FLUKE. For the benefit and convenience of its customers, Fluke Corporation (luke) has reproduced this copy of a manual which is no longer in Production. This manual has not been edited or updated since the revision date shown on the lower left hand comer of the frst page Fluke will not be liable for any claims, losses or damages of any kind incurred by any user arising from use of this manual. 8840A Digital Multimeter Instruction Manual PN 879304 December 1991 Rev. 3, 5/97 (© 1991, 1994,1997 Fluke Corporation, Al rights rserved. Printed in U.S.A, All prosuct namos ae Wasemares of het respective compancs,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 teplacement 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 repaid 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 594MULTIMETER SAFETY The Fluke 8840A Digital Multimeter has been designed and tested according to IEC Publication 348. Safety Requirements for Electronic Measuring Apparatus. This manual contains information and warnings which must be followed to ensure safe operation and retain the meter in safe condition, Use of this equipment in a manner not specified here in may impair the protection provided by the equipment, ‘Some common international electrical symbols used in this manual are shown below. OFF over DRvGEROUS Sinton rOsON vovrace (ON (power) |_| Sifetocmon | se | esrmencuno AGALTERNATING SE mPUNATON | Soren AN | Wis SEE nana Fon ooomecrcunmenr | ZA SEEMANUALFOR wnronuarioN ETHER OG On AC Before using the meter, read the following safety information carefully. In this manual, “WARNING,” is reserved for Conditions and actions that pose hazard (s) to the user; "CAUTION," is reserved for conditions and actions that may damage your meter. + Avoid working alone, Follow all safety procedures for equipment being tested. * Inspect the test leads for damaged insulation or exposed metal. Check test lead continuity. Damaged leads should be replaced + Be sure the meter is in good operation condition. + Select the proper function for your measurement. * To avoid electrical shock, use caution when working above 60V de or 25V ad RMS. + Disconnect the live test lead before disconnection the common test lead. + Disconnect the power and discharge high-voltage capacitors before testing in k® * When making a current measurement, turn the circuit power off before connecting the meter in the circuit. * Check meter fuses before measuring transformer secondary or motor winding current. (See Section 6, “MAINTE- NANCE.") An open fuse may allow high voltage build-up, which is potentially hazardous. + Use clamp-on probes when measuring circuits exceeding 2 amps.SECTION GUIDE Introduction and Specifications ....... Operating Instructions ................ Remote Programming ................ Measurement Tutorial ................ Theory of Operation Maintenance ....... List of Replaceable Parts .............. Options and Accessories .............. Schematic Diagrams IndexTable of Contents SECTION TITLE PAGE 1 Introduction and Specifications. . 341. INTRODUCTION. 3-2. THE 8840A DIGITAL MULTIMETER . 13. OPTIONS AND ACCESSORIES. 1-4. SPECIFICATIONS. : 2 Operating instructions...........0c000. 2. INTRODUCTION. a INSTALLATION . 24 Installing the Powe 21 Connecting to Line Power. 24 Adjusting the Handle . 24 Rack Mounting Kits 2 OPERATING FEATURES . 22 Power-Up Features ..... 22 Front and Rear Panel Features . 22 Display Features . 5 23 Error Messages 23 Overrange Indication. 23 Diagnostic Self-Tests - 27 27 27 27 27 27 EXTERNAL TRIGGER MODE. 27 Reading Rates and Noise Rejection . 29 Automatic Setting Time Delay....... 29 Extemal Trigger Input (Option -05 Only). 29 Sample Complete Output (Option -05 Onis). 29 MAKING MEASUREMENTS 29 Input Overload Protection Limits | 29 Measuring Voltage and Resistance 2-10 Measuring Current. . 2:10 ‘Current Fuse Protection - + 210 Offset Measurements. 210 EXTERNAL CLEANING 241Table of Contents SECTION Remote Programming . 331, 337. 349, 351. 3:52, 353. 3:54, 355. 357. INTRODUCTION. CAPABILITIES ..... BUS SET-UP PROCEDURE |... : AN OVERVIEW OF REMOTE OPERATION ‘A NOTE ABOUT EXAMPLES. DEVICE-DEPENDENT COMMAND SET. Bn (Offset Commands). Cn (Calibration Commands). . Dn (Display Commands) . Fa (Function Commands) Get Commands . GO (Get Instrument Configuration G1 (Get SRO Mask) . G2 (Get Calibration Prompt). G3 (Get User-Defined Message G4 (Get Calibration Status) G5 (Get TAB Status) . G6 (Get YW Status) - G7 (Get Error Status). G8 (Get Instrument Identification) N (Numeric Entry Command)... Put Commands. Pl (Put SRQ Mast)... P2 (Put Calibration’ Value) . P3 (Put User-Defined Message) ‘Sn (Reading Rate Commands) . Ta (Trigger Mode Commands) - ‘Wn (Terminator Commands) ‘XO (Clear Error Register Command) .- Yn (Suffix Commands) 20 (Self-Test Command) * (evice-Clear Command) .. 2 Single-Trigger Command) . INPUT SYNTAX. . Definitions ..... Input Processing ‘Syntax Rules OUTPUT DATA . Loading Output ‘Types of Output Data... Numeric Data and Error Messages MEASUREMENT DATA .. OVERRANGE INDICATION ERROR MESSAGES. ‘The Serial Poll Register. ‘The SRQ Mask... INTERFACE MESSAGES . ‘Address Messages Universal Commands . Addressed Commands . TALK-ONLY MODE REMOTE CALIBRATION . .Table of Contents ‘SECTION TMLE PAGE 3-58. TIMING CONSIDERATIONS . . 3:59. IMMEDIATE MODE COMMANDS. 3-60. EXAMPLE PROGRAMS........ 321 4 Measurement Tutorial ... sees OA 41, INTRODUCTION. DC_VOLTAGE MEASUREMENT . Circuit Loading Error. Input Bias Current Eror RESISTANCE MEASUREMENT . 2-Wire Ohms... Correcting for Test Lead Resistance in 2-Wire Ohms - 4-Wire Ohms. Applications of the Ohms Functions . TESTING DIODES ........ TESTING ELECTROLYTIC CAPACITORS . A PRECISION CURRENT SOURCE 413. DC CURRENT MEASUREMENT ........ 4-14. REDUCING THERMAL VOLTAGES ..... 415. AC VOLTAGE AND CURRENT MEASUREMENT. . 416. True RMS Measurement .... 417. Waveform Comparison 418. Crest Factor... 419. AC-Coupled AC Measurements. 4-20. Combined AC and DC Measurements. 421... Bandwidth... 422. Zero-Input VAC Exror 5 Theory of Operation. seeeee BA 3-1. INTRODUCTION. 5-2. OVERALL FUNCTIONAL DESCRIPTION. 5 5. 3. DETAILED CIRCUIT DESCRIPTION. . 4. DC SCALING .. 55. VDC Scaling 5 5-6. VDC Protect + 54 5-7. mA DC Scaling + 54 5-8. Analog Filter 54 59. TRACK/HOLD CIRCUIT. 54 5-10. Track Configuration 54 S-11. Settling Configuration 54 5-12. Hold Configuration 54 5-13. __Pre-Charge Configurati 54 5:14. PRECISION VOLTAGE REFERENCE | 54 5-15. OHMS CURRENT SOURCE... se 55 5-16. OHMS PROTECTION . 55 5-17. OHMS FUNCTIONS. 58 5-18. 2-Wire Ohms. - 58 5-19. 4-Wire Ohms. 58 5-20. A/D CONVERTER 1 59 5-21. Timing/Data Cont + S41 5-22. Precision DAC... S12 523. AD Amplifier... S12 5-24, Bootstrap Supplies... 542 5:25. DISPLAY...... 5-12 5-26. KEYBOARD. 513 5-27. DIGITAL CONTROLLERTable of Contents SECTION TE PAGE 5-28. Im-Guard Microcomputer. . $13 5-29. Function and Range Control S45 5:30. AD Contol and Computation 545 5-31. Calibration Correction... 545 532 545 5-33. 5-15 534, 545 5:35. 55 5:36. POWER SUPPLY «00.1... 547 5-37. IEEE-488 INTERFACE (OPTION -05) 58 5:38. Out-Guard Microcomputer ......... 548 5-39. Guard Crossing . 5-40. Bus Interface Circuitry S-41. Signal Condit 5-42, _IEEE-488 Imerface Power S 5-3. TRUE RMS AC (OPTION -09) . 5-44. VAC Sealing... ese 5-45. mA AC Scaling. 5-46. Frequency Response Trimming 5-47. True RMS AC icDC Conversion... Maintenance. 61. INTRODUCTION. . 61 62 PERFORMANCE TEST 61 63. Diagnostic Self-Tess. 61 6-4. DC Voltage Test 61 SSAC Voge Test (Option 29 Oaly 63 66. Resistance Test . 64 67. DC Curent Test 65 8. 66 69, 66 6-10. 66 ei. 67 12. ‘AID CALIBRATION... 67 63. OFFSET AND GAIN CALIBRATION .- 67 6-14. HIGH-FREQUENCY AC CALIBRATION 69 6-15. Advanced Features and Special Considerations 6-10 6-16. ‘STORING VARIABLE INPUTS . 6-10 617. CALIBRATING INDIVIDUAL RANGES. 6-10 618. VERIFYING CALIBRATION... 6A 6-19. ERASING CALIBRATION MEMORY . on 620. TOLERANCE CHECK .. + 62 621. ‘AC CALIBRATION AT OTHER FREQUENCIES. . 612 62. ‘OPTIMIZING USE OF THE 5450A, + 612 623. Remote Calibration . 63 6m. TIMING CONSIDERATIONS |. 14 625. REMOTE ERASURE. . + 61S 626. EXAMPLE CALIBRATION PROGRAM . + 616 627. DISASSEMBLY PROCEDURE : 616 628. 2 617 629. True RMS AC PCA Removal (Option -09) 2 647 S30. TEEE-G9 Inerace PCA Removal Option -05 Oa) + 617 631. Main PCA Removal. 2 647 632. __ Front Panel Disassembly + 622 633. REASSEMBLY PROCEDURE... + 62 6-3. INTERNAL FUSE REPLACEMENT | + 624 635. EXTERNAL TRIGGER POLARITY SELECTION (Option -05 Only) . + 625Table of Contents SECTION 635. 6.36. 637. 638. 639. 641. mM. 12. 73. 14, 15, Options and Accessories... 8. 82, 83, 8, of Replaceable Parts.......... TE EXTERNAL TRIGGER POLARITY SELECTION (Option -05 Only) ...... ‘TROUBLESHOOTING. - Initial Troubleshooting Procedure Diagnostic Self-Test : Self-Test Descriptions. Digital Controller Troubleshooting IN-GUARD MICROCOMPUTER S¥3 In-Guard Microcomputer ..... Address Latch (U219) Extemal Program Memory (XU222) - Calibration Memory (U220) Relay Buffer (U201), 3.10-8 Chip Select Decoder ua. ep DISPLAY SYSTEM.. Display Control (U212). 8-Bit Digit Driver (U215)... 3.t0-8 Strobe Decoder (U213) . Bit Segment Driver (U217 ab Digit Driver (U218)... Hex Inverter (U208). Hex Invener (U221). Quad OR Gate (U221)". Evaluating Static Signals. Evaluating Dynamic Signals .. DC Scaling Troubleshooting ... TrackHold Troubleshooting . Ohms Current Source Troubleshooting, Precision Voltage Reference Troubleshooting . AMD Convener Troubleshooting... Power Supply Troubleshooting .. TEEE-488 Interface Tetooing (Orion 5). SERVICE POSITION DIAGNOSTIC PROGRAM... ‘True RMS AC Troubleshooting (Option ®). SERVICE POSITION ‘MAJOR PROBLEMS. ‘MORE OBSCURE PROBLEMS Guard Crossing Troubleshooting INTERNAL CLEANING... ‘Cleaning Printed Circuit Assemblies, Cleaning After Soldering . INTRODUCTION... I HOW TO OBTAIN PARTS... MANUAL STATUS INFORMA\ ‘NEWER INSTRUMENTS... SERVICE CENTERS... INTRODUCTION . ACCESSORIES. Rack-Mount Kits (¥8&34, ¥8835 and Y8#36). Shielded IEEE-488 Interface Cables (Y8021, Y8022, and Y8023) PAGE 625 625 6-29 6:29 631 631 632 633 633 633 633 634 634 634 634 634 634 634 634 634 634 635 635 635 6.36 636 638 638 639 639Table of Contents SECTION TITLE PAGE Replacement Test Leads (TL70A). Deluxe Test Lead Kits (Y8134) . Slim-Flex Test Leads (8140) ‘Temperature Probes (80T-150U 89. RF Probes (8SRF and 83RF) . 8-10. Current Shunt (805-10). : 8-11. Current Probes (Y8100, Y8101, 80i-400 and 801-600) 5 8-12. High Voltage Probes (80K-6 and 80K-40) . Option -05 IEEE-488 Interface . ‘Option -09 True RMS AC.. ‘Schematic Diagrams. ° 88 INDEX619. 6-22. 805-1. . Error Numbers Which Are Displayed When Commands Are Not Valid 5. Overall State Table. . . Circuitry Tested by the Analog Self-Tests . |. Analog Control Des List of Tables TITLE Specifications Error Codes... : Input Overload Limits . Status Data. . Numeric Output Data Format...” Immediate-Mode Commands for Vari ASCIIEEE Std 488-1978 Bus Codes........ Ohms Test Current... - ‘Sample Rates and Reading Rates. Recommended Test Equipment . DC Voltage Test.. Low- and Mid-Frequency AC Voltage Test. High Frequency AC Voltage Tes. Resistance Test DC Current Test AC Current Test. AD Calibration Steps... AID Calibration Verification Test Offset_ and Gain Calibration Steps . High-Frequency AC Calibiation Steps . Prompts When Calibrating Individual Ranges. . Tolerance Limits - Commands Used During Remote Calibration Self-Test Voltages Keyboard Wiring. Analog Control Logie States. DC Scaling and Track/Hold Supply Votes Power Supply Voltages Diagnostic Modes . .. WO Port Configurations .. Isolating a Defective AC Stage. AC Signal Tracing .. Truth Table for U804) and K2 Accessories. Options... TEEE-488 Interface PCA... |. Tue RMS AC PCA...List of Illustrations External Dimensions... Line Voltage Selection Settings ... Adjusting the Handle Rack-Mount Kits. Installing the Si Front Panel Features. . Rear Panel Features Typical Error Message . Overrange Indication... ... Measuring Voltage and Resistance Remote Operation Block Diagram 33. Typical Command String 3-4. Commands Which Correspond to the Front Panel. 35. Device-Dependent Command Set . 3-6. Output Data Format ‘37. Trigger Selection Logic Diagram . 3-8. Interpretation of Messages . : Taking Readings with Local Control... Porras 323 . Example Program: Using the Serial Poll Register.......... : . Example Program: Record Enrors During Selftest Example Programs: Using the IBM PC ...... Gireuit Loading Error Calculation. Measuring Input Bias Current Error. 2-Wire Ohms Measurement 4-Wire Ohms Measurement Burden Voltage Enror Calculation. Waveform Comparison Chant . ‘Typical Crest Factors for Various Waveforms 749 Combined AC and DC Measurement 49 Reduction of Zero-Input Error 4-10 Overall Functional Block Diagram 1 52 DC Scaling (VDC and mA DC) . 53 ‘Track/Hold Amplifier ...... ‘Track/Hold Circuit Configurations Timing Diagram for One A/D Cyel Precision Voltage Reference . ‘Ohms Current Source. ‘Ohms Scaling ... 5-10 villList of Illustrations FIGURE 6-10. Gl. o12. 613. 6-14. GS. 6-16. 17. 6-18. 19. 6-20. 621. ‘805-1. Installing Option -05. 809-1: Installing Option -09. Analog-to-Digital Converter . First Remainder-Store Period. |. Autozero Period. Vacuum Fluorescent Display Digital Controller Block Diagram Read/Write Timing Diagrams for Internal Bus. Guard Crossing Circui 5. IEEE-488 Interface Block Diagram. 7. True RMS AC Option Block Diagram . True RMS AC+o-DC Converter... Connections for Kelvin-Varley Voltage First A/D Calibration Prompt ..... Calibration Functions . Optimizing Use of the S4S0A. Example A/D Calibration Program .. 8840A. Disassembly... Front Panel Disassembly... Removing the Display Window . U202 Pin Diagram oe Waveforms for In-Guard Troubleshooting Mode Waveforms for Display Logic. . ‘Typical Dynamic Control Signals... ‘Typical Output Waveforms for Track/Hold Circuit (TP103) Output of A/D Amplifier (TP101) . Waveforms at U101-24 and U101-25 ‘Typical Bus Data Line Waveform . : Waveforms at TP102 for Several Inputs on 2V DV Range. Calculating the A/D Reading From TP102 Waveform Option -05 Service Position. Option -09 Service Position. Guard Crossing Test Waveforms8840A Digital MultimeterSection 1 Introduction and Specifications 4-1. INTRODUCTION ‘This manual provides complete operating instructions and service information for the 8840A. If you want to get started using your 8840A right away, proceed to the ‘operating instructions in Section 2. If you intend to use the 8840A. with the IEEE-488 Interface (Option -05), read Sections 2 and 3. 4-2. THE 8840A DIGITAL MULTIMETER The Fluke 8840A Digital Multimeter is a high- performance 5-1/2 digit instrument designed for general- purpose bench or systems applications. Features of the 8840A include: + Highly legible vacuum fluorescent display + Intuitively easy front pane! operation * Basie de accuracy of 0.005% for 1 year + 2ewire and 4-wire resistance measurement + DC current measurement + Up to 100 readings per second + Closed-case calibration (no internal adjustments) + Builtein self-ests 1-3. OPTIONS AND ACCESSORIES ‘A number of options and accessories are available for the 8840A which can be easily installed at any time. The options include: + IBEE-488 Interface (Option -05), featuring: Full: programmability Simple and predictable command set Fast measurement throughput External Trigger input connector Sample Complete output connector ‘Automated calibration Low cost + True RMS AC (Option -09), featuring: * AC voltage measurement * AC current measurement Accessories include a variety of rack mounting kits, Probes, test leads, and cables. Full information about options and accessories can be found in Section 8, 1-4. SPECIFICATIONS Specifications for the 8840A are given in Table 1-1. External dimensions are shown in Figure 1-1. 4Introduction and Specifications es Teble 14. Speceatins DC VOLTAGE Input Characteristics. RESOLUTION FULL SCALE INPUT ance paors | sapiens RESISTANCE om 728008 mv 1 poo wa 7 {ator om Soar we 20v 19.9999V_ 100 wv 210,000 MQ. a ed "av ‘ona soy recon” mv foun “apap a tale retng ‘Accuracy NORMAL (S) READING RATE ........... 2(% of Reading + Number of Counts).> RANGE (24 HOUR 231°C" 90 DAY 235°C 1 YEAR 2325°C ome oom +> omar ome +6 av 0.002 +2 0.004 +3 0.005 +3 20v 0.002 + 2 0.005 +3 0.006 +3 200V 0.002 + 2 0.005 + 3 0.006 +3 stv ome +2 oes toms * Relative to calibration standards. * Using Offset control. When in fast reading rate with internal trigger and transmitting data out of the IEEE-488 interface, the 8840A display must be blanked (command D1) to ensure stated accuracy. “When offset control is not used, the number of counts are 5,7, and 9 for 24 hour, 90 day, and 1 year respectively. MEDIUM AND FAST RATES: In medium rate, add2 countsto number of counts. Infastrate, use counts for the number of counts. 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. + TO00V de or peak ac on any range. MAXIMUM INPUT NOISE REJECTION . ‘Automatically optimized at power-up for 50, 60, or 400 Hz. READINGS/ PEAK NM RATE SECOND" FILTER NMR? SIGNAL cMRR® 8 25 Analog & >98 dB 20V or >140 6B Digital 2x FS* M 20 Digital 5 dB 1x FS >100 dB F 100 None - 1x FS >60 dB * Reading rate with internal trigger and 60 Hz power line frequency. See “Reading Rates” for more detail. # Normal Mode Rejection Rati inM rate. 2.Common Mode Rejection Ratio at 50 or 60 Hz +0.1%, with 1 kA in series with either lead. The CMRR is >1400dB atde for all reading rates. +20 volts or 2 times Full Scale whichever is greater, not to exceed 1000V. ‘at 50 oF 60 Hz 0.1%. The NMRR for 400 Hz 0.1% is 85 dB in S rate and 35 dBIntroduction and Specifications 'SPECFICATIONS Table 1-1. Specifications (cont) TRUE RMS AC VOLTAGE (OPTION -09) Input Characteristics RESOLUTION FULL SCALE INPUT RANGE 5% DIGITS 5% DIGITS 4% DIGITS" IMPEDANCE 200 mv 199.999 mv Ww 10 1MQ av 1.99988 10. 100 ww shunted 20v 19.999 100 wv mv by 200v 199.998 1mv 10 mv <100 pF ov 700.00 10 mv 4100 mv "4% digits at the fastest reading rate. ‘Accuracy NORMAL (S) READING RATE + £106 of Reading + Number of Counts}? For sinewave inputs 310,000 counts’. FREQUENCY (H2) 24 HOURS? 231°C 90 DAY 235°C 1 YEAR 2325°C 20-45 1.2 +100 1.2 +100 12 +100 45-100 03 +100 0.35 +100 04 +100 100-20 0.07 + 100 0.14 + 100 0.16 + 100 20k-50k 0.15 +120 019+ 150 0.21 + 200 ‘50k-100k 0.4 +300 05 +300 05 +400 * For sinewave inputs betwoen 1,000 and 10,000 counts, add to Number of Counts 100 counts for frequencies 20Hzto 20 kHz, 200 counts for 20 kHz to 50 kHz, and 500 counts for 50 kHz to 100 kHz. # Relative to calibration standards. *When in fast reading rate with internal trigger and transmiting data out of the IEEE-488 interface, the 88408 cisplay must be blanked (command D1) fo ensure stated accuracy, MEDIUM AND FAST READING RATES ... In medium rate, add 50 counts to number of counts In fast rate the specifications apply for sinewave inputs >1000 counts and >100 Hz, NONSINUSOIDAL INPUTS ...... + For nonsinusoidal inputs 210,000 counts with frequency ‘components <100 kHz, add the following % of reading to the accuracy specifications, FUNDAMENTAL CREST FACTOR eed 1.0TO 1.5 15TO 20 2.0TO 3.0 45 Hz to 20 kHz 0.05 015 ae 20 Hz to 45 Hz and 20 kHz to 50 kHz oa or 15 Operating Characteristics MAXIMUM INPUT s+sseee+ 7OOV Ems, 1000V peak or2x 10" Volts-Hertz product (whicheveris less) for any range. 13introduction and Specifications SPECIFICATIONS ‘Table 1-1. Specifications (con!) ‘TEMPERATURE COEFFICIENT. :4(% of Reading + Number of Counts) per °C, 0°C to 18°C and 28°C to 50°C. FOR FREQUENCY IN HERTZ wNPUTS 20-20K 20K-50K 50K - 100K 210,000 counts 0.01949 0.02149 0.027 + 10 21,000 counts 0.019 +12 0.021 + 15 0.087 +21 COMMON MODE REJECTION ‘CURRENT >60 dB at 50 or 60 Hz with 1 k® in either lead. Input Characteristic RANGE FULL SCALE RESOLUTION 5% DIGITS 5% DIGITS 4 DieIrs 2000 mA 1999.99 mA 10 HA 100 WA "4%. digits at the fastest reading rate. Dc Current Accuracy NORMAL (S) READING RATE. 41% of Reading + Number of Counts). 90 DAYS 23 + 5°C 1 YEAR 23 + 5°C sta 0.08 +4 0.05 +4 >A 144 144 MEDIUM AND FAST READING RATES..Jn medium reading rate, add 2 counts to number of ‘counts. In fast reading rate, use 2 counts for number of ‘counts. * When in fast reading rate with internal trigger and transmiting data out of the IEEE-488 interface, the 8840A display must be blanked (command D1) ot ensure stated accuracy. ‘AC Current Accuracy (Option -08) NORMAL (S) READING RATE .~4(% of Reading + Number of Counts).' 1 Year, 28 + 5°C, for sinewave inputs >10,000 counts. FREQUENCY IN HERTZ 20-45 45-100 100- 5K" 2.0 + 200" (0.5 +200 0.4 + 200" * Typically 20 kHz ** Add 100 counts for sinewave inputs between 1000 and 10,000 counts. When in fast reading rate with internal rigger and transmiting data out of the IEEE-488 interface, the 8840A display must be blanked (command D1) to ensure stated accuracy. 14Introduction and Specifications ‘SPECIFICATIONS. Table 1-1. Specifications (cont) MEDIUM AND FAST READING RATES ... In medium rate, add 50 counts to number of counts. In fast ‘reading rate, tor sinewave inputs 1000 counts and frequencies >100 Hz, the accuracy is + (0.4% of reading + 30 counts). NONSINUSOIDAL INPUTS For nonsinusoidal inputs >10,000 counts with frequency ‘components <100 kHz, add the following % of reading to the accuracy specifications. FUNDAMENTAL CREST FACTOR FREQUENCY TOOTS TSTO20 20TOSO 45 Hz to 5 kHz 0.05 0.15 08 20 Hz to 45 Hz 02 o7 18 Operating Characteristics ‘TEMPERATURE COEFFICIENT Less than 0.1 x accuracy specification per *C from 0°C to 18°C and 28°C to 50°C. 2A de or rms ac. Protected with 2A, 250V fuse accessible at front panel, and internal 3A, 600V fuse. MAXIMUM INPUT BURDEN VOLTAGE V de or rms ac typical at full scale. RESISTANCE Input Characteristics RESOLUTION RANGE FULL SCALE CURRENT 5% DIGITS 5% DIGITS 4% DIGITS" | THROUGH UNKNOWN 2000, 199.9900. 1ma 10ma 1mA 2ko 1.99999 kO 10ma 100 ma 1mA 20k 19.9999 kQ 100 ma 19 100 vA 200 kA 199.999 ka 19 102 10 yA 2000 ka 1999.99 ka 100 1000 Sua 20Ma 19.9999 MQ 1000 1ko 0.5 yA “4% digits at the fastest reading rate. ‘Accuracy NORMAL (8) READING RATE ........... +(% of Reading + Number of Counts)" RANGE 24 HOUR 231°C? 90 DAY 235°C 1 YEAR 235°C 2000" 0.004 +3° 0.011 + 4 0.014 + 4° 2402 0.0028 + 2 001 +3 0.013 +3 20Ka 0.0028 +2 O01 +3 0013 +3 200 ka 0.0028 + 2 O01 +3 0013 +3 2000 ka 0.023 +3 0.027 +3, 0.028 +3 20MQ 0.023 +3 0.043 +4 0.044 +4 ‘Within one hour of zero, using offset control, Relative to calibration standard. 2 Applies to 4-wire ohms only. “When in fast reading rate with intemal trigger and transmitting data out of the IEEE-488 interface, the 6840A 200,000 counts) +9,999996+49,>VDC Overrange (= 200,000 counts) +1.00326+21 Error message INSTRUMENT ‘annn [CR] [LF] [EON CONFIGURATION DATA (From GO, G4, G5, EXAMPLE: G6, and G7) 1100 Default GO value ‘SRQ MASK DATA fan [CR] {LF} [E01] (From G1) EXAMPLE: 32. SRQ on any error USER-DEFINED MESSAGE ‘aaaaazaaaaaaazaa [CR] {LF} (EO!) (From G3) EXAMPLE: FLBB40A.01-25-84 Hino messages have ever been stored, a string of 16 nulls (Hex 00) will be returned. INSTRUMENT — FLUKE, mmmmm, 0, Vain {CR} [LF] [EON FLUKE @840A with IEEE 488 IDENTIFICATION interface software version (From G8) EXAMPLE: FLUKE, 88404, 0, V4.0 © Numeric data is always in volts, amps, or ohms. © The terminators CR, LF, and EOI are selected with the Terminator Commands (Wn). ‘© The sutfix, defined below, is enabled with the Y1 command and disabled with the YO command. (Default = YO.) SUFFIX FORMAT a >| voc vac OHM IDC lac Function Indicator > Reading is overrange (> 200,000 counts) _Reading is not overrange but can be over voltage (© 1000 Vdc or 700 Vac) Leading Comma (Always present in suffix). Most versions of BASIC expect ‘multiple input values to be separated by commas. ie., input @ |, N, S$to acquire the numeric portion and suffix string. Figure 3-6. Output Data FormatRemote Programming DDEVICE-DEPENDENT COMMAND SET 3-18. G3 (Get User-Defined Message) ‘The G3 command Joads the output buffer with the user- defined message stored in calibration memory during the calibration procedure. The message consists of 16 ASCIL characters, as shown in Figure 3-6. ‘The message is stored in calibration memory during cali- bration using the P3 command. If fewer than 16 characters have been stored, the remaining characters returned are spaces. If no message has ever been stored, a string of 16 null characters (hex 00) will be returned. Some example output strings follow. Example FL8840A.12-17-83 CR LF Meaning Identifies instrument and gives cal date, Gives cal date. The last eight characters are blank. 3-16. G4 (Get Calibration Status) ‘The G4 command is used when calibrating the 88404 under remote control. The command loads the output buffer with the instrument's calibration status in the format shown in Figure 3-6. The status is represented by a four-digit integer which is interpreted in Table 3-1. 01-25-84 = CRLF ‘The first two digits are always 1 and 0. The third digit indicates whether or not the calibration verification mode is enabled. (This mode is enabled only when the calibra- tion mode is enabled.) The fourth digit indicates whether (or not the calibration mode is enabled, and if so, which part of the calibration procedure the 8840A is in. Example output strings follow. Example Meaning 1000 CRLF 1: Leading 1 0: Leading 0 0: Not in cal verification 0: Cal mode disabled 1001 CR LF 1: Leading 1 0: Leading 0 0: Not in cal verification 1: Cal mode enabled; A/D cal selected 3-17. G5 (Get IAB Status) ‘The’ GS 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 (au- torange on or off), and the OFFSET feature (OFFSET on or off). The first digit is always 1. An example output string follows. Example Meaning 3011 CRLF 1: Leading 1 0: FRONT inputs 1: Autorange off 1: OFFSET feature on It is useful to know whether autorange is on or off because this information is not available from the GO command. For example, the GO command could indicate that the 8840A was in the 200 mV range, but it would not indicate whether the 8840A was in autorange or manual range. 3-18. G6 (Get YW Status) ‘The G6 command Joads the output buffer with the YW status in the format shown in Figure 3-6. The YW status is four-character string which indicates which terminators aie selected and whether the output suffix is enabled or disabled, as shown in Table 3-1. The first two digits are always 1 and 0. An example output string follows. Example Meaning 1015 LF CR 1: Leading 1 0: Leading 0 1: YI (enable output suffix) 5: WS (enable LF only) 3-19, G7 (Get Error Status) ‘The G7 command copies the error status register into the ‘output buffer in the format shown in Figure 3-6. The first two digits are always 1 and 0. The second two digits Tepresent the appropriate error code, if an error has occurred. (Error codes ate listed in Table 2-1, Section 2). If an error has not occurred, the second two digits are 00. ‘An example output string follows. Example ‘Meaning 1071 CRLF 1: Leading 1 0: Leading 0 71: Syntax error in device-dependent ‘command string ‘The G7 command gives the error status as it exists when the command is executed at its position in the input string. ‘The G7 command does not clear the error status register. For more information about error messages, see paragraph 3-40. 3-20. G8 (Get Instrument Identification) ‘The G8 command copies the 8840A instrument identifice- tion 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 indi- cates the instrument model number, the third is always 39Remote Programmir SECC DEPENDENT COMNARD SET zero, and the fourth indicates the version number of the IEEE-488 interface software. Example Explanation FLUKE8840A,0,V4.0 CF This instrument is a Fluke LF ‘8840A with IEEE-488 inter- face software version 4.0 ‘9-21. N (Numeric Entry Command) Format Explanation Nemumeric entry> Where is one of the following: < «signed real number>Ecsigned cexponent> Example Explanation “N1201" Enters the five-digit imeger 12001 “N-1.23E2” Enters -1.23 x 10? “N+15433E-1" Enters 15433 x 10! ‘The N command enters mumeric values for use with subse~ quent Put commands. The interpretation of the numeric value depends on which Put command it is used with. ‘The E can be used within an N command for entering an exponent of 10. The N can be used without an E, but an E requires a prior N. The exponent can be any integer from 9 to 49. ‘The mantissa may exceed 5-1/2 digits. The 840A accurately calculates the appropriate exponent and then isregards all but the first 5-1/2 digits of the mantissa. However, a syntax error will occur if the numeric entry overflows the input buffer. Example Explanation “N123456789" Enters +1.23456 x 10% 3-22, Put Commands ‘The Put commands PO through P3 set up the 8840A’s ‘configuration and operating modes by entering (“putting”) ‘information in the appropriate registers. The put com- mands are described further in the following paragraphs. 9-23. PO (Put instrument Configuration) Format Explanation Nefrst>PO Where is a four-digit integer interpreted as arguments for the F, R, S, and T commands. Example Explanation 340 “N3120 PO” Identical to F3 R1 S2 TO. Selects 2 WIRE k@ function, 2002 range, fast sample rate, continuous trigger. ‘The PO command allows broadside loading of the Func- tion, Range, Reading Rate, and Trigger Mode commands (FR, and 7). The codes for these commands are listed in Figure 3-5. ‘A mumeric entry for PO must be within +1000 and +6724. Each of the four digits must not exceed its maximum allowed value (6, 7, 2, and 4, respectively) or an error ‘message will occur and the instrument configuration will remain unchanged. The entry may be expressed 9s an integer, real number, or real number with exponent, as described under the N command. Any fractional part is ignored. Example N3112 PO” Explanation Sets the 8840A to F3, R1, Si, and T2. 3-24. P1 (Put SRO Mask) Format Explanation N«SRQ mask>P1 Where SRQ mask is a two-digit integer from 00 to 63. ‘The P1 command is used to program the 8840A to make service requests on user-specified conditions. The two- digit code for the SRQ mask is interpreted in Table 3-1 under the G1 command. For more about the SRQ mask, ‘see paragraph 3-47. Numeric eatries for the P1 command must be between 0 ‘and +63 (inclusive), or an errar will occur and the SRQ mask will remain unchanged. The entry may be expressed as an imteger, real umber, or real number with exponent, as described under the N command. Any fractional partis ignored. Example Explanation “NO.I7E+2 PI" Sets SRQ mask to 17. Enables SRQ ‘on data available or overrange. “NI PI" Sets SRQ mask to O1. (A leading zero is assumed.) Enables SRQ on over- range. 3-25, P2 (Put Calibration Value) Format Explanation Nevalue>P2 ‘Where can be an integer, real ‘number, of real number with ¢xpo- nent, aS described under the N com- ‘mand. Example Explanation “NI P2” If the 8840A is in VDC, the|next calibration input expected is 1.00000 de. ‘The P2 command is used to enter variable input calibration ‘values just like the front panel VAR IN button. To acceptRemote Program DEVICE DEPENDENT COMMAND S: Table 3-1. Status Data ‘OUTPUT COMMAND ae MEANING 1 = 6 a8 in Function commands (Fn) 9 for Selt-Test 1 = 6 as in Range commands (Fin) 0 - 2 as in Reading Rate commands (Sr) © - 4 as in Trigger Mode commands (Th) @ mn an = Note: SRQ mask vaiues may be added for combinations. Example: $3 for SRO on overrange or any error. 00 for SRQ disabled (default) 01 for SRQ on overrange (04 for SRQ on front panel SRO 08 for SRQ on cal step complete 16 for SRO on data available ‘82 for SRQ on any error gs ‘aaaaaaaaasaaaaaa 16 user-defined ASCII characters Ge 10m v ‘Not in cal verification 1 Cal vertication © Not in calibration mode 1 AD calibration 2 Offset and gain calibration 4 HF AC calibration es tiab i 0 FRONT inputs selected 1 REAR inputs selected © Autorange on 1 Autorange off (Manual range) 0 OFFSET off 1 OFFSET on es 1Oyw y= we 0 output suffic disabled 1 output suffix enabled 0 - 7 a8 in Terminator commands (Wn) or 0nn/ ‘nn represents error code (See Table 2-1) ey FLUKE, mmmmm, mmmmm = 8840A OVn.n Van = IBEE-488 Interface sofware version number the P2 command, the 8840A must be in the calibration ‘mode (enabled by pressing the front panel CAL ENABLE ‘switch). Otherwise, the P2 command will generate an error message. ‘The variable input is a measurement value that is to be used as the calibration value for the next calibration step, Its format is the same as a measurement value. But since it is coming from the controller, the value can be specified using any valid format (signed integer, real number, or real number with exponent). For example, if the 8840A ‘prompts for an input value of 100 for the next calibration step, but the available source is 98.97, the variable input can be specified as “N+9.897E+1”, “NO.9897E2”, “N9SITE-2”, etc. All of these strings result in the same oatRemote ramming DEVICE DEPENt ‘COMMAND SET value being used for the next calibration step. For com- plete 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.8840.12-1783" Loads the message “FL.8840.12-17-83" into cali- bration memory. “P3HIMOM” Loads the message “HIMOM” into calibration memory. The remaining eleven characters are assumed 10 be blank ‘The P3 command stores a user-defined message in the internal calibration memory during remote calibration. The ‘message may be read with a subsequent G3 command. ‘The message may consist of up to 16 ASCII characters, ‘and typically represents the instrument's identification, calibration date, calibration facility, etc. If fewer than 16 characters are specified, spaces are appended to fill the Message to 16 characters. Spaces and commas in the 16-character input string are suppressed. Lower-case letters ate converted to upper-case. NOTE If fewer than 16 characters are specified, the P3 command must not be followed by other commands in the same input command string. Otherwise, the subsequent commands will be misinterpreted as part of the 16-character string. To accept the P3 command, the 8840A must be in the calibration mode (enabled by pressing the front panel CAL ENABLE switch). Otherwise, the P3 command will gener- ate an error message. 3-27. Rn (Range Commands) ‘The Range commands duplicate the front panel range buttons. For example, RO selects autorange, and Ré selects the 200V/200 k@ range. ‘The R7 command turns autorange off, just as the AUTO ‘button does when it is toggled. Command R7 puts the 8840A into manual range, selecting whatever range the instrument is in when the command is received. ‘The 8840A defaults to RO on power-up and any device- clear command (*, DCL, or SDC). The range setting can be read using the GO command. B12 3-28. Sn (Reading Rate Commands) ‘The Reading Rate commands duplicate the front panel RATE button. Like the RATE button, the reading rate ‘command also selects the mumber of digits displayed and the filter setting. (Filter settings are shown in the specifications in Section 1) ‘The 8840A defaults 10 SO on power-up and any device- clear command (*, DCL, or SDC). The reading rate can be ead using the GO command. 3-29. Tn (Trigger Mode Commands) ‘The Trigger Mode commands duplicate the front pane] 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 pane! trigger, and two bus triggers. Note that the front panel ‘TRIG button is enabled only while the instrument is under local control In the continuous trigger mode (TO), triggers are initiated at the selected reading rate. Each new reading is loaded {nto the output buffer as it becomes available, unless the instrument is busy sending previous output data. ‘The trigger mode can be read using the GO command, The 8840A defaults to TO on both power-up and any device- clear command (*, DCL, or SDC). 3-30. Wn (Terminator Commands) ‘The Terminator commands select what terminators the ‘840A appends to every output string. The available termi- ‘nators are: Return (CR), Line Feed (LF), and End Or Identify (EON). R and LF are ASCII control codes, sent over the data lines just like output data. EOI is a uniline message which {s sent simultaneously with the last character in the output string. Normally, each output string is terminated with CR followed by LF’ and EOI. ‘The terminator selection can be read using the G6 com- mand. The 8840A defaults to 'WO on power-up and any device-clear command. 3-31. XO (Clear Error Register Command) ‘The XO command clears the 8840A’s error status register. After an XO command is executed, a G7 command (Get, Error Status) would return 1000 (a0 errors). Note that the error status register is also cleared when any device-ciear command (*, DCL, or SDC) is executed. However, X0 is useful for clearing the error status register without forcing a complete instrument clear (as d0 the device-clear commands). 3-32. Yn (Suffix Commands) ‘The Suffix commands enable or disable a suffix which the ‘840A can append to all numeric data (the data inRemote Programmi: Device CEPENOENT COMMAND SE ‘TRIGGER METHOD CONTINUOUS TRIGGER BUS TRIGGER (? or GET) REMOTE FRONT PANEL, ‘TRIGGER REAR PANEL ‘TRIGGER 71,73 DEVICE CLEAR, | EX TRIG BUTTON ‘© Switches represent effect of indicated commands, buttons, and remote/local status. © Instrument shown in power-up state (TO, local, rear panel trigger enabled). DEVICE CLEAR TOGGLED BY MEASUREM CIRCUITRY 4 *With EXTRIG enabled. ‘TRIGGER METHOD DESCRIPTION 1. Continuous Trigger 2.2 Command 3. GET Command controller. 4. Front Panel Trigger 5, Rear Panel Trigger Continuous trigger generated by 8840A in internal trigger mode (TO). ‘Single trigger initiated by ? command from controller. Single trigger initiated by GET command (an interface message) from Single trigger initiated by front panel TRIG button. ‘Single trigger initiated from rear panel EXTTRIG input. (Disabled by TO, T2, T4,) Figure 3-7. Trigger Selection Logic Diagram esponse to G2 or trigger commands). The suffix includes @ comma, an overrange indicator (>), and a function indicator (VDC, VAC, OHM, IDC, ot IAC). The suffix is illustrated in Figure 3-6. An example of suffixed data is given in paragraph 3-43. To read suffixed data with a controller using BASIC, one can read the whole line into a string variable and then ‘convert the numeric part imto a mumeric variable. However, it is much easier to read the numeric part directly into a ‘numeric variable and the suffix into a string variable. The leading comma of the suffix serves as a convenient delimiter. For example, a BASIC program statement might be: pur 1A, Bg 313Remote Programming DEVICE DEPENDENT COMMAND SET ‘The suffix status can be read using the G6 command. The 840A defaults to YO on power-up and any device-clear command (*, DCL or SDC), unless in talk-only mode. 3-83. ZO (elf-Test Command) ‘The ZO command initiates the diagnostic self-tests as does pressing the front panel SRQ button for 3 seconds. The ‘8840A then runs through the tests in sequence. (For a description of the self-tests, see the Maintenance section.) If the 8840A detects an error, an error message is loaded into the output buffer and displayed on the front panel. Afier the last test, the 840A is reset to the power-up configuration, and it begins taking readings. It is an error to send the 8840A device-dependent com mands during the selfests. However, the controller can sill make the 840A a talker to read the output buffer uring the test, and thus record each error that occurs, ‘except that only the last of the digital selftest errors can be read. After the tests, only the last error is stored in the ‘output buffer if more than one error occurred. Error messages are indicated by an exponent of +21. For ‘more about error messages, see paragraph 3-40. Since the 8840A is reset at the end of the self-tests, the ZO ‘command should be the last command in a given com- mand string. The 8840A will ignore any subsequent com- ‘mands in the same command string. ‘When the selftests are complete and no errors have ‘occurred, the serial poll register will have bit 5 (Data Available) true and bit 6 (Any Error) false. See paragraph 3-50 for more about the serial poli register. 3-34. * (Device-Clear Command) ‘The asterisk command (*) is a device-dependent message which resets the 8840A to the power-up default settings and clears all registers and buffers except for the input buffer. The remote/local status remains unchanged. The asterisk command performs the following: 1. Implements the default settings F1, RO, $0, TO, DO, BO, YO, WO. 2. Clears the error status register (equivalent to XO). 3. Zeros the SRQ mask, prohibiting service requests (equivalent to NO P1). 4, Zeros the mimetic entry register (equivalent to NO). 5. Zeros the serial poll register. 6. Sets the SRO line false. ‘The asterisk command is executed in its proper turn in a string, just like any other command, without affecting the contents of the input buffer. All commands which precede the asterisk command are performed. ‘The asterisk command is useful to ensure that the 840A is initialized to the same state each time a program is run. By contrast, the similar interface messages DCL (Device Clear) and SDC (Selected Device Clear) cause the entire input buffer to be cleared immediately. DCL, SDC, and the asterisk command are all considered to be device-clear commands because the results are so a4 similar, however, DCL and SDC are not identical to the asterisk command described here. DCL and SDC) are discussed further in the paragraph on interface messages. 9-35. 2 (Single-Trigger Command) ‘The Single-Trigger command (?) causes the 8840A to take a reading and place the result into the output buffer, To ‘accept this command, the 8840A must be in extemal trigger mode (selected by the Tl, T2, T3, or T4 com- mand). ‘The Single-Trigger command is one of five ways to trigger a reading. (See Figure 3-7.) Of these, only the Single~ Trigger command (?) and’ the Group Execute Trigger ‘command (GET) are loaded into the input buffer. 9-96. INPUT SYNTAX The following paragraphs describe how 10 construct groups of commands for the 8840A. A few definitions are resented first, followed by @ description of how the 8840A processes input commands. Guidelines are then summarized in four syntax rules. 3-37. Definitions + Output commands: Commands which load data into the output buffer. The output commands are: the Get ‘commands (GO through G8); the Single-Trigger Com- ‘mand (?); the Continous Trigger command (TO); 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 8840A to execute all device- dependent commands since the previous terminator. Terminators are CR (( Reurn), LF (Line Feed), EO! (End Or Identify), and GET (Group Exe- cute Trigger). ‘+ Input command string: One or more device-dependent ‘commands followed by a terminator. 3-38. Input Processing ‘When the 8840A receives commands from the bus, it stores them in a 31-character input buffer as a continuous string of characters. Commands in the input buffer are not executed or checked for syntax until an input terminator is received or the input buffer becomes full. The only valid input terminators are CR, LF, GET (Group Execute Trigger), and/or EOI. ‘When the 8840A receives an input terminator, it executes the previous commands in the order in which they were received. As input characters are processed and executed, space is made available in the input buffer for new charac- ters. Ifthe input buffer becomes full, the 8840A stops accepting characters from the bus until all complete command strings curently in the input buffer have been executed. In this way, characters sent to the 8840 are never lost due 10 buffer overflow.Remote Programmir neu Sv In some instances, a terminator is automatically transmit- ted at the end of the controller's output string. For exam- ple, in Fluke BASIC, the PRINT statement always finishes with a CR LF pair. If a controller does not have this feature, the programmer must transmit a terminator explic- itly. ‘The 8840A accepts alphabetic characters in either upper or lower case. Spaces, commas, and control codes are ignored ‘and are not placed in the input buffer. If the 88404 receives a group of terminators (such as CR LF or CR LP EOI), only a single terminator is loaded into the input buffer. Numeric values used in PUT commands may be in NR1, NR2, or NR3 format as described in the IEEE-488 Codes and Formats Recommended Practice. (These corres pond to the signed integer, real number, and real-number- with-exponent formats described under ‘the N command.) For reference, Figure 3-8 shows how the 8840A interprets messages. legal commands (e.g., F9) generate an error message, but are otherwise ignored, and do not affect the instrument's configuration. Example “By Explanation ‘This would load the output buffer with an error message and select F1 (established by the * command). 9-99. Syntax Rules Four syntax rules should be followed when constructing input command strings. They are: + RULE 1: Read output data only once. To prevent old (previously read) data from being read ‘a second time by mistake, the output buffer is always cleared after it has been read. If the output buffer is ead twice without an intervening output command, the 8840A will not respond to the second attempt to read the output buffer. (However, if the 8840A is in ‘TO, no intervening command is necessary.) + RULE 2: Use no more than one output command per input command string. Because the 8840A has only one output buffer, it writes new data over old. If an input command string contains more than one output command, only the data from the last command can be read. Example Explanation “F1T3 2F2 2” Improper construction. The second iwigger writes over the first. To obtain two readings, send two complete command strings (sepa- rated by terminators). “F2 R3 $0 T3 Correct construction. The string r contains only one output com- mand “F2 R3S0” Comect construction. It is permissi- ble for a string not to contain an ‘output command. + RULE 3: Read the output data generated by one input command string before sending the next input com- mand string. Output data remains available in the output buffer until it is ead, or until the next input command string is received. AS soon as the controller finishes reading the output buffer, or as soon as the 8840A receives a new input terminator, the Data Available bit in the serial poll register is set false. When this bit is false, data can no longer be read from the output buffer. ‘Therefore, an output string which is available must be ead by the controller before, rather than after, the next input command string is sent. Rule 3 is most evident in the extemal trigger mode, and is best demonstrated by a programming example, The following program is written first incorrectly, and then conectly, in Fluke BASIC using the 17224 Instrument Controller. Incorrect example: 100 PRINT €3, "32 200 PRiwn @3, "Fa" 300 INPUT @2, a Im this incorrect example, the INPUT statement is located incorrectly for reading the measurement data fom line 100. The new input command string “F4” disallows the reading of data from the output buffer. correct example: 300 PRINT @3, “71 77 200 INPUT @3, a 300 PRINT @3, “Pat Jn this example, the reading taken at line 100 is read at line 200. Then the F4 command is sent. Note that in the external trigger mode, the reading from line 100 flashes on the 8840A display 100 briefly to see. This is because the function change at line 300 blanks the display unt) the next trigger. ‘The previous example could also be correctly pro- grammed as follows: 300 PRINT @3, "Ti ? Fa" 200 INPUT €3, a + Rule 4: If an input command string contains a trigger, ‘enter the commands in the following order: @ Commands to configure the instrument (if any). b. The trigger command, Commands to re-configure the instrument (if any). 4. Terminator(s). ‘The principle behind this rule is that the 8840A executes all commands in the exact order they are received, from left to right as written. Example Explanation “F3 F4 7” Improper construction. F3 is effectively discarded. 345Remote Programming INPUT SYNTAX, DEVICE-DEPENDENT MESSAGES Single-character Commands of ‘Two-character Commands Bn Cn Dn Fn Gn Pr, Rn Sn Wn Xa Yn Zn Numeric-entry Characters NE.+—0123456789 Terminators cR uF GET EO! INTERFACE MESSAGES. Address Messages MLA MTA UNL, UNT Universal Commands ATN DeL FC LLo REN ‘SPD SPE Addressed Commands GET GTL soc Ignored Characters comma space All other ASCII non-printing characters (except CR and LF) ERROR-PRODUCING CHARACTERS "HSL S=>: @t/) Vw HIJKLMOQUV ‘These two commands are complete in them- selves (except for string terminator). Each of these commands requires the single numeric digit (n). ‘These characters are used for entering numbers. Carriage Return Line Feed Group Execute Trigger End Or Identity (used as END/DAB) My Listen Address My Talk Address Unlisten Untalk Attention Device Clear Interface Clear Local Lockout Remote Enable Serial Poll Disable Serial Poll Enable Group Execute Trigger Go To Local Selected Device Clear ‘These characters may be inserted anywhere in a character string without affecting the string. ‘They carry no special meaning and are ignored by the 8840A. They are not placed in the input butfer. The error annunciator is displayed on the ‘88404 front panel when one of these characters is encountered (ERROR 71). Figure 3-8. interpretation of MessagesRemote Programming INPUT SYNTAX, “F3.7F4” Correct construction. The’ 8840A is con- figured in F3, and the trigger is executed. ‘Then the 88404 is left in F4. ‘3-40. OUTPUT DATA ‘The following paragraphs describe the data that can be Toaded into the 8840A output buffer and sent to the IEEE-488 bus. The paragraphs describe how and when data is loaded into the output buffer, the types of output data, and their relative priority. Note that the 8840A can also send data to the IEEE-488 bus from the serial poll register. For a description of this data, see paragraph 3-50. 3-41. Loading Output Data The output buffer is loaded when the 8840A receives an output command, or when an error occurs. Output com~ mands are those device-dependent commands which load the output buffer with data: Get commands (GO through G8) Single-tigger command (?) Group execute tigger (GET) Continuous Trigger (TO) Because the 8840A 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 acmally loaded onto the TEEE-488 bus until the controller addresses the S840A as a talker. This is done by sending the interface message MTA (My Talk Address). 3-42. Types of Output Data The types of data that can be loaded into the output buffer are shown in Figure 3-6. Each type has its own format. Error messages, which are loaded into the output buffer if fan error occurs, are formatted as numeric data. 3-43. Numeric Data and Error Messages Numeric data is loaded into the output buffer in response ‘to the G2 command or an instrument trigger, and has the Table 3-2. Numeric format shown in Table 3-2. The exponent is always a ‘multiple of 3, as in engineering notation. The position of ‘the decimal point matches the front panel display. Numeric data is of constant length, It is 11 characters (plus terminators) when the suffix is disabled, and 16 characters (Plus terminators) when the suffix is enabled. ‘The suffix is enabled by the Y1 command, and consists of five ASCH characters as shown in Figure 3-6. The suffix is appended only to numeric data, never to status data. The terminators are determined by the Terminator commands. ‘The defeult is CR LF EOI. ‘There are three types of numeric data: measurement data, overrange indication, and error messages. ‘3-44. MEASUREMENT DATA ‘Measurement data has the numeric data format shown in Table 3-2, and is always in the units of volts, amps, ot ohms. NOTE In the fast (F) reading rate, the least signifi- ‘cant digit is always zero, and should be dis- regarded when interpreting accuracy specifications. ‘8-45. OVERRANGE INDICATION If a reading is overrange (2200,000 counts), the measure- ‘ment data has the following format: #9.99999E49 Overvoltage readings (> 1000V de or 700V ac) do not result in this display, 3-46. ERROR MESSAGES If the 8840A detects an error, it loads an error message into the output buffer in the following numeric format: +1.00mE+21 ‘The digits xx represent a two-digit error code. (Error codes are listed in Table 2-1, Section 2.) The suffix is always suppressed for error messages. Output Data Format RANGE MEASUREMENT DATA OVERRANGE ERROR voc, VAC 2, 4WIRE k2 | mA DC, mA AC INDICATION MESSAGES Ri =P 0KES Tro 0xE+0) - +29,999998+9 1.000621 R2 21.2000KE+0 212000063 - 29.99999E+9 1.000421 FS X200KE+0 21x 2000E+3, - 29.99999E+9 $4.000xE+21 Ra shoo0E+0 S10 200843 - 29,99999E+9 $4.00xE¥21 RS hoouxE+0 1000843 20x20 +29.99999E+9 +1.000E+21 Re - 21x06 - +=9.99999E+9 #1.00xE+21 347Remote Programming ‘OUTPUT DATA Example +10071E#21 CR LF Explanation ERROR 71: Syntax error in device-dependent command string. ‘As with local operation, none of the errors are latching. ‘except for ERROR 31. If the mA DC or mA AC function is requested while the FRONT/REAR switch is in the REAR position, ERROR 31 will persist until the switch is set to FRONT or another function is selected. To check for an error condition, test whether the output buffer data is greater than or equal to +1E+21, or test the Any Error bit (bit 6) in the serial poll register. 3-47. Status Data ‘Status data is the output in response to GO, G1, G3, G4, G5, G6, G7, and G8 commands. The data is formatted as shown in Figure 3-2, and is interpreted in Table 3-1. Examples of status data can be found in the description of, ‘the Get commands. The user-defined message loaded by the G3 command ‘consists of 16 characters plus terminators. The SRO mask Joaded by the G1 command consists of two integers plus terminators. All other status data except G8, is always a four-digit integer plus terminators. The terminators LF (Line Feed) and CR (Carriage Return) each add an extra character when enabled. ‘The 8840A begins some status data with a leading ASCII one (1) or a one and a zero (10). This prevents the ‘controller from suppressing any leading zeros present in the 8840A’s output string. It also gives a uniform four- character length to all instrument configuration data. ‘Status data from the Get commands reflects the status of the 8840A at the time the command is executed at its place in the input command string. 348. Output Priority Since only one output string is allowed per input command string, the 8840A gives priority to some types of data over others. An input command string may call for more than one output string. (For example, an input string may contain a Get command but also cause an error message.) However, the output buffer is loaded with only one output string. That string is selected according to the following Priority: 1. Status data (from GO, G1, G3, G4, GS, G6, G7, or G8) 2. Emor messages (if an error exists) 3. Numeric data (from G2 or a trigger) 318 ‘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 ‘mumeric data is requested. ‘349. SERVICE REQUESTS ‘Service requests let bus instruments get the attention of the system controller. The are sent over the SRQ line (one of the IEEE-488 bus lines). If more than one instru- ment on the bus is capable of sending service requests, the controller cari leam which one made the request by taking a serial poll. Each device (including the 8840A) responds ‘to the poll by sending the contents of its serial poll register. The serial poll register indicates whether or not the device requested service, and if so, the reason for the request. ‘The 840A may be programmed to make a service request on user-specified conditions. The conditions are specified by entering a value for the service request mask (SRQ mask) with the P1 command. The SRO mask works by ‘monitoring the serial poll register, which in turn monitors various conditions in the 8840A. Service requests may also be initiated using the front panel ‘SRQ button if it has been enabled by the SRO mask. 3-50. The Serial Poll Register ‘The serial poll register is a binary-encoded register which contains eight bits, as illustrated in Figure 3-9. The con- twoller can read the 840A serial poll register at any time by taking a serial poll. Because serial poll register data is loaded directly onto the bus (instead of being loaded into ‘the output buffer first), reading the serial poll register leaves data in the output buffer intact. ‘The eight bits of the serial poll register are described in Figure 3-9. Note that the SRO mask uses bits 1 through 6 to set bit 7 (the ROS bit). When the ROS bit is set true, ‘the 8840A. sets the SRQ line true, which generates a service request. A bit is considered true when itis set to 1. + Bit 1 (the lowest-order bit) is set true on overrange. When ove ‘occurs, the output buffer is loaded +29,99999E+9 (and a suffix, if enabled). + Bit 2 is not used. It is always set to 0. + Bit 3 is set true when the front panel SRQ button is pressed. + Bit 4, Cal Step Complete, is set true when a store ‘command is completed in the calibration procedure. + Bit 5, Data Available, is set te every time the output buffer is loaded, regardless of the kind of output data (including error messages). This bit is cleared (set to ©} when any new bus input occurs, when the output buffer is read, or when an external trigger occurs. + Bit 6, Any Enror, is set true whenever an error condi- tion occurs. At the same time that bit 6 is set true, the ‘output buffer is loaded with an error message.Remote Pi SERVICE interface messages described here originate at the con- troller. 3-53. Address Messages ‘Address messages are used by the controller to communi- cate talk and listen control to other devices on the bus. ‘Address messages are sent over the eight data lines of the bus while the controller holds ATN true. Address mes- sages are processed immediately and are not placed in the input buffer. The address messages are: + MLA My Listen Address — Addresses a device to listen + MTA My Talk Address -- Addresses a device to talk * UNL Unlisten - Addresses all listeners to unlisten + UNT Untalk — Addresses all talkers to untalk 3-54, Universal Commands Universal commands are accepted and interpreted by all devices on the bus. The commands are of two types, ‘multiline messages and uniline messages. Multiline mes- sages are sent over the eight parallel data lines in the IEEE-488 bus. Uniline messages are sent over one of the individual interface management lines in the IEEE-488 bus. All universal commands except DCL are processed immediately by the 8840, ahead of any device-dependent commands. Only DCL enters the 8840A input buffer. ‘The 8840A responds to the following universal messages: ATN Attention ~- A uniline message which causes the 8840A to interpret multiline messages as interface messages (AD, AC, or UC). When false, multiline messages are interpreted as device-dependent messages. IFC Interface Clear -- A uniline message which clears only the interface (not the 8840A) by placing it in a known quiescent state. REN Remote Enable ~ A uniline message which, when received with MLA, switches the 88404. to remote. When REN is set false, the 88404. ‘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. DCL performs the ‘same operation as the device-dependent com- mand *, except that it is read before any other characters that are already present in the input buffer, and cleats the entire input buffer. Pro- ‘cessing then continues normally. The action of DCL is not immediate; if the 8840A is taking a reading when DCL is received, the DCL ‘command is executed after the measurement is finished. LLO Local Lockout ~ A multiline message which disables the front panel LOCAL button. The result is that the local mode is not accessible by front panel control. SPD Serial Poll Disable ~ A multiline message which removes the serial poll enable state. SPE Serial Poll Enable — A multiline message ‘which causes the serial poll data (rather than ‘output buffer data) to be transferred on the bus ‘once ATN becomes false. 9-55. Addressed Commands ‘Addressed commands are multiline messages which are accepted and interpreted by only those devices currently addressed to listen. The 8840A responds to the following addressed commands: GET Group Execute Trigger ~ (Not to be confused with the device-dependent Get commands.) GET loads a trigger command imo the input buffer and also terminates the string at that point. Only a single character is loaded into the input buffer. The trigger command is executed in its proper tur in the input string, rather than immediately. When executed, GET initiates a measurement. GTL Go To Local ~ Causes the 840A to switch to local. This command does not enter the input buffer. Ifthe display has been blanked (with a D1 command), issue 2 DO command before sending GTL. SDC Selected Device Clear -- Identical 19 the tuniversal command DCL, but is accepted and interpreted by current listeners only. Therefore, it clears the 8840A only if it is addressed to listen, 3-56. TALK-ONLY MODE The talk-only mode lets you take advantage of the remote capability of the 8840A without having to use an instru- ment controller. To put the 8840A in the talk-only mode: 1. Tum the 8840A POWER switch OFF. 2. Set the rear panel TALK ONLY bit switch to 1 (the up position). 3. Connect the 8840A vie the IEEE-488 bus to your ‘Printer, data logger, or other device. Configure the other device as a listener only Turn the 840A POWER switch ON. Configure the 8840 with the front panel controls. The 8840A 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 power-up as long as you then send the 8840A the IFC command. 3-57. REMOTE CALIBRATION ‘The 8840A can be calibrated over the IEEE-488 bus using remote commands. Refer to the Maintenance section for details.Remote Programming raoesnay meee Table 3-3. Immediate-Mode Commands for Various Controllers FUNCTION penronuey | FLUKE-BASIC w-neLon | HP-BAsiC onnPesrere| TEBASIC onan orsrzan | Wroascaeutor | and HP.8S Callan | Graghes non INITIALIZE Po ww PORTO 7 CLEAR? wt CLEAR insiument | CLEAR gH cero CLEAR 08 Pai @a"e= REMOTE Commancs | REMOTE Os tem 708 REMOTE To8 warre ese. toca. Cone toca @« taroe toca 7s warre ee Serena TRIGGER | PRN gueTi” wa 704-71" oureut «rr | pant gent TRIGGER smart | TIC ee wore TRIGGER 708 main 6 Getouimt bate | INPUT @MA reso A ENTER rota wowe2) | weuT @eA paint oetetoseeen | printa mA pan A@ice) | PANT A CONFIGURE tr VA0 | PRINT Q4-FP wa To" oureurrere | pant @eee CONFIGURE for 20vee | PRINT @d-Re wr 708 Pat TRIGGER Contnveusy_ | PAINT @urTO™ woe To oureur rear | PRINT geo" SUFFKES rave | PRINT evr" wn 700" ourrurromy | PRINT @e GeTOstassute INPUT Ge. AAS | eaTOAAAS More 1) | ENTERTOGAAS (te) | INPUT SEAS int Deve acute | PRINT Aas masa PRINT AAS tow?) | PRINT AAS Notes: 1. Betoreusing AS on the 9626 is necessary to enter “dim AS[6)"toallocateastring variable. This statement allows sixcharacters. 2 IntheHP9e16 system, SCRATCH (Hit “EXEC” key) 0 (hit “ENTER” key) 20S (Hit "ENTER" key) 30END (Hit “ENTER key) (Hit"RUN” key) ‘This program creates the variables 1 program is not necessary for the HP-85 Calculator. riables cannot be created from the keyboard; they must be created by running a program. (Seeerror 810 for that system.) To get around this, type in a very short program as follows: and ‘AS’ so that they may be accessed in immediate mode and changed at will. This 3-58, TIMING CONSIDERATIONS To help you take the best advantage of the speed of the 8840A, external trigger timing for the IEEE~488 Interface is described in the specifications in Section 1. 3-59, IMMEDIATE MODE COMMANDS ‘Many controllers have some amount of “immediate mode” capability. That is, commands may be given interactively to the 840A via the run-time-system without the need for actually running @ program. The controller accepts and executes these commands one at a time. Some commonly used commands are listed in Table 3-3 for several con- ‘wollets. These ate provided for the convenience of instru- ‘ment demonstrations, set-up and check-out, and for those” with limited experience with IEEE-488 bus operations. As a general note: The entire 840A command set should ‘work well provided the “port clear” and “device clear” commands are given first. You should then be able to send. any other commands in the 8840A command set without Tepeating the clearing commands. 3-60. EXAMPLE PROGRAMS Several example programs for the 8840A using various ‘controllers are presented in the remaining figures in this section. In all of these examples, the 8840A is set to IEEE~488 address 4 (rear pane! switch setting 000100). Of course, any other address (00 10 30) could be substituted. In each of these examples, the instrament is cleared prior to configuration set-ups. ‘This ensures that the 8840 configuration has been completely defined. To run these programs, it is not necessary to type in all the comments (which appear to the right of the exclamation marks). Also, spaces are placed between commands for ease of reading; they are not required. NOTE For the examples using the Fluke 1720A or 17224, the 8840A is plugged into port 0. The ‘port is initialized by the INIT statement, which sends IFC (interface clear). g21ote mi Bam rosea u 21 3! 4! 5! 6 n 8 o 35 45 50 55 ‘This program selects VDC (F1), Autorange (RO), Slow rate (SO), continuous trigger (TO) and suffixes enabled (¥1). The program takes 10 readings and stops. The 8840A is addressed on Port 0, device #4 under control of a Fluke 1720A or 1722A Instrument Controller. In the INPUT statement, the controller assigns the first part of the 8840A ourput response (the measurement value) to R, and assigns the second part (the suffix) to RS. FLUKE-BASIC on 1720, 17224 INIT PORT 0 ‘Clear Port CLEAR PORT 0 ‘Clear instr to default functions PRINT @4, 'F1 RO SO TO YI" {Write functions to instrument FORI = 17010 INPUT @4, R, RS !Get data from 88404, PRINT" — "LRRS {Print to 1722A display NEXT END 3:22 Figure 3-10. Example Program: Taking 10 Readingsrence reins This is a sample program which commands the 8840A to the state of VDC, autorange, slow rate, continuous trigger and suffixes enabled. All readings appear simultaneously on the 3! instrument display while being logged on the controller display with suffixes enabled for 4! function readout. Full local control is given to the 8840A so that any range or function S!_ may be invoked easily. The controller always echos the 8840A display while this program 6! is running. 7 8 FLUKE-BASIC on 1720A, 1722 o 30 INIT PORT 0 lear Port 40 CLEAR PORT 0 lear instrument to default functions 50 WAIT 1000 !Wait 1 second before sending commands 60 PRINT @4, "F1 RO SO TO YI" 1F1=VDC, RO=Autorange, S0=Slow rate 701 !T0=Continuous trigger, Y1=Enable suffix 80 X=0 90 LOCAL @4 Give local contro! to instrument 951 110 INPUT @4,A,A$ SGet reading and suffix from 840A 120 X=X+1 Hncrement reading count 130 PRINT KAAS !Display reading and suffix 140 GOTO 110 200 END Figure 3-11. Example Program: Taking Readings with Local Control 323Remote Programming EXAMPLE PROG! 1 The following program illustrates one possible use of the serial poll register. In this ! case it is merely looking for data available. The instrument is addressed on port 0, device #4 under control of a Fluke 1720A or 172A instrument controller. The function Hof this program is to display on the controller screen the lowest resistance measured across the input terminals of the 8840A using the 2-wire ohms function in autorange. ‘The command string sets up the 8840A by using the Put Instrument Configuration command PO, FLUKE-BASIC on 1720A, 1722A 100 INIT PORT 0 \ CLEAR PORT 0 \ WAIT 500 IClear port, instrument, delay 110 PRINT @4, "N3001P0 Y1 7" ‘Mnstrument functions and trigger 120 INPUT @4, AAS {Get first reading 130 PRINT" —",A,AS;"S (2-wire) Lowest Reading” 140 TRIG @4 160 B%=SPL(4) Get serial poll register 170 IF (B%=0%) THEN 160 ‘Looking for data available 175 INPUT @4,RAS SGet next data 180 IF R>=A THEN 140 ‘Throw away data if not lowest 185 A=R {Update lowest reading 190 GoTo 130 {Print new low 900 END 324 Figure 3-12. Example Program: Using the Serial Poll RegisterRemote Programmin Sain! prooRS 30! This program demonstrates a method of recording any errors produced by the 8840A during self test. 20! 30! It should be noted that: 40! 1. If more than one digital test error occurs, only the last one will be reported. 50! 2. The response to the Get Instrument Configuration (GO) command during selftest is “Saxx". 60! 3. The response to a Get Error Status (G7) command with no errors present is "1000". 70! 80! FLUKE-BASIC on 1720A, 172A 90! 100 DA%=4% Wevice address #4 110 TIMEOUT 10000 10 second timeout 120 PRINT 130 PRINT "MONITORING SELFTEST" 140 INIT PORT 0 Unitialize port 150 CLEAR @DA% !Clear device 160 PRINT @DA%, "ZO" Start selftest 1701 180 PRINT @DA%, "G7" \ INPUT @DA%, ES 190 IF (ES = 1000") THEN 220 200 PRINT @DA%, "XO" 210 PRINT "ERROR ";RIGHT(ES,3);" OCCURRED" 220 PRINT @DA%, "GO" \ INPUT @DA%, STS. 230 IF (STS >= *9000") GOTO 180 240 PRINT @DAM%, "G7" \ INPUT @DA%, ES. 250 IF (E$ = "1000") THEN 270 260 PRINT "ERROR *;RIGHT(ES,3);" OCCURRED" 270 PRINT *SELFTEST COMPLETE" 280 END {Print analog errors {Print last digital error Figure 3-13. Example Program: Record Errors During Selttest 3:25Remote Programming EXAMPLE PROGRAMS 10 REM The following application program is written in BASICA for the IBM PC, PC-XT or 20REM PC-AT. The National Instruments Model GPIB-PCIIA board provides the interface 30 REM between the PC and the Fluke 8840A DMM. The program assumes that the configuration 40 REM program IBCONF has been nun to initialize the interface board with the device ‘50 REM name 18840A assigned to the GPIBO board. 60 REM 70 REM The first 6 lines of code are required to properly link the NI drivers to BASICA. 80 REM 90 REM 100 REM This program selects VDC (F1), Autorange (RO), Slow rate (SO), Continuous trigger (TO) 110 REM and suffixes enabled (¥1). The program takes 10 readings, displays them on the screen, 120 REM and then stops. 130 REM 140 REM 150 CLEAR ,59736! 160 IBINIT1 = 597361 170 IBINIT2 = IBINIT1 + 3 180 BLOAD "bib.m*JBINIT1 190 CALL IBINIT1 (BFIND,IBTRG,IBCLR,IBPCT JBSIC,IBLOG,IBPPCIBBNA IBONL,IBRSC,IBSRE, IBRSV,IBPAD,IBSAD, BIST, IBDMA IBEOS IBTMO.IBEOT IBRDF,IBWRTF) 200 CALL IBINIT2(IBGTS IBCAC,IBWAIT, IBPOKE,IBWRT,IBWRTA,IBCMD,IBCMDA IBRD IBRDAIBSTOP, IBRPP IBRSP,IBDIAG IBXTRC,IBRDI,IBWRTI IBRDIAIBWRTIA,IBSTA% IBERR%,IBCNT) 210 REM 220 REM IBM BASICA on IBM PC, PC-XT or PC-AT 230 REM ‘240 DEVNAMES="18840A" ‘Device name is 188404 250 CALL IBFIND(DEVNAMES,DVM%) “Initialize the DMM 260 CALL IBCLR(DVM%) "Clear the device 270 FOR W=1 TO 500 : NEXT W "Wait 1 second before sending command 280 WRTS="FIROSOTOY1" 290 CALL IBWRT(DVM%,WRTS) "Write functions to instrument 300 FOR I = 1 TO 10 310 RDS=SPACES(18) "11 characters for the reading, 5 for the 320 "suffix and 2 for the terminators 330 CALL IBRD(DVM%,RDS) "Get data from 8840A 340 PRINT I, LEFTS(RDS,16) ‘Print to display 350 NEXT I 360 END 1BM®, IBM PC, PO-XT and PC-AT are registered trademarks of International Business Machine Corporation ‘National instruments? is a registered trademark of National Instruments Corporation Figure 3-14. Example Programs: Using the IBM PC® 3-28Remot it me See Peo 10 REM The following application program is written in BASICA for the IBM PC, PC-XT or 20 REM PC-AT. The National Instruments Model GPIB-PCIIA board provides the interface 30 REM between the PC and the Fluke 8840A DMM. The program assumes that the configuration 40 REM program IBCONF has been run to initialize the interface board with the device 50 REM name I8840A assigned to the GPIBO board. 60 REM 70 REM The first 6 lines of code are required to properly link the NI drivers to BASICA. 80 REM 90REM This program illustrates one possible use of the serial poll register. In this 100 REM case it is merely looking for data available. The function of the program is to 110 REM display on the screen the lowest resistance value measured on the input terminals 120 REM of the 8840A using the 2-wire ohms function in autorange. ‘The range and function 330 REM commands are programmed using the Put Instrument Configuration (PO) command, 140 REM 150 CLEAR ,59736! 160 IBINIT? = 59736! 370 IBINIT2 = IBINIT1 + 3 180 BLOAD "bib." IBINITI 190 CALL IBINIT1 (BFIND,IBTRG IBCLR,IBPCT JBSIC,IBLOC,IBPPC, IBBNA,IBONL,IBRSCIBSRE, IBRSV,IBPAD,IBSAD,IBIST,IBDMA,IBEOS,|BTMO IBEOT IBRDF IBWRTF) 200 CALL IBINIT2(IBGTS,IBCAC,IBWAIT IBPOKE,IBWRT, IBWRTA,IBCMD,IBCMDA IBRD IBRDA IBSTOP, IBRPP,IBRSP,IBDIAG, IBXTRC,IBRDI,IBWRTI,IBRDIAJBWRTIAIBSTA%,IBERR%,IBCNT9%) 210 REM 220 REM IBM BASICA on IBM PC, PC-XT or PC-AT 230 REM 240 DEVNAME="18840A" ‘Device name is 18840A 250 CALL IBFIND (DEVNAMES,DVM%) “Initialize the DMM 260 CALL IBCLR. (DVM%) "Clear device 270 FOR W = 1 TO 500: NEXT W "Wait 1 second before sending commands 280 WRTS = "N3001P0 Y1 2" 290 CALL IBWRT (DVM%,WRTS) ‘Write functions to instrument 300 RDS = SPACES(18) 11 characters for the reading, 5 for the 310 “suffix and 2 for the terminators 320 CALL IBRD (DVM%,RDS) °Get first reading from 8840A 330 R = VAL(RDS) 340 PRINT LEFTS (RDS, 16);"S (2-WIRE) LOWEST READING" ‘Display readings 350 WRTS = "7" 360 CALL IBWRT (DVM%,WRTS) "Trigger the 8840A 370 CALL IBRSP (DVM%,SPR%) ‘Get serial poll byte 380 IF SPR% AND &H40 <> &H40 THEN 370 ‘Check for data available 390 RDS = SPACES(18) 400 CALL IBRD (DVM%,RDS) ‘Get next data 410 S = VAL (RDS) 420 IF S >= R THEN 350 “Throw away data if not lowest 430R = S "Update lowest reading 440 GOTO 340 ‘Print new low 450 END Figure 3-14. Example Programs: Using the IBM PC® (cont) 327Remote Programming 10 REM The following application program is written in BASICA for the IBM PC, PC-XT or 20 REM PC-AT. The National instruments Model GPIB-PCIIA board provides the interface ‘30 REM between the PC and the Fluke 8840A DMM. The program assumes that the configuration 40 REM program IBCONF has been run to initialize the interface board with the device 50 REM name 18840A assigned to the GPIBO board. 60 REM 70 REM The first 6 lines of code are required to properly link the NI drivers to BASICA. 80 REM 90 REM This program selects VDC (F1), Autorange (RO), Slow rate (SO), Continuous trigger (TO) 100 REM and suffixes enabled (¥1). All readings appear simultaneously on the instrument 110 REM display and the PC screen with suffixes enabled for function readout. Full local 120 REM control is given to the 8840A. Note the local control must be given to the board 130 REM and not the device. Press BREAK to terminate this program. 140 REM 150 CLEAR ,59736! 160 IBINIT1 = 59736! 170 IBINIT2 = IBINIT1 + 3 180 BLOAD *biban*JBINIT1 190 CALL IBINIT1 (BFIND,IBTRG,IBCLR,IBPCT,IBSIC BLOC, IBPPC,IBBNA IBONL IBRSC,IBSRE, IBRSV,IBPAD IBSAD JBIST,IBDMA [BES IBTMO,IBEOT.IBRDF IBWRTF) 200 CALL IBINIT2(BGTS,IBCAC, BWAIT,IBPOKE,IBWRT,IBWRTA,IBCMD, IBCMDAJBRD,IBRDAIBSTOP, IBRPP,IBRSP,IBDIAG IBXTRC,IBRDI,IBWRTLIBRDIAIBWRTIA IBSTA% IBERR%,IBCNT%) 210 REM 220 REM IBM BASICA on IBM PC, PC-XT or PC-AT 230 REM 240 BDNAMES="GPIBO" name is GPIBO 250 CALL IBFIND (BDNAMES,BD%) the interface board 260 DEVNAME="18840A" ‘Device name is 18840A 270 CALL IBFIND (DEVNAMES,DVM%) “Initialize the DMM. 280 CALL IBCLR. (DVM%) "Clear device 290 FOR W = 1 TO S00: NEXT W "Wait 1 second before sending commands 300 WRT$ = "FIROSOTOYi" 'F1=VDC, RO=autorange, SO=slow rate 310 ‘TO=continuous trig., Y1=enable suffix 320 CALL IBWRT (DVM%,WRTS) Write functions to instrument 330 CALL IBLOC (DVM%) "Give local control to instrument 340 V% = 0: X% = 0 350 CALL IBSRE (BD%,V%) ‘Deassert the remote enable (REN) 360 ’so the 8840A stays in local when a call 370 ‘to IBRD is made 380 RDS = SPACES(18) "11 characters for the reading, 5 for the 390 ‘suffix and 2 for the terminators 400 CALL IBRD (DVM%,RDS) "Get data from 8840A 410 X% = X% +1 420 PRINT X%, LEFTS (RDS,16) ‘Display readings 430 GOTO 380 440 END 3-28 Figure 3-14. Example Programs: Using the IBM Pc® (cont)rene cepoeaieg 10 REM The following application program is written in BASICA for the IBM PC, PC-XT or 20 REM PC-AT. The National Instruments Model GPIB-PCIIA board provides the interface 30 REM between the PC and the Fluke 8840A DMM. The program assumes that the configuration 40 REM program IBCONF has been run to initialize the interface board with the device SO REM name 18840A assigned to the GPIBO board. 60 REM 70 REM The first 6 lines of code are required to properly link the NI drivers to BASICA. 80 REM 90REM This program illustrates 2 method of recording any errors produced by the 840A 100 REM selftest function. It should be noted that: 110 REM 1. If more than one digital error occurs, only the last one will be reported. 120 REM 2. The response to a Get Instrument Config. (GO) command during selftest is "xxx", 130 REM 3. The response to a Get Error Status (G7) command with no errors present is "1000". 140 REM 150 CLEAR ,59736! | 160 IBINIT1 = 59736! 170 IBINIT2 = IBINIT1 + 3 180 BLOAD "bib.n"BINIT1 190 CALL IBINIT1 (BFIND,IBTRG,IBCLR,IBPCT IBSIC,IBLOC IBPPC,IBBNA IBONL,IBRSCIBSRE, IBRSV,IBPAD, IBSAD JBIST,BDMA,IBEOS IBTMO, IBEOT, IBRDF,IBWRTF) 200 CALL IBINIT2(BGTS,IBCAC IBWAIT,IBPOKE,IBWRT,IBWRTA,IBCMD IBCMDA,BRD IBRDAIBSTOP, IBRPP,IBRSP, IBDIAG,IBXTRC,IBRDI,IBWRTLIBRDIA IBWRTIA [BSTA% IBERR%,IBCNT%) 210 REM 220 REM IBM BASICA on IBM PC, PC-XT or PC-AT 230 REM 240 DEVNAME="18840A" "Device name is 18840A 250 CALL IBFIND (DEVNAMES,DVM%) “Initialize the DMM 260 CALL IBCLR (DVM%) "Clear device 270 FOR W = 1 TO S00: NEXT W "Wait 1 second before sending commands 280 PRINT "MONITORING SELFTEST 290 WRTS = "ZO" : CALL IBWRT (DVM%,WRTS) "Start selfrest 300 WRTS = "G7" : CALL IBWRT (DVM%,WRTS) 310 ES = SPACES(6) 320 CALL IBRD (DVM%ES) "Read error status 330 IF (LEFTS(ES,4) = "1000") THEN GOTO 360 "Check for errors 340 WRTS = "XO" : CALL IBWRT (DVM%, WRTS) ‘Clear error register 350 PRINT "ERROR ";RIGHTS(ES,3);" OCCURRED" Print analog error 360 WRTS = "GO" : CALL IBWRT (DVM%,WRTS) "Get instrument configuration 370 STS=SPACES(6) 380 CALL IBRD (DVM%STS) 390 IF LEFTS(STS,4) >= "9000" THEN GOTO 300 _—’Check for selftest still active 400 WRTS = "G7" : CALL IBWRT (DVM%,WRTS) 410 ES = SPACES(6) 420 CALL IBRD (DVM%,ES) "Read error status 430 IF (LEFTS(ES,4) = "1000*) THEN GOTO 450 "Check for errors 440 PRINT "ERROR ";RIGHTS(ES,3);" OCCURRED" Print digital error 450 PRINT 460 PRINT "SELFTEST COMPLETE" 470 END Figure 3-14, Example Programs: Using the IBM PC° (cont) 2429Remote Programming EXAMPLE PROGRAMS ‘The following application program is written in QBASIC for the IBM PC, PC-XT or PC-AT. The National Instruments Model GPIB-PCIIA board provides the interface between the PC and the Fluke 8840A DMM. The program assumes that the configuration program IBCONF has been run to initialize the interface board with the device name 18840A assigned to the GPIBO board. This program selects VDC (F1), Autorange (RO), Slow rate (SO), Continuous trigger (TO) and suffixes enabled (Y1). The program takes 10 readings, displays them on the screen, and then stops. Microsoft QuickBasic V 4.5 on IBM PC, PC-XT or PC-AT °SINCLUDE: ‘gbib45.dcl" devname$ = "18840A" ‘Device name is 188408. CALL IBFIND(demnameS, dvm%) ‘Initialize the DMM CALL IBCLR(dvm%) "Clear device WRITS = "FIROSOTOY1" °Set up command string CALL IBWRT(dvm%, WRTS) "Write functions to instrument FORi = 17010 RDS = SPACES(18) "11 characters for the reading, 5 for “the suffix, and 2 for terminators CALL IBRD(dvm%, RDS) ‘Get data PRINT i, LEFTS(RDS, 16) ‘Print to display NEXT i END Microson® is a registered trademark of Microsoft Corporation (QuickBASIC™ isa trademark of Microsoft Corporation Figure 3-14. Example Programs: Using the IBM PC® (cont)Remote Programming ‘Saurus proces The following application program is written in QBASIC for the IBM PC, PC-XT or PC-AT. The National Instruments Model GPIB-PCIIA board provides the interface between the PC and the Fluke 8840A DMM. The program assumes that the configuration program IBCONF has been run to initialize the interface board with the device mame 18840A assigned to the GPIBO board. This program selects VDC (F1), Autorange (RO), Slow rate (SO), Continuous trigger (TO) and suffixes enabled (¥1). All readings appear simultaneously on the instrument | display and the PC screen with suffixes enabled for function readout. Full local control is given to the 8840A. Note the local control must be given to the board and not the device. Press BREAK to terminate this program. Microsoft QuickBasic V 4.5 on IBM PC, PC-XT or PC-AT "SINCLUDE: ‘qbib45.del’ BDNAMES = "GPIBO" ‘Board name is GPIBO | CALL IBFIND(BDNAMES, BD%) “Initialize IEEE Interface Board demnames = "188404" "Device name is 18840A CALL IBFIND(devnameS, dvm%) “Initialize the device CALL IBCLR(dvm%) ‘Clear the device WRTS = "FIROSOTOY1" 'F1 = Volts DC, RO = Autorange, °SO = Slow reading rate, TO = Intemal “Trigger, Y1 = Enable suffix CALL IBWRT(évn%, WRTS) "Write functions to the instrument CALL IBLOC(dvm%) "Give local control to the instrument ‘Vo = 0: 39% = 0 CALL IBSRE(BD%, V96) ‘De-assert the remote enable (REN) signal so “the 8840A stays in local when an IBRD call ‘is made RDS = SPACES(18) "11 characters for the reading, § for the ‘suffix and 2 for the terminators CALL IBRD(dvm%, RDS) ‘Get data X% = x% +1 "Increment reading count PRINT x%, LEFTS(RDS, 16) ‘Display reading GOTO again END Figure 3-14. Example Programs: Using the IBM Pc® (cont) 331Remote Programmi Baus prota no 3-32 label: ‘The following application program is written in QBASIC for the IBM PC, PC-XT or PC-AT. The National Instruments Model GPIB-PCIIA board provides the interface between the PC and the Fluke 8840A DMM. The program assumes that the configuration Program IBCONF has been run to initialize the interface board with the device name 18840A assigned to the GPIBO board. ‘This program illustrates one possible use of the serial poll register. In this case it is merely looking for data available. The function of the program is to display on the screen the lowest resistance value measured on the input terminals of the 8840A using the 2-wire ohms function in autorange. The range and function commands are programmed using the Put Instrument Configuration (PO) command. Microsoft QuickBasic V 4.5 on IBM PC, PC-XT or PC-AT *SINCLUDE: ‘qbib45.de? bdname$ = *GPIBO" “Board name is GPIBO CALL IBFIND(bdnames, BD%) “Initialize the Interface Board devnameS = 188404" ‘Device name is 188408 CALL IBFIND(devnames, dvm%) “Initialize the device CALL IBCLR (dvm%) “Clear the device ‘WRTS = "N3001P0 Y1 ?" CALL IBWRT(évin%, WRTS) "Write functions to the instrument RDS = SPACES(18) ‘CALL IBRD(avm%, RDS) °Get first reading r = VAL(RDS) PRINT LEFTS(RDS, 16); *S (2-WIRE) LOWEST READING" Do “Execute the statements up to the loop “statement until new low is found ‘WRITS = "7" CALL IBWRT(évm%, WRTS) “Trigger the device SPR% = 0 DO UNTIL SPR% AND &H40 = 84140 CALL IBRSP(dvm%, SPR%) “Serial poll the device until data available Loop RDS = SPACES(18) CALL IBRD(dvm%, RDS) "Get next data 3 = VAL(RDS) LOOP WHILE s >= r “Throw away data if not lowest rs "Update lowest reading GOTO label 'Print new low END Figure 3-14, Example Programs: Using the IBM PC° (cont)mote Programming Femets cre od The following application program is written in QBASIC for the IBM PC, PC-XT or PC-AT. The National Instruments Model GPIB-PCIIA board provides the interface between the PC and the Fluke 88404 DMM. The program assumes that the configuration Program IBCONF has been run to initialize the interface board with the device name 18840A assigned to the GPIBO board. This program illustrates a method of recording any errors produced by the 840A. selftest function. It should be noted that: 1. If more than one digital error occurs, only the last one will be reported. 2. The response to a Get Instrument Config. (GO) command during selftest is "xx". . The response to a Get Error Status (G7) command with no errors present is "1000". Microsoft QuickBasic V 4.5 on IBM PG, PC-XT or PC-AT "SINCLUDE: 'qbib45.del” BDNAMES = *GPIBO" ‘Board name is GPIBO CALL IBFIND(BDNAMES, BD%) “Initialize the interface board devname$ = "188404" ‘Device name is 18840A CALL IBFIND(devnameS, dvm%) ‘Initialize the device PRINT "MONITORING SELFTEST" WRITS = "Zo" CALL IBWRT(dvm%, WRTS) "Start selftest Do WRIS = "G7" CALL IBWRT(dvm%, WRTS) RDS = SPACES(18) CALL IBRD(dvm%, RDS) Get error status errcode$ = LEFTS(RDS, 4) IF (errcode$ <> 1000") THEN "Check for errors WRIS = "XO" "Clear error register CALL IBWRT(dvm%, WRTS) PRINT "Error "; RIGHTS (errcode$, 3); * occurred” END IF CALL IBWRT(dvm%, "GO") st$ = SPACES(16) CALL IBRD (dvm%, st$) ‘Get instrument configuration stat$ = LEFTS(stS, 1) LOOP WHILE stat$ = "9" ‘Loop while selftest still active WRTS = "G7" CALL IBWRT(dvm%, WRTS) RDS = SPACE$(18) CALL IBRD(dvm%, RDS) “Get error status exrcodeS = LEFTS(RDS, 4) IF (errcode$ <> *1000") THEN "Check for errors PRINT "Error"; RIGHTS(errcodeS, 3); * occurred” END IF PRINT PRINT "Selftest Complete” END Figure 3-14. Example Programs: Using the IBM Pc (cont) 333mote innit Soot epmemie /* The following application program is written in C for the IBM PC-AT. ‘The National Instruments Model AT-GPIB board provides the interface between the PC and the Fluke 8840A DMM. The program assumes that the configuration program IBCONF has been run to initialize the interface board with the device name I8840A assigned to the GPIBO board. This program selects VDC (FI), Autorange (RO), Slow rate ($0), Continuous trigger (10) and suffixes enabled (YI). The program takes 10 readings, displays them on the screen, and then stops. Microsoft C Version 6.0 on IBM. PC-AT ” /* Link this program with appropriate meib*.ob. ” #include #include “decLh* char rd{512]; 7 read data bulfer ” int dmm; 7* device number 7 int i main() { dmm = ibfind(188404"); /* device name is 18840 ” ibeir(émm); /* clear device ” ibwrt(émm,"FIROSOTOY1",10); 7/* write functions to instrument ” for(i=0;i<10;i++) ‘{ibrd(émm,rd); /* get data ” pring C%d%s".rd); 7* print to display ” } > 304 Figure 2-14, Example Programs: Using the IBM PC°(cont)Remote mit Saute PROSRe | The following application program is written in C for the IBM PC-AT. ‘The National Instruments Model AT-GPIB board provides the interface between the PC and the Fluke 840A DMM. ‘The Program assumes that the configuration program IBCONF has been run to initialize the interface board with the device name 18840A assigned to the GPIBO board. This program selects VDC (F1), Autorange (RO), Slow rate (S0), Continuous trigger (TO) and suffixes enabled (¥1). All readings appear simultaneously on the instrument display and the PC screen with suffixes enabled for function readout. Full local control is given to the 8840A. Note the local control must be given to,the board and not the device. Press C to terminate this program. Microsoft C Version 6.0 on IBM PC-AT 7 Link this program with appropriate mcib*.obj. ” #indlude #include “decl.h* char rd{512); /* read data buffer ” int brdo; /* interface board number y int dmm; /* device number 7 int x ‘main( ) { brdo = ibfind('GPIBOY); */ dmm = ibfnd(1gs40a); /* initialize device 7 ibelr(¢mm); 7? clear device ” ibwrt(dmm,"F1ROSOTOY1",10); /* write functions to instrument 7 ibloc(émm); 7* local the device 7 ibsre(brd0,0); /* de-assert the remote enable (REN) signal so the */ /* 88404 stays in local when an ibrd call is made */ x=0; in: ibrd(dmm,rd); 77 get data ” x=x+]; /* increment reading count 7 print{(%d — %s",x,rd); /* display readings 7 goto in; } Figure 3-14, Example Programs: Using the IBM PC°(cont) 33sRemote jrammin; Baume erooeas * ‘The following application program is written in C for the IBM PC-AT. The National Instruments ‘Model AT-GPIB board provides the interface between the PC and the Fluke 8840A DMM. The program assumes that the configuration program IBCONF has been run to initialize the interface ‘board with the device name 18840A assigned to the GPIBO board. This program illustrates one possible use of the serial poll register. In this case it is merely looking for data available. ‘The function of the program is to display on the screen the lowest resistance value measured on the input terminals, of the 8840A using the 2-wire ohms function in autorange, The range and function commands are programmed using the Put Instrument Configuration (PO) command. ‘Microsoft C Version 6.0 on IBM PC-AT ” /* Link this program with appropriate meib*.obj. ” #include #include "decl.h” #include #include char rd{512}; /* read data buffer ” int brdo; /* interface board number Y int dmm; /* device number ” char spr; /* serial poll response byte ” float r,s; char rd_string{11],ss{11]; main( ) 4 brdO = ibfind( "GPIBO" ); ey) dmm = ibfind( 18840" ); /* initialize 88408 ” ibelr( dmm ); 7* clear device ” ibwrt( dmm, "N3001POY1?", 10); /* write fanctions to instrument ” ibré(dmm,rd,16); 7* get data ” stmepy(td_string,rd,11); r=atof(rd_string); /* convert from string to floating point */ label: printi('%sS (2-wire) LOWEST READING\\n‘rd); do { ibwrt(émm,"?*,1); (/* tigger the device ba /* serial poll the device +s ' 7* until data available ¥ ibrd(émm,rd,16); 7* get next data "7 ‘atof(rd); (/* convert to floating point ” printf(\"); + while (s>=0); /* throw away data if not lowest ” ras; goto labell; /* print new low ” 3:36 Figure 3-14. Example Programs: Using the IBM PC® (cont)Remote Programmit Saweie PaOSnAS rn The following application program is written in C for the IBM PC-AT. The National Instruments Model AT-GPIB board provides the interface between the PC and the Fluke 8840A DMM. ‘The Program assumes that the configuration program IBCONF has been run to initialize the interface board with the device name 18840A assigned to the GPIBO board. This program illustrates a method of recording any errors produced by the 8840A selftest function. It should be noted that: 1. If more than one digital error occurs, only the last one will be reported. 2. The response to a Get Instrument Config. (GO) command during selftest is *xxx". 3. The response to a Get Error Status (G7) command with no errors present is "1000", Microsoft C Version 6.0 on IBM PC-AT Link this program with appropriate mcib*.obj. #indude #indude "decl.h* #indude char rd[512); /* read data buffer int brdo; /* interface board number int dmm; /* device number char selftest_active[1}; /* selftest active flag char errcode{4]; /* error code buffer main() { brd0 = ibfind("GPIBO"); /* initialize interface board dmm = ibfind(18840A"); /* initialize 88404 ‘ibelr(dmm); /* clear device ibwrt(dmm,"Z0",2); (/* start 88404 self test dof 7* do while self test active ibwre(émm,'G7"2); 7* get error status ibrd(dmm,rd,16); strnepy(errcode,rd,4); if (suremp(errcode,"1000")!=0) /* test for error Aibwrt(dmm,"X0",2); printf(Error %s occurred\r\n",errcode); > ibwrt(dmm,'G0",2); /* get instrument configuration ‘ibrd(dmm,r4,16); strnepy(selftest_active,rd,1); + while (stremp(selftest_active,"9")==0); _/* check for self test active ibwrt(dmm,"G7"2); 7* get error status ibré(émm,rd,16); strnepy(errcode,rd,4); if (stremp(errcode,"1000")!=0) 7* test for last digital error printf("Error %s occurred\r\n",errcode); print{("\r\nSelftest complete\r\n"); + 7 ” 7 7 7 7 ” 7 ey, ” OF 7 he ” ” 7 ” ” Figure 3-14. 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INTRODUCTION This section discusses considerations and techniques to help you use the 8840A effectively. Among other things, this section discusses sources of error which are an inher- cent 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 contfi- dence. “This section also discusses the relative benefits of 2-wire and 4-wire ohms, describes special considerations for mak- ing ac measurements, and presents some unusual applications-for example, using the test current in the 2ewire ohms function as a troubleshooting tool in itself. 4-2. DC VOLTAGE MEASUREMENT When measuring de voltages in high-impedance circuits, there ate two possible sources of error to consider: circuit loading and input bias current. 4-3. Circuit Loading Error Whenever a voltmeter is connected to a circuit, the volt- meter's internal resistance changes the voltage of the circuit under test. The resulting error is called circuit loading error. The error is negligible as long as the resis- tance of the circuit under test (the source impedance) is small compared 10 the input impedance of the meter. As the source impedance approaches the input impedance of the voltmeter, the error can be considerable. The percent- age of error can be calculated using the formula in Figure #1. ‘The input impedance of the 8840A is 10 MQ in the 200V and 1000V ranges, and is greater than 10,000 MQ in the 200 mV, 2V, and 20V ranges. Therefore, for the 8840A, circuit loading error is less than 0.01% as long as the source impedance is less than 1 M&2 in the 200 mV, 2V, and 20V ranges, and less than 1 kQ in the 200V and 1000V ranges. The exceptionally high input impedance on the 20V de range allows high-accuracy readings in CMOS and high-impedance analog circuitry Section 4 Measurement Tutorial NOTE Input protection circuitry can reduce the input impedance to as low as 100 Q when the input is overrange. This may also occur momentarily when the instrument autoranges to a higher range. 4-4, Input Bias Current Error Input bias current error occurs because a voltmeter’s input bias current always changes the voltage of the circuit ‘under test, However, the error is significant only when measuring voltages ‘in circuits with very high source impedance. The error can be measured as shown in Figure 42, ‘With the 8840A, it is easy t0 correct for this error using the OFFSET button: 1. Select the VDC function and the desired range. 2. Connect the 8840A INPUT terminals to a resistor ‘which matches the source impedance of the circuit to be tested. Allow the displayed reading to setle. Press the OFFSET button. Remove the resistor. Proceed with the desired measurement aha Example: Measure a 1.5V source with 1 MQ source impedance, ‘correcting for input bias current 1. Connect a 1 MQ resistor between the INPUT HI and INPUT LO terminals. 2. Select the VDC function and the 2V range. Allow the display to settle, 4. Press OFFSET. (This zeroes the input bias current error) atMeasurement Tutorial DC VOLTAGE MEASUREMENT Ri i CIRCUIT LOADING ERROR IN % = 100%_Bs where Rs = Source impedance ii = 88404 input impedance -10,000 MQ in 200 mv, 2V, and 20V ranges) 10. MQ. in 200V and 1000V ranges) Rs FRI EXAMPLE 20 KA. SOURCE == Rg = (20M) x (10 KD) _ 9 ky 80 K2 + 10 kA When measuring the vottage across the 10 k® leg of a90 kM over 10 kA voltage divider, the circuit loading erroris less than 0.1% in the upper ranges, and less than 0.0001% in the lower ranges: “oy pe [3 Error in the 200V and 1000V ranges = 100 x Tens TOM = 0.0% ane 9ko Error in the 200 mV, 2V and 20V ranges = 10x = —S 6B 9kO .00009% Figure 4-1. Circuit Loading Error Calculation 5. Remove the 1 MQ resistor. 6 Measure the voltage of the circuit under test. Note that this procedure does not correct for circuit load- ing error. Also note that if input bias current error is not corrected for, it may be added to the circuit loading error. 45. RESISTANCE MEASUREMENT : The 8840A allows you to measure resistance in both 2-wire and 4-wire configurations. Each has its benefits. 46. 2-Wire Ohms ‘Two-Wire ohms measurements are simple to set up and yield good results for most measurement conditions. Mea- ‘surements are made as shown in Figure 4-3. An intemal current source (the “ohms current source”) passes a known test current (ltest) through the resistance being tested (Runknown). The 8840A measures the voltage drop across Runknown, calculates Runknown using Ohm’s law (unknown = Viest/itest), and displays the result. 42 The test current and full-scale voltage for each resistance ange are shown in Table 4-1. Since the HI INPUT test lead is positive with respect to the LO INPUT lead, these test leads ate not interchangeable when a semiconductor device is being measured. 4-7. Comecting for Test Lead Resistance in 2-Wire Ohms: In 2-wire obms, the resistance of the test leads can introduce error when measuring low resistances. Typical test leads may add as much as 0.5Q to 2-wire ohms readings. ‘With the 88404, it is easy to correct for this error using the OFFSET button: 1. Select the 2-wite ohms function. 2. Touch the test leads together. The 8840A should indicate the resistance of the test leads.Measurement Tutorial [RESISTANCE MEASUREMENT Reounce TO MEASURE INPUT BIAS CURRENT ERROR: 1. Select the VDC function and the desired range. OFFSET. the HI INPUT and LO. INPUT terminals. 4, Allow the circuit to settle. ERROR (IN %) = tans = 2. Eliminate any offset voltages by shorting the HI INPUT and LO INPUT terminals and then pressing Selecta resistor which matches the source impedance (Rsourcs) of the circuitto be tested, and connect itto 5. Record the displayed voltage. This is the input bias current error (Vermce). ‘The input bias current error may be calculated as @ percentage as follows: ‘The input bias current itself (Inias) may be calculated as follows: Vewwce Reounce 88404, Vexnon VOLTAGE MEASUREMENT * 100% Figure 4-2. Measuring Input Bias Current Error 3. With the test leads still touching, press the OFFSET button. The 8840A should read 02. 48. 4-Wire Ohms Four-Wire ohms measurements provide the highest accuracy for low resistance measurements. The 4-wire configuration automatically corrects for both test lead resistance and contact resistance. Contact resistance (the resistance between the test probe tips and the circuit being tested) is unpredictable, and therefore cannot be reliably corrected with a fixed offset. Four-Wire ohms measurements are especially important when using long test leads. In a typical automated test system, for example, the test leads could. be connected ‘through four or five switching relays, each with 20 of resistance! ‘The 8840A makes 4-wire ohms measurements as shown in Figure 4-4. The HI and LO INPUT leads apply a known, internal current source to the unknown resistance, just 2 in 2-wite ohms. (See Table 4-1.) However, the voltage top across the unknown resistance is measured with the SENSE leads rather than the INPUT leads. Since the ‘current flow in the SENSE leads is negligible, the error ‘caused by the voltage drop across the leads is also negligi- ble. NOTE In the 2 MQ and 20 MQ ranges of 4-wire ‘ohms, the voltage across the unknown resis- tance is sensed beoween the HI SENSE and LO INPUT terminals. Accuracy is not affected as long as the resistance of the LO INPUT lead is less than 102 in the 2 MQ range, and less than 1002 in the 20 MQ range. 4-9, Applications of the Ohms Functions ‘The 2-wire and 4-wire ohms functions can be used for a variety of purposes in addition to measuring resistance, as the following applications show. 43Measurement Tutorial RESISTANCE MEASUREMENT HI INPUT! Table 4-1. Ohms Test Current Rance | cunment | "Woutaae ae + mA ov 2k tm 2av 20 Ko 100 4A 2ov 20 2 10 wa 2ov amos | SA tov 20 No 500 nA toov 4-10. TESTING DIODES ‘The 2-wire ohms function can also be used to test diodes. 1, Select the 2-wire ohms function and the 2 k@ range. 2. Measure the resistance of the diode. If the diode is 00d, when forward-biased it will measure about 0.6 KQ to 0.7 kQ for silicon (0.25 KQ to 03 KQ for germanium), and when reverse-biased it will cause the S840A to indicate overrange. (The forward-biased reading depends upon the range used.) ‘The 2 kQ range is used because its 1 mA test current provides 2 typical operating point, and its 2V full-scale voltage is sufficient to tum on most diodes (even two odes in series). 4-11. TESTING ELECTROLYTIC CAPACITORS ‘The 2-wire ohms function can also give a rough test of an electrolytic capacitor’s leakage and dielectric absorption. This test works well for capacitors 0.5 uF and larger. 44 ‘OHMS CURRENT SOURCE L Figure 4-3. 2-Wire Ohms Measurement Select the 2-wire ohms function, the 2 k@ range, and the medium reading rate. Connect the test leads to the capacitor (with the INPUT HI lead to the + lead and the INPUT LO lead to the - lead). The 8840A will try to charge it to the ‘open-circuit voltage of the 2 kQ range (about 6V). Disconnect the + test lead. To test for leakage, select the VDC function and the 20V range (leave the 8840A in the medium reading Tate), and measure the voltage that was stored on the capacitor during step 2. 1. If the capacitor is good, the voltage across the capacitor will be about 6V, and will be relatively stable. b. If the capacitor is leaky, the voltage across the capacitor will be much less than 6V, and the voltage will be decreasing. The rate of change depends on how leaky the capacitor is. ©. With some electrolytic capacitors, the reading will increase. This usually indicates the capacitor is defective. To test the capacitor's dielectric absorption, briefly short the capacitor’s leads together and then measure the voltage across the capacitor. a. If the dielectric is good (ie., has low dielectric absorption), the voltage across the capacitor will bbe neatly ze10 volts.Measurement Tutorial [RESISTANCE MEASUREMENT HI INPUT OHMS: Oe ssonee LO INPUT 88408, OHMS CURRENT SOURCE Punsiown HI SENSE DC VOLTAGE SENSING CIRCUITRY LO SENSE COINPUT exp (Four places) Figure 4-4. 4.Wire Ohms Measurement b. If the dielectric is poor (ie., has high dielectric absorption), the voltage across the capacitor will be significantly above zero 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. 1t has excellent linearity and temperature stability. Its compliance voltage is typically SV in the lower four ohms ranges, and 12V in the upper two ohms ranges. The inputs are protected against accidental applications of volt- ‘age up to 300V rms. To use the chms current source, connect the test leads to the HI and LO INPUTS, and select either the 2-wire or 4-wire ohms function. Press the range buttons to select any of the current levels shown in Table 4-1. ‘The ohms current source can be used to troubleshoot ireuits by injecting current into selected nodes, forcing the circuits to be in a specific test state. For example, the ‘ohms current source can be used to set or modify the bias of amplifier circuits. The current level can be changed simply by, changing range. ‘The ohms current source can also be used to test mA or A panel meters. The accuracy of the current source is ‘more than enough to verify panel meters, whose aecuracy is typically 1% to 5%. To test an analog panel meter, simply connect the current source across the meter| move- 45Measurement Tutorial RESISTANCE MEASUREMENT ment (as though measuring its resistance). A 1 mA meter should show full scale when the ohms function is set on the 2 kQ range. The same technique also works with digital pane! meters. 4-13. DC CURRENT MEASUREMENT To get the best accuracy using the mA DC function, it is imponant to understand the concept of burden voltage error. ‘When a meter is placed in series with a circuit to measure ‘current, error can be caused by the small voltage drop ‘cross the meter (in this case, across the protective fuses and current shunt). This voltage drop is called the burden voltage, and it is highest for full-scale measurements. The full-scale burden voltage for the 8840A is typically less than 1V. ‘The burden voltage can present a significant error if the ‘current source being measured is unregulzted (ie, not a ‘true current source) and if the resistance of the fuse and shunt is a significant part of the source resistance. If ‘burden voltage does present a significant error, the per- ‘centage of error can be calculated and corrected for using the formulas in Figure 4-5. 4-14, REDUCING THERMAL VOLTAGES ‘When making very low-level de 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 typi- cally occar at binding posts and can be greater than 10 nV. ‘Thermal voltages can also cause problems in the low ohms ranges. Some low-value resistors are constructed with dissimilar metals. Just handling such resistors can cause thermal voltages large enough to introduce measurement ‘errors. “The effect of thermal voltages can be reduced by using the following techniques: 1. Use tight connections. 2. Use clean connections (especially free of grease and dirt). 3. Use similar metals for connections wherever possible (€.84 copper-to-copper, gold-to-gold, etc.) 4, Use caution when handling the citcuit 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 46 those discussed under de voltage and current measurement. ‘These include the concepts of rms conversion, crest Factor, bandwidth, and zero-input error. 4-16. True RMS Measurement ‘The True RMS AC Option measures the true ms value of ‘ac voltages and currents. In physical terms, the rms (root- mean-square) value of a waveform is the equivalent de value that causes the same amount of heat to be dissipated in a resistor. True rms measurement greatly simplifies the analysis of complex ac signals. Since the rms value is the ec equivalent of the original waveform, it provides a reliable basis for comparing dissimilar waveforms. By contrast, many meters in use today use average responding ac converters rather than true rms converters. ‘The scale factor in these meters is adjusted so that they display the rms value for harmonic-free sinusoids. Howev- tif a signal is not sinusoidal, average-responding meters do not display correct rms readings. ‘The 8840A actually derives the rms value using analog computation. This means that the 840A readings fepre- sent true rms values not only for harmonic-free sinusoids, bbut also for mixed frequencies, modulated signals, square ‘waves, sawtooths, random noise, rectangular pulses with 10% duty cycle, etc. 4-17. Waveform Comparison Figure 46 illustrates the relationship between ac and de ‘components for common waveforms, and compares read- ings for true rms meters and average-responding meters. For example, consider the first waveform, a 1.41421V (2ero-to-peak) sine wave. Both the 8840A and] ms- calibrated average-responding meters display the correct sms reading of 1.00000V (the de component equals 0). However, consider the 2V (peak-to-peak) square wave. Both types of meter correctly measure the de component (OV), but only the 8840A correctly measures the ac|com- ponent (1.00000V). The average-responding meter meas- wes 1.110V, which amounts to an 11% error. 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. 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 10 its rms voltage. (For waveforms where the Positive and negative half-cycles have different peak vol- tages, the mote extreme peak is used in computing the crest factor.) Crest factors start at 1.0 for square waves (for which the peak voltage equals the rms voltage) andMeasurement Tutorial AC VOLTAGE ANO CURRENT MEASUREMENT ba EXAMPLE: Displayed current Correct current = 1460 mA + 40 mA = 1500 mA NOTE: MEASURING BURDEN VOLTAGE ‘measure voltage at the 2A terminal. ERROR IN mA = (Displayed current) X —=*— e ERROR IN PERCENT = =x 100 | 1460 mA Es = 18V (measured with 88404 in VDC function) E> = 0.4V (measured with 8840A as described below) Error in percent = 2% x 109 = 2.67% 15V Error in mA = (1460 mA) X | To get the correct current, add the error in mA to the displayed current: ‘The 8840A allows you to measure burden voltage (Es) directly. Leaving the 2A and LO INPUT leads in place for current measurement, select the VDC function. Then, connect a third lead to the Hi INPUT terminal and with it E:= Source voltage (measured) Es= Burden voltage (measured) Ri= Load + source resistance Re = 8840A internal resistance Ee Es av ON soma 18V-0.4V Figure 4-5. Burden Voltage Error Calculation increase for more “pointed” waveforms as shown in Figure 47. ‘The 8840A has a full-scale crest factor limit of 3.0 for the 20V and 700V ranges, and 6.0 for the other ranges. For full-scale input signals with a crest factor above these limits, dynamic range limitations can begin to cause large errors. However, as Figure 4-7 shows, signals with a crest factor above 3.0 are unusual, If you don’t know the crest factor of a particular waveform but wish to know if it falls within the crest factor limit of the 8840A, measure the signal with both the 8840A and an ac-coupled oscilloscope. If the rms reading on the 8840A is 1/3 or more of the waveform’s zero-to-peak voltage, the crest factor is 3.0 or less. 4-19, AC-Coupled AC Measurements Input signals are ac-coupled in the ac functions. One of the advantages of ac coupling is that ac measurements can be made on power supply outputs,- phone lines, etc. Ripple ‘measurements, for instance, cannot be made with de coup- ling. Remember, however, that when the 8840A measures signals with the ac functions, the reading on the display 47Measurement Tutorial ‘AC VOLTAGE AND CURRENT MEASUREMENT 48 PEAK VOLTAGES, METERED VOLTAGES DG AND AG ‘AC-COUPLED ‘AG COMPONENT ONLY pe TOTAL RMS wavetonn | PKPK | PK component | TAUE RS RMS CAL* 88408 ‘ONLY. Vactrac™ ‘SINE 4 | sa GAS 1.000 oO ay PK-PK 1.000 0.000 + 1.000 REGHREDSNE [yaa PUL Wave) ta oxi rine ovas + 0.900 1.000 RECTIFIED SINE | 2.000 (HALF WAVE) 2.000 oes med OTN sas SQUARE 2.000 rey 10 ato 1.000 ol PPK 0.000 1.000 | 1814 SQUARE 1414 0.785 p_PRPK over Tut om 1.000 RECTANGULAR: PULSE fd a “Aa ak ave F a D=XY k-VO-07 | TRIANGLE SAWTOOTH a 2D 1.782 pw 0.960 \) pe 1.000 inno — 1.000 ‘* RMS CAL IS THE DISPLAYED VALUE FOR AVERAGE RESPONDING METERS THAT ARE CALIBRATED TO DISPLAY RMS FOR SINE WAVES. Figure 4-3. Waveform Comparison ChartMeasurement Tutorial ‘AC VOLTAGE AND CURRENT MEASUREMENT does not include the de component (if one exists). For example, consider Figure 4-8, which shows a simple ac signal riding on a de level. The VAC function would ‘measure the ac component only. 420. Combined AC and DC Measurements ‘The 8840A can be used to evaluate the true rms value of waveforms such as the one shown in Figure 4-8, which includes both ac and de components. First, measure the rms value of the ac component using the VAC function. Next, measure the de component using the VDC function. Finally, calculate the total rms value as follows: Vas (Wit Va 4-21. Bandwidth Bandwidth defines the range of frequencies 1o which an instrument can sespond accurately. The accuracy of the 8840A is specified for sinusoidal waveforms up to 100 Kliz, or for nonsinusoidal waveforms with frequency com- ponents up to 100 kHz. The small-signal bandwidth (the frequency at which the response is 3 dB down) is typically around 300 kHz. For signals with components greater than 100 kHz, the ‘measurement accuracy is reduced because of frequency bandwidth and slew-rate limitations. Because of this, accuracy may be reduced when measuring signals with fast rise times, such as high-frequency square waves or switch- ing supply waveforms. As a rule of thumb, an ac voltage input signal is within the bandwidth limitations if the rise time is longer than 2 ys, and within the slew-rate limita- tions if the input slew rate is slower than (1V/us)xCull, seale of range). 4-22. Zero-Input VAC Error If the 8840A input terminals are shorted while the VAC function is selected, the 8840A displays a non-zero reading (ypically less than 80 digits in the highest four ranges, and less than 300 in the 200 mV range). Such readings are due to random noise combined with the inherent nonlinear response of computing-type ms con- verters to very small input signals. ‘The zero-input error is quickly reduced when the input is increased. The ms converter error (a de error) and the intemally 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. WAVEFORM REST FACTOR SOUARE WAVE 1a SINE WAVE VY isis TRIANGLE mss, A, |e FREQUENCIES 1.414 10 20 son auteur warenose ANWYAK | 20040 accoueo [LIL] a ¢ feral Figure 47. Typical Crest Factors for Various Wave- forms ‘AC COMPONENT | DC COMPONENT Figure 4-8. Combined AC and DC Measurement As long as the 8840A reading is 1,000 counts or moze, readings will still be within specified accuracy.Measurement Tutorial ‘AG VOLTAGE AND CURRENT MEASUREMENT EXAMPLE Given a zero-input reading of 300 counts (0.900 mV in the 200 mV range) andaan input signalot 10 mV, the B840A might read: Vy 1% + 0300! = -/ 100+ 0.000 = 10.004mv ‘The etfect of the zero-input error is reduced from 0.300 mV to 0.004 mV. Figure 4-9, Reduction of Zero-input Error 4-105-1. INTRODUCTION This section presents an overall functional description of the 88404, 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 8840A. is shown in Figure 5-1. The basic signal path flows from left to right ‘across the center of the page. The input is sensed at the input terminals, scaled, directed through the Track/Hold circuit, converted into digital representation by the Analog-to-Digital (A/D) Converter, processed by the Dig- ital Controller, and sent to the display. ‘The DC Scaling circuit, which constitutes the “front end” Of the instrument, has two major functions. First, it senses the input and produces an equivalent dc voltage for all functions except VAC and mA AC. (AC inputs are con- verted to a de voltage by the True RMS AC Option.) Resistances are sensed as a dc voltage using a known test ccurrent from the Ohms Current Source. A de current input is converted to a de voltage by a precision current shunt. Second, the DC Scaling circuit scales the equivalent de voltages (for in-range inputs) to within the input range of the A/D Converter (22V). In addition, the DC Scaling Circuit provides input protection and provides analog filter- ing for certain ranges and reading rates. (AC inputs are sealed by the True RMS AC Option) ‘The Track/Hold (T/H) circuit samples the scaled de volt- age and presents the A/D Converter with a voltage that is, constant for the input portion of each A/D conversion cycle. The T/H circuit also provides additional scaling for certain ranges. ‘The Digital Controller controls the operation of virtually every part of the 8840A. It reads the front panel keyboard, configures the instrument for each function and range, triggers the A/D Converter, calculates the result of each AID conversion cycle, averages A/D samples, controls the Section 5 Theory of Operation display, and communicates with the IEEE-488 Imerface Option via the Guard Crossing circuit. The heart of the Digital Controller is the In-Guard Microcomputer (iC). ‘The Guard Crossing circuit permits serial asynchronous communication between the Digital Controller and the TEEE-488 Interface Option, while isolating the two circuits clectrically. Whereas the in-guard power supply floats with the voliage at the INPUT LO terminal, the IEEE-488 Imerface Option operates with reference to earth ground. The “guard” is the isolation between the in-guard and out-guard circuits. ‘The Power Supply provides supply voltages to all parts of, the instrument. The Precision Voltage Reference provides precise reference voltages for the A/D Converter and the ‘Ohms Current Source. §3. DETAILED CIRCUIT DESCRIPTION ‘The following paragraphs give a detailed circuit descrip- tion of each of the functional blocks in Figure 5-1. For clarity, measurement ranges are referred to as 11, 12, 13, ‘eic., where 11 is the lowest possible range, 12 the next higher range, and so on. Pins are designated by the respec- tive integrated circuit (e.g, U101-7 for U1O1 pin 7) 5-4. DC SCALING ‘The DC Scaling circuit scales all in-range de inputs so that the output of the Track/Hold (T/H) amplifier (U307) is within #2V. In addition, the DC Scaling circuit provides input protection and analog filtering. Additional scaling is Provided by the the T/H Amplifier. ‘The following paragraphs describe the configuration of the DC Scaling circuit in the DCV and mA DC functions and also describe the analog filter. The ohms functions are described under a later heading because the T/H Amplifier provides additional input switching for these functions. 5-5. VDC Scaling Scaling is performed in the VDC function by two preci sion resistors networks (2301 and Z302). These compo- S41‘Theory of Operation c'ScALING NIT waMOd! { NOudo ! sna gey-3331 ) 30vauaLNI | eor-a3at lonoee-t Adds waMOd 1 anant sevi70n0a_! nonao ov IOV 1 swu anus | peo 1 I ‘auvno-Ni Voupeeu STyNINUAL Anant =o lyaIOULNOo uaLUaANOO LuNouIO Linouto oe Twila aw Javon ovull* govi10n oa] ONMWVOS 00 [*—InaNt aawos @e 4NauUNO 1831 zounos ‘SN TWNUALNI ANBHUNO ‘SWHO RONaHaIaY BOVLION NoIsIOaud Figure 5-1. Overall Functional Block Diagram 52Theory of Operation DC SCALING: nents are configured by relay K301, switching transistor Q311, and quad analog switches U302A and U301B to provide the correct scaling for each range. Voltage fol- ower U306 provides high input impedance for the 20V dc ange. A simplified schematic and a switch state table for the VDC function are shown in Figure 5-2. In the 200 mV and and 2V ranges, the input voltage is applied directly to the T/H Amplifier via 0310, 0311, and ‘U3OIB. In the 200 mV range, the T/H Amplifier has a gain of 10; in all other de voltage ranges, the ‘T/H Ampli- fier 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. To allow 'U306 to handle =20V its power supplies are “boot- strapped” by Q305 and Q306, so that the output voltage of 'U306 determines the midpoint of its supply voltages. The 99M Lo! K301 SHOWN ENERGIZED SWITCH STATES FOR VDC To TRACK/HOLD —— SENSE PATH FOR ‘VDC, 200 mV RANGE RANGE | sto | k301 | 311 &| Us02a | U302D U301B 200 mv . . . NOTE wv . . . | 20v . . . ‘TABLES SHOW CONFIGURATION | 200v . . DURING TRACK PERIOD OF 1000V . . ‘TRACK/HOLD CYCLE. FILTER SWITCH Q304 IS ON SWITCH STATES FOR mA DC. FOR THE S READING RATE IN VDC. gai & RANGE | 310 | K301 | ‘Ugors | U302A | U302D 200 mA . 5 Switch closed (or relay energized). Figure 6-2. DC Scaling (VDC and mA DC) 53Theory of Operation Dc SCALING Positive supply is approximately 6.2V above the input and the negative supply is approximately 6.2V below. In the 200V and 1000V ranges, K301 is de-energized and the input voltage is divided by 100 by Z302. In the 200V ange, the reduced input voltage is then applied directly to the T/H Amplifier as in the 2V range. In the 1000V range, ‘the reduced input voltage is buffered by U306 and divided by 10 as in the 20V range. 5-6. VDC Protection Input protection for the VDC function is provided by a 1K, fusible resistor (R309), four metal-oxide varistors (MOVs) (RV301, RV402, RV403, and RV404), and additional Protection resistors and clamp circuits. WARNING TO AVOID INJURY OR EQUIPMENT DAMAGE, USE EXACT REPLACEMENT PARTS FOR ALL PROTECTION COM- PONENTS. In all dc voltage ranges, voltage transients greater than 1560V are clamped by the MOVs. Extreme overvoltage conditions cause R309 to fail open-circuit. R309 is followed either by a 99 kQ, 10W resistor network (Z304) in the 200 mV, 2V, and 20V ranges, or by 10 MO (2302) to ground in the 200V and 1000V ranges. 2304 provides current limiting in extreme overvoltage condi- tions in the 200 mV, 2V, and 20V ranges. The non- inverting input of U306 is clamped to 225V by Q307 and 0308. 5-7. mA DC Scaling In the mA DC function, the unknown current causes voltage drop across current shunt R319. This voltage drop is then measured as in the VDC function. The DC Scaling circuit is configured as shown by the simplified switch table in Figure 5-2. 5-8, Analog Fitter ‘The three-pole, low-pass analog filter (U304) has a Butter- worth response with comer frequency at 7 Hz, giving approximately 50 dB of rejection at SO Hz. The filter is used only for the slow reading rate and is used only in the VDC ranges and lowest three ohms ranges. The filter is ‘switched into the input signal path by Q304 (Figure 5-2) In some ranges and functions, additional filtering is pro- vided by U302B and C314. 5-9. TRACK/HOLD CIRCUIT The Track/Hold (T/t) circuit presents a stable voltage 10 the A/D Converter during the input period of the A/D 54 conversion cycle. The circuit also provides a gain of 10 in the 200 mV dc, 2002, and 2000 mA de ranges. ‘The T/H circuit consists of the T/H Amplifier (Figure 5-3), ‘T/Hl capacitor C308, quad analog switches U301, 302, ‘and U303, and associated components. As shown in Figure 5-3, the TH Amplifier functions as an op amp, with Q314 supplying additional gain. In subsequent figures, the T/H Amplifier is represented as a single op amp. ‘The circuit operates by cycling between the track, settling, hhold, and precharge configurations shown in Figure 5-4, ‘The In-Guard uC selects a particular settling and hold configuration for each function and range, and suppresses the precharge configuration for certain ranges. This control is achieved by latching function and range information in 1U301, U302, and U303. Basic timing for the T/H circuit is provided by the A/D Converter over clock lines PC, HD1, TRI, and TR2. (See the timing diagram in Figure 5-5, top.) The T/H cycle is initiated when the In-Guard uC pulls line TR low. 5-10. Track Configuration Jn the track configuration (Figure 5-4A), the T/H circuit functions as a non-inverting buffer. The voltage on C308 tracks the scaled de input voltage. 511. 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 config- uation 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. Hold Configuration ‘The X1 hold configuration (Figure 5-4D) is used for all VDC ranges except ri and for all ohms ranges except r1. ‘The output of U307 is the negative of the input voltage. The X10 hold configuration (Figure 5-4B) is used for the mA DC function, the 200 mV de range, and the 2002 range, and provides a gain of 10. 5-13. Pre-Charge Configuration ‘The pre-charge configuration (Figure 5-4F) occurs) after the hold configuration in VDC ranges rl, 12, and r4, and ‘ohms ranges 11, 12, 13, and r4. U306 is connected as a buffer to charge stray capacitance at the non-inverting input of the T/H Amplifier. The pre-charge configuration is not used in any other ranges. 5-14. PRECISION VOLTAGE REFERENCE ‘The Precision Voltage Reference (Figure 5-6) provides precise reference voltages of -7.00000 and +7.00000. Theof rection vl nae eRe +15 “sv Figure 5-3. Track/Hold Amplifier Teference element is a reference amplifier (ref amp). The ‘nominal ref amp voltage is 6.5V. Resistor R701, precision resistor network Z701, and tran- sistor/zener diode combination U701 ate 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. The gain of U702B is set by the two 20 kQ resistors in the resistor network 2702. 5-15, OHMS CURRENT SOURCE ‘The Ohms Current Source (Figure 5-7) provides a precise fest current for the ohms functions. The first stage (U401, R401, and Q401) produces a precise reference current, using precision resistor R401 and a -7.0000V reference voltage from the Precision Voltage Reference. ‘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 uC. ‘The In- Guard WC sets the output current for each range by con- trolling U402 and U403. (See switch state table in Figure 5-7) 5-16. OHMS PROTECTION ‘The Ohms Protection circuit (Q402, 0403, 0404, 04085, (0406, and 0407) clamps the open circuit voltage of the Ohms Current Source and provides protection for the Ohms Current Source. ‘The circuit protects the Ohms Current Source from up to #300V across the INPUT terminals. The circuit also clamps voltage transients larger than 1560V with four MOVs (RV401, RV402, RV403, and RV404). In addition, 2.1 KQ, 2W fusible wire-wound resistor (R410) in series with the output current path fails open-circuit ‘under extreme overvoltage conditions. 55‘Theory of tion ora PocrEcnon oP ‘TRACK CONFIGURATION ‘SETTLING CONFIGURATIONS A) 5) GAIN OF 1 ©) GAIN OF 10 Vw usorc' t ja03A cu 4 U808D 18K 908 SK Us088 v HOLD CONFIGURATIONS D) GAIN OF 1 E) GAIN OF 10 To TO Usorc, “0 une, A/D NOTE: IN 4-WIRE OHMS v v RANGES R1 THROUGH Ré, + INPUT OF THE T/H AMP 1S SWITCHED AS SHOWN. coe (USS caus | 158 sos 18k vine 3 uses Vv PRECHARGE CONFIGURATION F) (CAPACITANCE “SETTING 18K DEPENDS ‘ON RANGE 2K u3038 Figure 5-4. Track/Hold Circuit ConfigurationsTheory of ‘OHMS. ‘TRACK/HOLD CONTROL, SIGNALS HOLD i = i 4 H ' i g § E ® 8 sort ja--f= @ ©& & & e 2 A/D CONTROL, SIGNALS jowazoiny lauO1s-HaQNIVWaY [auvaWoo aUOLS-UaQNIVWal 12.5 ms| (NOT TO SCALE) TR | | | | NOTE 1. All times in sss unless otherwise indicated, —__________v FIVE MEASUREMENT INTERVALS TRE 8. For 60 Hz line frequency, line TR has 2. HD2= 125 ms period as shown above. Figure 5-5. Timing Diagram for One A/D Cycle 87‘Theory of Operatic ols Protecnon oP REF AMP SUPPLY +7 Figure 5-6. Precision Voltage Reference Large positive input voltages are blocked by CR402. Large negative input voltages are dropped equally actoss three high-voltage transistors (402, 0403, and Q404). If -300V is present at the collector of Q404, the voltage drops equally across Z402 so that large negative voltages never reach the current source. The circuitry associated with Q408 (R406, R407, R408, R409, 0406, Q408, and CR403) clamps the open-circuit voltage of the Ohms Current Source below +65V in the lower four ranges and below +13V dc in the higher two ranges. The in-guard wC turns Q408 on or off depending ‘on range. In the lower four ohms ranges, Q408 is on, effectively shorting R409; R406 and R409 then form a voltage divider which clamps the output of the ohms current source below +6.5V. In the higher two ohms anges, 0408 is off, including R409 in the voltage divider and clamping the output below +13V. 5-17. OHMS FUNCTIONS 5-18. 2-Wire Ohms In the 2-wire ohms function, the Ohms Current Source is ‘connected to the INPUT HI terminal by ohms relay K401 Figure 5-8). The Ohms Current Source applies a known current to the resistance under test, and the resulting 58 voltage drop across the resistor is measured (“sensed”) as in the VDC function. ‘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 four ranges, the full scale input voltage to the AID Converter is 2V. However, in the 2000 k@ and 20 ‘MG ranges, the full-scale input voltage to the A/D Con- verter is +1V; the in-guard wC completes the scaling by multiplying the A/D result by 2. 5-19. 4-Wire Ohms In the 4-wire ‘ohms function, the Ohms Current Source is ‘connected to the INPUT Hi terminal by ohms relay K401 as in 2-wire ohms (Figure 5-8). The Ohms Current Source applies a known current to the resistance under' test through the INPUT HI and INPUT LO leads. The resulting voltage drop across the resistor is measured by the SENSE Hi and SENSE LO leads. ‘The voltage at the SENSE HI terminal is connected to the DC Scaling circuit by Q303 (Figure 5-8). The voltage is then scaled exactly as in the 2-wire ohms function. (Refer to the track period in the switch table in Figure 5-8.) Q310Theory of Operatio Ory ores TONS REFERENCE CURRENT | ‘O.0v w FROM PRECISION VOLTAGE REFERENCE z401 TO OHMS | SWITCH STATE TABLE PROTECTION RANGE | 402A u4o2e | u4ozc| U4020 | u4osa | 4038 | U4oac | Usos0| TT — 2000 . eal | 2K . eile 20K . . ele 200k . . . . 200k2 | ele . 20Ma . . ‘© = Switch closed Figure 5-7. Ohms Current Source is tumed off to isolate the SENSE HI terminal from the INPUT HI terminal. Additional input switching occurs during the hold period Of the track/hold cycle. (Refer to the hold period in the switch table in Figure 5-8. In ranges +1 through 1, the SENSE LO terminal is switched into the dc input path by U3OLD, and the INPUT LO terminal is switched out of the dd input path by U3OIC. This has the effect of measuring the SENSE HI terminal with respect to the SENSE LO terminal In ranges 15 and 16, the SENSE LO and INPUT LO terminals are both switched into the de input path by U3OIC and U3OLD during the hold period. This has the effect of measuring the SENSE HI terminal with respect to INPUT LO terminal rather than SENSE LO. Although the resistance of the INPUT LO lead is in series with the ‘unknown resistance, accuracy is not affected as long as the resistance of the lead is less than 102 in the 2000 k2 Tange and less than 100 in the 20 MQ range. 5-20. A/D CONVERTER ‘The Analog-to-Digital (A/D) Converter (Figure 5-9) uses Fluke’s patented recirculating remainder technique. An input voltage (Vin) is compared to the output of the precision Digital-to-Analog Converter (DAC). The output of the A/D Amplifier, connected as a comparator, is 59Theory of Operation SENSE PATH FOR 2 WIRE OHMS, 2009 RANGE, DURING TRACK PERIOD. ¢ To HI ‘TRACK/HOLD OHMS |CURRENT 100K ‘SOURCE, ANALOG FILTER INPUT SENSE us01D Lo Loo —— 301 AND K401 SHOWN ENERGIZED | | PERIOD] RANGE aor | Q310 | a303 | Ks01 | a3tt | Uso1B u3010 TRACK | 2000 . 2 4 . . . 2K . 2 4 . . . 20 ka . 2 4 . . . 200 ka. . 2 4 . . . 2000 kA . 2 4 . . 20M. . 2 4 . ° HOLD | 2000 . 2 4 . . 2 4 | 2Ka . 2 4 . 2 4 | 20KQ . 2 4 . 2 4 200 ka. . 2 4 . 2 4 2000 kA . 2 4 . . . 20MQ . 2 4 ° . . ‘@ = Switch closed (or relay energized). ‘Switch closed only in 2 WIRE ohms. NOTE: Filter switch Q304 is for the ‘Switch closed only in 4 WIRE ohms. S reading rete, ranges r1. (2; and rp. Figure 5-8. Ohms ScalingTheory of Operation Yio CONVERTER ‘monitored to indicate when the DAC output is larger than ‘the input voltage. 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 fist compare period (shown in Figure 5-9), the AID Converter determines the value of the scaled input voltage (Vin) by comparing Vin to the output of the DAC. Each of the DAC bit-switches is tried in sequence and kept ‘or rejected (left closed or reopened) depending on the ‘output polarity of the A/D Amplifier, which is configured as a comparator. This process produces a string of six bits which is stored in the Timing/Data Control circuit (the digital portion of U101).. ‘During the following remainder-store period (Figure 5-10), the difference between the Vin and the DAC output is ‘multiplied by 16 by the A/D Amplifier and stored on capacitor C102. During subsequent compare and emainder-store periods, the remainder voltage is con- nected to the input of U103 and is resolved to six bits; the remainder voltage (multiplied by 16) is stored altemately ‘on capacitor C102 and C103. Each of the five compare ppetiods thus produces a six-bit nibble which is stored in the Timing/Data Control circuit. This five-interval process thus generates five nibbles which are processed by the In-Guard uC to produce one AMD sample. After the fifth nibble is generated, U101 interrupts the In-Guard uC over line INT. The In-Guard uC then pulls line CS7 low five times, causing U101 to send the UC the five (six-bit) nibbles one-at-a-time over lines ADO-ADS. The In-Guard uC then weights each nibble 1/16 of the value of the previous number and calculates the input voltage. ‘The hardware for the A/D Converter has four major sec- tions: Timing/Data Control, Precision DAC, A/D Ampli- fier, and bootstrap supplies. 5-21. Timing/Data Control ‘The Timing/Data Control circuit (the digital portion of ‘U101) times and controls the A/D Converter by manipulat- ing the switches in the A/D Amplifier and the bit-switches in the Precision DAC. An A/D conversion cycle is trig- gered by the falling edge of line TR from the In-Guard HC. Once triggered, the A/D Converter (under control by U101) generates the five 6-bit nibbles without further interaction with the In-Guard uC. ‘The Timing/Data Control circuit also provides a watch- dog timer (line RES) which resets the In-Guard wC in case normal program execution is interrupted. If the timer | BINARY LADDER NETWORK DAC AMPLIFIER ‘AID AMPLIFIER, cr NO a NOTE: A/D CONVERTER SHOWN DURING FIRST COMPARE PERIOD. Figure 5-9. Analog-to-Digital Converter satTl Operatior memxstgemton Dac BIT SWITCHES SET DURING PREVIOUS COMPARE PERIOD AID AMP (x16) STORAGE c ae 10, Figure 5-10. First Remainder-Store Period senses inactivity on line CS7 for longer than 1.5 seconds, it resets the In-Guard uC by pulling RES low. ‘The Timing/Data Control circuit is supplied with a fixed- rate 8 MHz clock and provides a 1 MHz output clock for the Keyboard/Display Interface (U212). In addition, four output lines (PC, HDi, TR1, and TR2) provide contro! signals for the Track/Hold circuit. 5-22. Precision DAC ‘The Precision Digital-to-Analog Converter (DAC) is com- posed of DAC Amplifier U102B and a binary ladder network, which consists of resistors in Z101 and digitally controlled analog bit-switches contained in U101. ‘The bit-switches determine the output voltage of U102B by controlling the binary ladder network. The gain of ‘ULO2B 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 remainder-storage capacitors (C103 and C102), an autozero storage capacitor (C101), and several digitally controlled analog switches contained in U101. S12 ‘The A/D Amplifier has three modes of operation: autozero mode, where any offsets in the A/D input are stored on C101 so as to be cancelled later; compare mode, where the ADD input is compared to the DAC output; and remainder- store mode, where U103 amplifies and stores the differ- ‘ence between the A/D input and the DAC output on one of the two remainder-storage capacitors (C102 or C103). The ‘autozero mode is shown in Figure 5-11. The other modes aze shown in Figures 5-9 and 5-10. 5-24, Bootstrap Supplies The supplies are composed of U102A, Q101, Qi02, CR103, CR104, and associated components. The bootstrap supplies enhance the gain accuracy of U103. During compare periods, the bootstrap supplies limit the output of U103 to minimize the time it takes to recover from being driven to a supply rail. Both functions are achieved by manipulating the supplies of U103 (BS1. and BS2). 5-25. DISPLAY ‘The vacuum fluorescent display is similar to 2 vacuum tube, containing eight control grids and 69 phosphor- ‘coated plates which form the display segments and annun- ciators. (See Figure 5-12.) The filament voltage is 4.5V ac, with @ 45V de bias. Each plate is controlled by a G lineTheory of Operation DISPLAY PRECISION DAC | | 10.667K C101 ‘A/D AMPLIFIER, Figure 5-11. Autozero Period and a P line. The G lines go to the control grids, and the P lines go to the plates. ‘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 (ie., raised to a nominal +30V de by the igital Controller), the electrons continue past the grid and strike the respective plate, causing it to glow. 5-26. KEYBOARD The keyboard consists of a silicone-rubber switch matrix located over metalized epoxy contacts on the printed wire Figure 5-12. Vacuum Fluorescent Display board. Each button contains a conductive pad that shorts two contacts wien pressed, §-27. DIGITAL CONTROLLER ‘The Digital Controller (Figure 5-13) consists of the In- Guard wC (0202), External Program Memory (U222), Calibration Memory (U220), Keyboard-Display Interface, and associated components. 5-28. In-Guard Microcomputer ‘The In-Guard Microcomputer (uC) is a single-chip 28 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 1/0 lines. The In-Guard uC 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 2 100 kO resistor inside the uC. All internal bus communication is memory-mapped. Each ‘component that sends or receives data on the bus has a unique address or range of addresses. The internal bus consists of lines ADO-AD7 and A8-A11. Lines ADO-AD7 ‘are time-multiplexed to camry both the least-significant address byte and the data. Lines A8-A11 carry the most- significant bits of the address. The uC writes to and reads from the intemal bus according to the read and write cycles shown in Figure 5-14. During either cycle, the address strobe (AS) changes from low to high when an 513Theory of Operation DIGITAL CONTROLLER ‘11a SS3UOGV 153MO78 | seen nous Lines od = = waLuaanoo i ToT patevna [onal aounos = oe a ee ‘suinowo : ae ae [4 os ——s q J NOILdO- sovaiaiw KY owssovo | was z imac 1 wa | Joy's! TouINoa ar J frounnoo Aviat Figure 5-13. Digital Controller Block Diagram 614address is valid, and the data strobe (DS) changes from low to high when the data is valid. ‘The address strobe latches the address on ADO-ADT into U219 which then provides static address inputs for those devices that need it while data is on the bus. The data memory line (DM) divides the address space between rogram memory (U222) and data memory (all other devices on the bus). The data memory address space is further divided between the calibration memory (U220) ‘and the remaining devices by All. The addresses of the remaining devices ate decoded from A8-A10 by U208, which combines the address with the data strobe (DS) to provide a chip select (CSO, CS2, CS3, CS4, or CS7) for each device ‘The In-Guard 4C performs the following functions: range and function control; A/D control and computation; cali- bration corrections; keyboard/display control; serial com- munication with the IEEE-488 Interface; and diagnostic self-testing and troubleshooting. 5-29. Function and Range Control ‘The In-Guard uC configures the DC Scaling circuit, the Track/Hold circuit, and the Ohms Current Source to pro- vide 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. The quad analog switches (U301, U302, U303, 'U402, and U403) latch the configuration codes and per- form any level-shifting needed to control their internal MOSFET switches. Some of the switches require dynamic timing signals from the custom A/D IC (U101); these signals are combined appropriately in the quad ‘analog switches with the configuration codes. 5-30. A/D Control and Computation ‘The In-Guard uC initiates each A/D sample by pulling line TR low. When the uC is reset, it senses the power line frequency on line FREQ REF. The uC then sets its internal timer so that the A/D sample rate is as shown in Table 5-1. The mumber of readings per second for the slow and medium rates are chosen to provide rejection of input signals that are at the line frequencies. ‘The custom A/D IC (U101) generates five 6-bit numbers after each trigger from the uC and then pulls INT low, telling the uC that data is ready. The uC reads the five ‘G-bit numbers over the bus (CS7 pulses low five times for five read cycles) and computes the value of the A/D sample using calibration constants. The wC averages the appropriate number of samples for one reading, which is then sent to the keyboard/display interface for display. For example, with @ 60-Hz power-line frequency, an exter- nally triggered reading in the slow reading rate would cause the uC to send 32 pulses on TR at an 80 Hz rate. ‘The 32 A/D samples would be calibrated and averaged by Ti ot Comat the uC and sent for display. With internal triggering, the AID runs continuously at 80 samples per second with a reading being sent to the display every 32 samples. 5-31. Calibration Correction ‘The calibration constants used by the In-Guard) uC in ‘computing each reading are stored in the EEROM (clec- ‘wonically erasable read-only memory) Calibration Memory (U220). The front panel CAL ENABLE switch protects the EEROM from accidental writes. 5-32. Keyboard/Display Control Keyboard/Display Controller U212 communicates with the In-Guard uC over the internal bus. During a uC write cycle, address line A0 tells U212 whether to consider data being sent by the uC as configuration commands or as display data. Display data is stored in the Keyboard/Dis- play Controller, which automatically scans the display. ‘The Keyboard/Display Controller selects one of eight grids using decoder U213 and buffer U215. The mumeric display data is decoded from BCD to 7-segment by decoder U216 and buffered by U217. Additional annunciator data is buffered by U218. ‘The Keyboard/Display Controller is reset by the uC when- ever the uC is reset, It receives a 1 MHz clock signal from the custom A/D IC (U101), which uses the ¢C 8 MHz crystal for its clock input. ‘The Keyboard/Display Controller scans the keyboard, sensing pressed buttons on lines RLO-RL7. It sends an interrupt to the UC via line KEYINT whenever 2 front panel button is pressed. The uC then reads the keycode from the Keyboard/Display Controller. (The status of the FRONT/REAR switch is sensed separately by line F/R SENSE.) 5-33. Troubleshooting Modes In addition to running the diagnostic self-tests, the In- Guard wC has a troubleshooting mode which aids in finding digital hardware problems. After the C is reset, it senses the relay control lines (U202-35 through U202-38) as inputs. If line U202-38 (TP205) is shorted to ground, the uC goes into the troubleshooting mode. (U201 pro- vides internal pull-up.) The troubleshooting mode is described in detail in the Maintenance section. 5-34, Guard-Crossing Communication ‘The In-Guard wC contains a UART (universal asyachro- nous receiver transmitter) which it uses to communicate across the guard to the IEEE~488 Interface. The transmis- sion speed is 62,500 bits per second, 5-35. GUARD CROSSING ‘The Guard Crossing consists of two identical circuit of which transmits data in one direction across the guard isolation between the Main Printed Circuit Assembly and the IEEE-488 Interface. One circuit is shown in Figure 5-15; the other circuit works identically. A portion of each circuit is contained in the IEEE-488 Interface. 515‘Theory of Operation ‘GUARD GROSSING External /O or Memory Read and Write Timing ‘za6s1 782 | ous | Ne. Symbol Parameter Min Max Notes*t 1 TaAAS) ‘Address Valid to AS t Delay 50 1.23 2 TAAS(A) FS 1 to Address Float Delay Bi 12.3 3 TAAS(DR) AS 1 to Read Data Required Valid 360 1234 4 TwAS FS Low Width 80 1.2.3 5 TaAADS) Address Float to BS 1 ° 1 6—TwDsR- (Read) Low Width 250: 12.3.4 7 TwDSW DS (Write) Low With 160 1.2.3.4 8 TaDSR(DR) DB | to Read Data Required Valid 200 12.34 9 TRDR(DS) —Read Data to BS 1 Hold Time ° 1 10 Tata) DS 1 to Address Active Delay ” 1.23 11 TaDS(AS) DB 1 to AS | Delay 7 1.23 12—TaR/W(AS)—RY/W Valid to AS 1 Delay- 507 23 13° TaDS(RW) DS | to B/W Not Valid oO 12.3 14 TADW(DSW) Write Data Valid to DS (Write) 1 Delay 0 123 15 TADSDW) —_BS 1 to Write Data Not Valid Delay 0 123 16 TAA(DR) Address Valid to Read Data Required Valid 410 1234 17 TéAS(OS) __AS 1 toDS | Delay 0 128 Notes: Pert Lot 5. All oming reference ute 2.0 V for 6 ogee" and 08 V for eg“ 2 Taming nombre given are for ume TC * Allene on saneeconcs 3. hese lek cyte tne depandet characte tabla 1 Timmnge are prliary and suet ehanee. 4, When ung extended memory timing 038 96. {Zilog and 28€ are tradomarts of Zilog, in. with whom Jonn Fluke Mig. Co, ne. snot associate, Reproduced by permission ©1883 Zilog, Inc. This materia shall not be reproduced without the wren content of Zi0g, Ine 516 Figure 5-14. Read/Write Timing Diagrams for internal BusTheory of 0} ‘GUARD CROSSING ‘Table 5-1. Sample Rates and Reading Rates POWER SLOW MEDIUM FAST UNE ‘Samples Samples Samples ‘Samples ‘Samples ‘Samples FREQUENCY | per Sec | per Reading | per See | per Reading | per sec | per Reading 50 Hz 66.67 2 66.67 4 100 1 60 He 80 82 80 4 +100 1 400 Hz 76.19 32 76.19 4 100 1 The circuit in Figure 5-15 has two stable states, corre- sponding to output high (+5V) and output low (OV). 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. If the output of A is high, the output of B is low, forcing the inverting input of A (and the non-inverting input of B) to ground, hence reinforcing the existing state. The situation is analogous if the output of A is low. A positive-going transition at the input causes a positive pulse at the non-inverting input of A, and a corresponding negative pulse at the inverting input of A. If the output is high to star with (with the non-inverting inpat of A raised 140 mV above its inverting input), these pulses reinforce the existing state (raising the non-inverting input and lowering the inverting input). If, however, the output is ow to start with, the positive pulse (which is greater than 140 mV) raises the non-inverting input of A above its inverting input, switching the output to the high state. The situation is analogous for a negative-going input transition, 5-36. POWER SUPPLY ‘The Power Supply provides the following in-guard out- Puls: #30V, #15V, -6.2V, +7.5V, +5V, -SV, and -8.2V de; and 4.5V ac. The Power Supply also provides a 16V ac cemter-tapped out-guard output. Input line voltage is directed to the primary transformer winding through fuse F601, the front panel POWER switch, and the rear panel LINE SET switches. Metal oxide varistor RV601 clamps line transients at) about 390V. The LINE SET switcies configure the Power Sup- ply to accept line power of 100, 120, 220, or 240V ac (10% with a maximum of 250V) at 50, 60, or 400 Hz. AC voltage for the +5V supply is rectified by CR601 and (CR602 and regulated by VR6O1. The +5V output supplies mostly logic circuits. The ac input to the +5V supply is sensed by the In-Guard uC (via R604, CR615, and U221-12, 13) to measure the line frequency. AC voltage for the +30V and -30V supplies is rectified by bridge network CR603, CR604, CR60S, and CR606 and regulated by VR602 and VR60S. The’ +30V and -30V outputs supply front-end buffer amp U306. In addition, the +30V output supplies the anodes of the vacuum fluores- cent display. Zener diode CR612 supplies -6.2V to the AID Converter clamps. ‘AC voltage for the +15V and -15V supplies is rectified by bridge network CR608, CR609, CR610, and CR611 and regulated by VR603 and VR604. The +15V and -15V supply analog circuitry throughout the 8840A. Zener diodes CR613 and CR614 supply +7.5V and -8.2V to the AD Converter, analog filter, and DC Scaling circuit. { MAIN PRINTED CIRCUIT ASSEMBLY eas C202 £203 tao, i yas i INPUT: ' ois Nr IEEE-488 INTERFACE. Figure 6-15. Guard Crossing Circuit S17Theory of Operation Power Suery Secondary T601-14,15,16 supplies the vacuum fluorescent display filament with 4.5V ac. The center tap is connected ‘0 the in-guard +5V supply in order to correctly bias the display. An isolated secondary supplies 16V ac to the power supply on the IEEE-488 Interface. Zener diode CR615 and SCR Q601 comprise a protective ‘crowbar circuit. If the line voltage exceeds the nominal value by approximately 30 percent or mote, CR615 con- ducts, tuming on Q601, shorting out the power transformer secondary and blowing the line fuse. In normal operation, these components have no effect. 5-97. IEEE-488 INTERFACE (OPTION -05) ‘The IEEE-488 Interface has five major parts, as shown in the block diagram in Figure 5-16. All components sre contained in a single printed circuit assembly (PCA). Reference designations are numbered in the 900 series. 5-38. Out-Guard Microcomputer ‘The Out-Guard Microcomputer (uC) (U901) communi- ‘cates with the IEEE-488 talker/listemer IC (U911) and the In-Guard uC (U202). ‘The Out-Guard uC is similar to the In-Guard 28 uC ‘except that it contains 8K bytes of ROM and 236 butes of RAM. For further description of the Z8 uC, refer to the heading “In-Guard Microcomputer” above. 5-99. Guard Crossing ‘The guard crossing circuit permits serial asynchronous ‘communication between U901 and U202 while isolating ‘the two electrically. One-half of the guard crossing circuit is contained on the Main PCA; the other half is on the IBEE~488 Interface PCA. Operation of the guard crossing circuit is described in an earlier heading. 5-40. Bus Interface Circuitry ‘The IEEE-488 bus protocol is handled by the ¢PD7210 TEEE-488 talkerfistener IC (U911). It is controlled by U901 2s a memory mapped peripheral through an 8-bit ata. bus. Bus transceivers U912 and U913 buffer U911 from the TEEE-488 bus. They provide the bus with the required output drive capability and receiver impedance. S41. Signal Conditioning ‘The SAMPLE COMPLETE and EXT TRIG signals (1903 and J904) are conditioned by U909. Diodes CR903, (R904, CRIOS, and CR9O6 and resistors R917 and R918 rovide protection from excessive voltages. Jumpers E902 ‘and £903 allow selection of the polarity of the EXT TRIG ] IN-GUARD uC u202 ‘TRANSFORMER T601 SAMPLE COMPLETE SIGNAL EXTERNAL, CONDITIONING TRIGGER ‘TIEEE-488 INTERFACE OPTION IEEE-498 TALKERY LISTENER Icust ‘AND BUS TRANS- CEIVERS Figure 5-16. IEEE~488 Interface Block DiagramTheory of Operation IEEE-488 INTERFACE (OPTION -05; signal. (A polarity selection procedure is given in the Maintenance section.) The 8840A is configured in the factory so that it is triggered on the falling edge of the EXT TRIG signal. 5-42, IEEE-488 Interface Power Supply ‘The IEEE-488 Interface power supply circuit provides the IEEE-488 Interface PCA with +5V. The circuit consists of rectifying diodes CR908 and CR909, filter capacitor C910, and voltage regulator VR901. Power comes from trans- former T60S on the Main PCA. U908 and associated circuitry resets the Out-Guard uC at power-up and follow- ing power-line voltage dropouts. 5-43, TRUE RMS AC (OPTION -09) ‘The True RMS AC circuit (Figure 5-17) performs two primary functions. First, it scales ac input voltages and ac Current sense voltages to a range of OV to 2V ac ms. Second, it converts the scaled ac voltages to an equivalent de voltage which is then directed to the A/D Converter via the Track/Hold Amplifier. The True RMS AC circuit is ‘immed for flat high-frequency response using a variable filter which is set by the High-Frequency AC Calibration procedure. ‘The following paragraphs describe how these functions are performed. Components are laid out.on a single printed circuit assembly (PCA). Component reference designators are numbered in the 800 series. 5-44. VAC Scaling AC voltage inputs are directed from the HI INPUT termi- nal to the True RMS AC PCA through protection resistor R309 on the Main PCA. In this way, voltage transients greater than 1560V are clamped by MOVs (RV301, RV402, RV403, and RV404) as in the VDC function. With the VAC function selected, K801 is closed. The ‘input voltage is thus applied to C801, which blocks de inputs. 'U807 and resistor network 2801 provide selectable attenu- ation and 1 MQ input impedance. In the upper two ranges, K802 is closed and Q806 is off, providing a gain of /500. In the lower three ranges, K802 is open and Q806 is on, shorting Z801-4 to ground; this configuration pro- vides a gain of -1/5. CR801 and CR802 provide protection by clamping the inverting input of U807 to approximately 20.6V. Q805 shifts logic levels to control Q806. UB0GA, USO6B, 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 ‘USO6A is not used, its non-inverting input is grounded by (Q804. When UB06B is not used, its non-inverting input is connected to the CURRENT SENSE line. 5-45. mA AC Scaling ‘The mA AC function uses the same current shunt and protection network which is used for dc current. In the mA AC function, Q802 switches the CURRENT SENSE line to the non-inverting input of USO6B, which provides a gain of 10. 5:46. Frequency Response Trimming ‘The frequency response is trimmed by software calibration using a digitally controlled one-pole low-pass filter (R832 and a combination of C826, C827, C828, and C829). The analog switches in U808 configure the four capacitors 10 select one of 16 possible RC constants. The input of the digitally controlied filter is buffered by voltage follower UBOLA. The individual gain stages are also provided with fixed frequency compensation. 5-47. True RMS AC-to-DC Conversion USOLB buffers the input to rms converter U802. U802 computes the rms value of the scaled input voltage 2s shown in Figure 5-18, Rather than explicitly squaring and averaging the input, U802 uses an implicit method in AAC INPUT. VOLTAGE (+800 FOR ra, 5) CURRENT 5 SENSE VARIABLE RMS. FILTER CONVERTER To TRACK! rucrens Lo» ae HOLD circum VAC: orma AC. Figure 5-17. True RMS AC Option Block Diagram 619which feedback is used to perform an equivalent analog output is further filtered by a three-pole postfilter com- ‘computation. prised of U809B and associated resistors and capacitors. ‘This output is then switched into the Track/Hold Amplifier ‘The filter averages the divider output signal. This filter of the de front end via U302 pins 15 and 14. The consists of U809A, C813, R815, and the intemal 25 kQ ‘Track/Hold Amplifier is set up for unity gain on all. ac resistor and op amp between pins 8 and 9 of U802. The ranges. FILTER Vour Figure §-18. True RMS AC-to-DC Converter 5-20atic awareness @Q en Fluke Corporation ‘Some semiconductors and custom IC's can be damaged by electrostatic discharge during handling. This notice explains how you can eo minimize the chances of destroying such devices Ells ms jo 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 3. DISCHARGE PERSONAL STATIC BEFORE HANDLING DEVICES. USE A HIGH RESIS- 1. MINIMIZE HANDLING TANCE GROUNDING WRIST STRAP. Y 2. KEEP PARTS IN ORIGINAL CONTAINERS UNTIL READY FOR USE. 4, HANDLE S.S. DEVICES BY THE BODY.5. USE STATIC SHIELDING CONTAINERS FOR, 8. WHEN REMOVING PLUG-IN ASSEMBLIES HANDLING AND TRANSPORT. 6. DO NOT SLIDE S.S. DEVICES OVER ANY SURFACE. 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. STATIC-FREE WORK STATION. ‘SUCKERS SHOULD BE USED. ONLY GROUNDED-TIP SOLDERING IRONS SHOULD BE USED. cS. 9. HANDLE S.S. DEVICES ONLY AT A | | | 10. ONLY ANTI-STATIC TYPE SOLDER- " 7. AVOID PLASTIC, VINYL AND STYROFOAM® IN WORK AREA. PORTIONS REPRINTED WITH PERMISSION FROM TEKTRONIX INC. AND GENERAL DYNAMICS, POMONA DIV. © Dow Chemica! 9i93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 8840A. The section includes a performance test, a calibra- tion procedure, troubleshooting information, and other general service information, ‘Test equipment recommended for the performance test and. calibration procedure is.listed in Table 6-1. If the recom- mended equipment is not available, equipment that meets the indicated minimum specifications may be substituted. 62. PERFORMANCE TEST This test compares the performance of the 8840A with the specifications given in Section 1. The test is recommended as an acceptance test when the instrument is first received, and as a verification test after performing the calibration Procedure. If the instrument does not meet the perfor- mance test, calibration or repair is needed. To ensure optimum performance, the test must be per- formed at an ambient temperature of 18°C to 28°C, with a relative humidity of less than 75%. Also, the 8840A should be allowed to warm up for one hour prior to beginning any test other than the self-test. 6-3. Diagnostic Self-Tests ‘The diagnostic self-tests check the analog and digital circuitry in the 8840A. There are 21 analog tests followed by in-guard program memory, calibration memory, and display tests. Out-guard program memory is tested when self-test is initiated by a remote command. Microcomputer RAM tests are done only at powerup. Section 6 Maintenance NOTE The inputs must be left open-circuited while the selftests are performed. Otherwise, the ‘8840 may indicate errors are present. Errors ‘may also be caused by inductive or capacitive pick-up from long test leads. If the FRONTIREAR switch is in the REAR Position, the 88404 skips tests 3 and 4. Also, if Option -09 is not installed, the 8840 skips tests 1, 2, and 3. To initiate the selftests, press the SRQ button for 3 seconds. The TEST annunciator will then light up, and the ‘8840 will run through the analog tests in sequence. Each test number is displayed for about 1 second. The instru- ment can be stopped in any of the test configurations by Pressing the SRQ button while the test number is dis- Played. Pressing any bution continues the tests. ‘After the last analog test is performed, all display seg- ments light up while the instrument performs the in-guard Program memory, calibration memory, and display tests ‘The instrument then assumes the power-up configuration: VDC, autorange, slow reading rate, offset off, local con- trol, If the 840A. detects an error during one of the tests, it isplays the ERROR annunciator and the test number for about 2-1/2 seconds, and then proceeds to the next test ‘The test number thus becomes an error cade. (Error codes are listed in Table 2-1, Section 2.) Passing all diagnostic selftests does not necessarily mean the 8840A is 100% functional. The test, for example, ‘cannot check the accuracy of the analog circuitry. If one ot more errors are displayed, the 8840A probably requires service 6-4. DC Voltage Test The following procedure may be used to verify the accuracy of the VDC function: 61Maintenance PERFORMANCE TEST Table 6-1. Recommended Test Equipment pera vanmuw sPecireamions RECOMMENDED MODEL BE Gaia | PREFERRED Fis SR Fike BK Voltage Range: 0-1000V de Voltage Accuracy: 10 ppm Absolute Linearity: 21.0 ppm ALTERNATIVE: (Must be used with Kelvin Varley Voltage Divider) Voltage Range: 0-1000V oc Voltage Accuracy: 20 ppm + 20 pom of range Fluke 3438 Kelvin-Varley Voltage Divider: Ratio Range: 0-1.0 Absolute Linearity: =1 ppm of input at dial setting Fluke 7208) Resistor Calibrator Resistance Accuracy: 0.005% Fluke 57008 or Fluke 5450A, ESI DBG2 DC Current Source ‘Accuracy: =0.025% Fluke 5700A or Fiuke 100B ‘Oscilloscope General purpose, 60 MHz, with 10 MQ probe Philips 3085 or 3355 Digital Mutimeter Voltage Accuracy: 0.01% in V de 1.0% for 1V in V ac @ 100 kHz Input Impedance: 10 MQ or greater in V de; 1MQ or greater in parallel with <100 pF in V ac Fluke 88404 (with Option -08) "AC Calibrator Fluke 5700A and Fiuke 5725A Minimum Required Accuracy (By Range) eee 4, 10, 100 mv? 4, 10, t00v oo0v? Range 20 He - 80 He + 005 1+ 005 12 + 005 30 He - 20 ke 02 + 10 02 + .002 04 + 004 20 itz - 50 ke 05 + 20 05 + .008 08 + 005 50 kHz - 100 kHz 05 + 20 05 + .005 Aso 1. =(%6 of setting + nV) 2. +/-(06 of setting + % of range) ‘AC Current Source Fluke 57008 or Fiuke 51008 Frequency Minimum Required Accuracy Range (All Ranges) 90 He - 1 kHz 207% + 1 mA) 1 kez + 5 kHz 2(.07% + 1 mA) X frequency in kHz ‘Shorting Bar Resistance: <1.5 m2 Pomona MDP-S-0 Construction: Soldered (not rivetted) inch Jumper = E-Z-Hook 204-6W-S or equivalent Gorional Test | 9070A, 9005A or Micro-System Troubleshooter, @000A-6048 Interface Pod: uipment 62Maintenance Test PERFORMANCE TEST |. Ensure the 8840A is on and has warmed up for at least T hour. 2. Select the VDC function, 3. Connect the DC Calibrator (see Table 6-1) to provide a voltage input to the HI and LO INPUT terminals, If using the Fluke 343A and the Kelvin-Varley Voltage Divider instead of the Fluke 5440A, connect the test leads as shown in Figure 6-1 4. For each step in Table 6-2, select the indicated range, set the DC Calibrator for the specified input, and verify that the displayed reading is within the limits shown for each reading rate. (For step A, connect a short across the HI and LO INPUT terminals and press OFFSET. The measurement in step C should be relative to this offset.) 5. Set the DC Calibrator to input negative voltages, and repeat steps C through G of Table 6-2. 6. With the unit is the 2V range, check the A/D linearity by setting the DC Calibrator for each step in Table 6- 9, while verifying the display reading 1s within the limit shown. Set the DC Calibrator for zero volts and disconnect if from the 8840. 6-5. AC Voltage Test (Option -09 Only) The following procedure may be used to verify the accuracy of the WAC function: Ensure the 8840A is on and warmed up for at least 1 hour. Select the VAC function and the slow (S) reading rate, Connect the AC Calibrator to provide 2 voltage input to the HI and LO INPUT terminals. (Low- and Mid-Frequency Test.) For each step in Table 6-3, select the indicated range, set the AC Calibrator for the specified input, and verify that the displayed reading is within the limits shown for each reading rate NOTE This procedure tests the extremes of each range. You may shorten the procedure by testing only the “quick test points" indicated in Table 6-3 with asterisks. (High-Frequency Test.) for cach step in Table 6-4, select the indicated range, set the AC Calibrator for the specified input, and’ verify that the displayed reading is within the limits shown for each reading rate. NOTE This procedure tests the extremes of each range. You may shorten the procedure by testing only the “quick test points” indicated in Table 6-4 with asterisks. DG CALIBRATOR SENSE (FLUKE 9408) i oureur got REVERSE THESE TASS eon NEGATIVE INPUT VOLTAGE 108840 | KELVIN-VARLEY VOLTAGE | BWvibeR FLUKE 7208), ©,1 | nour ogre ©0660 000 000 990+ CONNECTIONS ARE SHOWN FORPOSTIVE NUT VOLTAGES FO cata | | NOTE: THE KELVIN-VARLEY VOLTAGE DMIDER IS | NOT REQUIRED FOR INPUT VOLTAGES ABOVE 20V DC. Figure 6-1. Connections for Kelvin-Varley Voltage Divider 63Maintenance PERFORMANCE TEST Table 6-2. DC Voltage Test DISPLAYED READING INPUT STEP| RANGE} Oy a0) SLOW ‘MEDIUM FAST? winmum | Maximum | MINIMUM | MAXIMUM | MINIMUM | MAXIMUM A* | 200 my [ov (shor) 00.003 ++00.003 -00.005) +00.005, -00.02 +00.02. B | 2V, 2ov./ov (shor) -3 counts | +3 counts | -5 counts | 45 counts | -2 counts | +2 counts 200v, ‘1000v C* | 200 mv {100 mv | 499.989 +100011 | +99.987 4100013 | 499.97 +100.03, D0 la v +.99993 +1.00007 | +.99901 +1,00009 | +9997 +4,0003, 1& lav |tov 49.9992 +1.00008 | +9.9990 #100010 | +9997 +10.003, F {200v_ | t00v 499.992 +100.008 | +99.990 +100.010 | 499.97 +100.03, & |ro00v |1000v | +999.02 +1000.08 | +999.90 +1000.10 | +990.7 +1003, NOTES: 6. Set the AC calibrator to standby and disconnect it from the $8404. 66. Resistance Test The following procedure may be used to verify the accuracy of the 2-wire and 4-wire ohms functions. 1. Ensure the 88404 is on and has warmed up for at least 1. hour. 2. Connect the Resistance Calibrator to the 8840A for 4-wire ohms. 1. Relative to high-quality shor stored using OFFSET feature. 2. When in fast reading rate with intemal tigger and transmiting data out of the IEEE-488 interface, the 8840A cfsplay ust be bianked (command D1) to ensure stated accuracy. | 3. For each step in Table 6-5, select the indicated range, set the Resistance Calibrator for the specified nominal ‘input, and proceed as follows: a. Test the 4-wire ohms function: 1. Select the 4-wire ohms function. 2. Verify that the displayed reading is within the limits shown for each reading rate. b. Test the 2-wire ohms function: 1. Select the 2-wire ohms function. (The SENSE test leads need not be disconnected.) Table 6-3. Low- and Mid-Frequency AC Voltage Test wap WeUT ERROR | TEST MTS QW VOLTS) wowper | "NSE | vourace | eRequency | oolirg | miNMuM wanum, 7 pa Go1000v 700 20H 00786 001201 2 | wv 0.10000 100 He 114 0.00888 10114 s av 0.30000V 100 Hz. 142 0.29858 0.30142 a law 1.00000 100 He 240 0.99760 1.00240 | sia 1.90000” 400 He 268 1.20634 1.90366 | 6 | aw 0.10000 20 Hz 220 0.03780 10220 | 7 |» 1.20000 20 He zaso | 187620 1.82380 8 law 10000” 15 He 135 086s 0.10196 os [aw 1.900007 45 He 785 4.80088 1.90765 10° 200 mv 0.001000V_ 100 Hz 201 0.000799 0.001207 11 | 200mv | or90000v 20 ke 368 0.189684 0.190966 “Quick test points. esMaintenance PERFORMANCE TEST Table 6-4. High-Frequency AC Voltage Test — INPUT ERROR TEST LIMITS (IN VOLTS) RANGE IN NUMBER VOLTAGE FREQUENCY | counts ‘MINIMUM MAXIMUM 1 200 mV | o.0T0000v 50 kHz, 169 0.009831 0.010169 a 200 mV 0.010000v 100 kHz 360 0.009650 0.010350 s av 0.10000v 100 kHe 360 0.09650 0.10350 a 20v 1.0000v 100 kt 360 0.9650 1.0350 s 200v 10.000V 100 kHe 350 9.650 10.350 e 700v 100.00 100 kHz 350 96.50 103.50 7 20v 19.0000V 100 kHe 1250 18.8750 19.1250 8 200 mv 0.180000V 100 kHe 1250 0.188750 0.191250 “Quick test points 2. Zero the test Jead resistance by pressing the 1. OFFSET switch while shorting the HI and LO INPUT test leads together. 2. Verify that the displayed reading is. within the limits shown for each reading rate, . 4 6-7. DC Current Test The following procedure may be used to test the mA DC Ensure the 8840A is on and has warmed up for at least 1 hour. Select the mA DC function. Connect the Current Source to the 2 and LO INPUT terminals. For each step in Table 6-6, set the Current Source for the indicated input and verify that the displayed read- function: ing is within the limits shown for each reading rate. Table 6-5. Resistance Test ERROR FROM INPUT STEP RANGE INPUT (Qn Counts)*

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