply_2.
8842A Instruction Manual service_1.wmf Figure 7-4.
List of Replaceable Parts SERVICE CENTERS 7 service_2.wmf Figure 7-4.
8842A Instruction Manual 7-20
Chapter 8 Options and Accessories Title 8-1. 8-2. 8-3. 8-4. 8-5. 8-6. 8-7. 8-8. 8-9. 8-10. 8-11. 8-12. Page INTRODUCTION.................................................................................. 8-3 ACCESSORIES ..................................................................................... 8-4 Rack-Mount Kits (Y8834, Y8835 and Y8836).................................. 8-4 Shielded IEEE-488 Interface Cables (Y8021, Y8022, and Y8023)... 8-4 Replacement Test Leads (TL70A) .....................
8842A Instruction Manual 8-2
Options and Accessories INTRODUCTION 8 8-1. INTRODUCTION A number of options and accessories are available which can enhance the 8842A’s capabilities and increase operator safety. The accessories are summarized in Table 8-1 and described in the following paragraphs. The options are summarized in Table 8-2 and described in the following subsections. Table 8-1.
8842A Instruction Manual 8-2. ACCESSORIES Accessories include a variety of rack-mounting kits, cables, test leads, and probes. The accessories include installation and/or operating instructions. 8-3. Rack-Mount Kits (Y8834, Y8835 and Y8836) The rack-mount kits allow the 8842A to be mounted in standard 19-inch rack panels. The Y8834 kit allows the 8842A to be mounted either on the left or the right. The Y8835 kit allows two 8842As to be mounted side-by-side.
Options and Accessories ACCESSORIES 8 8-10. Current Shunt (80J-10) The 80J-10 current shunt extends ac or dc current measurement up to 10A continuous, or to 20A for one minute without overheating. 8-11. Current Probes (Y8100, Y8101, 80i-400 and 80i-600) The current probes extend the ac and dc current measurement range. The Y8100 current probe uses the Hall effect to measure dc or ac current up to 200A (in two ranges) without electrical contact.
8842A Instruction Manual 8-6
Chapter 805 Option –05 IEEE-488 Interface Title 805-1. 805-2. 805-3. 805-4. 805-5. 805-6. 805-7. INTRODUCTION................................................................................ CAPABILITIES ................................................................................... EXTERNAL CONTROLS................................................................... INSTALLATION ................................................................................. PROGRAMMING INSTRUCTIONS..................
8842A Instruction Manual 805-2
Option –05 IEEE-488 Interface INTRODUCTION 805-1. 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. 805-2.
8842A Instruction Manual 3. Disconnect the ribbon cable from the plastic rear panel insert by pulling the tabs on either side of the ribbon cable connector outward. Pull the ribbon cable directly toward the front panel (Figure 805-1C). 4. Remove the rear panel insert by releasing the two snap tabs inside the instrument (Figure 805-1D). NOTE The connection on the rear panel insert is used for factory calibration only. The connector is electrically isolated from all measuring circuitry. 5.
Option –05 IEEE-488 Interface LIST OF REPLACEABLE PARTS f805-1_1.wmf Figure 805-1.
8842A Instruction Manual f805-1_2.wmf Figure 805-1.
Option –05 IEEE-488 Interface LIST OF REPLACEABLE PARTS Table 805-1.
8842A Instruction Manual f805-2.wmf Figure 805-2.
Chapter 809 Option –09 True RMS AC Title 809-1. 809-2. 809-3. 809-4. 809-5. Page INTRODUCTION.................................................................................. 809-3 INSTALLATION ................................................................................... 809-3 OPERATING INSTRUCTIONS............................................................ 809-4 MAINTENANCE................................................................................... 809-4 LIST OF REPLACEABLE PARTS .......
8842A Instruction Manual 809-2
Option –09 True RMS AC INTRODUCTION 809-1. INTRODUCTION The True RMS AC option gives the 8842A the ability to make ac voltage and current measurements. The ac functions are selected with the front panel VAC and mA AC buttons, or by remote commands if the IEEE-488 Interface option is installed. Specifications for Option -09 are shown in Section 1, Table 1-1. 809-2. INSTALLATION The True RMS AC option is contained on a single, easy-to-install printed circuited assembly (PCA).
8842A Instruction Manual 809-3. OPERATING INSTRUCTIONS For operating instructions, refer to Section 2. For ac measurement considerations, refer to Section 4. 809-4. MAINTENANCE All service information regarding Option -09 is contained in Section 6. The theory of operation is contained in Section 5. 809-5. LIST OF REPLACEABLE PARTS A list of replaceable parts for the True RMS AC printed circuit assembly (PCA) is given in Table 809-1. Refer to Section 7 for ordering information.
Option –09 True RMS AC LIST OF REPLACEABLE PARTS f809-1.wmf Figure 809-1.
8842A Instruction Manual Table 809-1. Option -09 True RMS AC PCA t809-1.
Option –09 True RMS AC LIST OF REPLACEABLE PARTS f809-2.wmf Figure 809-2.
8842A Instruction Manual 809-8
Chapter 9 Schematic Diagrams 9-1
8842A Instruction Manual 9-2
Schematic Diagrams 9 f9-01_1.wmf Figure 9-1.
8842A Instruction Manual f9-01_2.wmf Figure 9-1. Main PCA, DC Scaling and F/R Switch (cont.
Schematic Diagrams 9 f9-02_1.wmf Figure 9-2.
8842A Instruction Manual f9-02_2.wmf Figure 9-2. Main PCA, A/D Converter (cont.
Schematic Diagrams 9 f9-03_1.wmf Figure 9-3.
8842A Instruction Manual f9-03_2.wmf Figure 9-3. Main PCA, Ohms Current Source (cont.
Schematic Diagrams 9 f9-04_1.wmf Figure 9-4.
8842A Instruction Manual f9-04_2.wmf Figure 9-4. Main PCA, Digital (cont.
Schematic Diagrams 9 f9-05_1.wmf Figure 9-5.
8842A Instruction Manual f9-05_2.wmf Figure 9-5. Main PCA, Power Supply (cont.
Schematic Diagrams 9 f9-06_1.wmf Figure 9-6.
8842A Instruction Manual f9-06_2.wmf Figure 9-6. Display PCA (cont.
Schematic Diagrams 9 f9-07_1.wmf Figure 9-7.
8842A Instruction Manual f9-07_2.wmf Figure 9-7. IEEE-488 Interface PCA (cont.
Schematic Diagrams 9 f9-08_1.wmf Figure 9-8.
8842A Instruction Manual f9-08_2.wmf Figure 9-8. IEEE-488 Interface PCA, Option –08 (cont.