Display Control U212 | Fluke 8842a instruction

Maintenance 6

TROUBLESHOOTING

possible to freeze the display, it should still be possible to observe the waveforms at U215, U213, U221, and U211 as described in the following paragraphs.

To freeze the display, turn off the instrument, press the POWER switch and within 1 second press the SRQ button. If all is well, all display segments will light and remain lit. Do not press any other buttons as that will release the display, allowing the instrument to resume its normal power-up sequence. This state should remain in effect for all of the following tests.

f6-11.wmf

Figure 6-11. Waveforms for Display Logic

6-49. Display Control (U212)

Check for the 1 MHz clock from the A/D IC at U212-3.

NOTE

The following waveforms are illustrated in Figure 6-11.

6-50. 8-Bit Digit Driver (U215)

Check for strobe waveforms 0-7 on U215-8, -1. Reference U215-8 for waveform STROBE ZERO. U215-7 is STROBE ONE, U215-6 is STROBE TWO etc. High level is 3.8V to 4.3V and low is near 0V.

6-49

Image 186

Fluke 8842a instruction manual Display Control U212

Contents

8842A Page Table of Contents 8842A Remote Programming Measurement Tutorial Maintenance List of Replaceable Parts Schematic Diagrams List of Tables 805-7 List of Figures 805-8 IEEE-488 Interface PCA, Option True RMS AC PCA, Option Xii Introduction and Specifications Options and Accessories Introduction8842A Digital Multimeter Specifications Filter Peak NM SignalRate True RMS AC Voltage Option 8842A-09 Crest Factor FrequencyFundamental Frequency For Inputs Current Full Scale 5½ Digits½ Digits Range Full Scale Resolution Current ½ Digits Through Unknown Hours 23±1C Autoranging Rate Power Line FREQUECNCY1Automatic Settling Time Delay Function External Trigger Timing Characteristics Conversion Time ms 50 Hz 60 Hz 400 Hz Power General Operating Instructions Installation Installing the Power-Line FuseConnecting to Line Power Adjusting the Handle Rack Mounting Kits Operating Features Power-Up FeaturesFront and Rear Panel Features Operating Features Local button causes the 8842A to display its Rear Panel Features Display Features Error Messages Error Code Meaning Error Code Ranging Diagnostic Self-TestsOverrange Indication Autorange Manual Range Continuous Trigger ModeExternal Trigger Mode Triggering Automatic Settling Time Delay External Trigger Input Option -05 OnlySample Complete Output Option -05 Only Measuring Voltage and Resistance Making MeasurementsInput Overload Protection Limits Measuring Current Offset Measurements External Cleaning Measuring Voltage and Resistance 8842A Remote Programming Measurement Data Overrange Indication Error Messages BUS SET-UP Procedure Capabilities AN Overview of Remote Operation IEEE-488 Address Selection AN Overview of Remote Operation DEVICE-DEPENDENT Command SET ExampleExplanation DEVICE-DEPENDENT Command SET Device-Dependent Command Set Bn Offset Commands Cn Calibration CommandsDn Display Commands Fn Function Commands Get Commands Command Output String Meaning 12. G0 Get Instrument Configuration 13. G1 Get SRQ Mask14. G2 Get Calibration Prompt 15. G3 Get User-Defined Message 16. G4 Get Calibration Status 19. G7 Get Error Status 17. G5 Get IAB Status18. G6 Get YW Status 23. P0 Put Instrument Configuration Numeric Entry CommandPut Commands 20. G8 Get Instrument Identification 24. P1 Put SRQ Mask 25. P2 Put Calibration Value Rn Range Commands Sn Reading Rate Commands26. P3 Put User-Defined Message Tn Trigger Mode Commands Trigger Selection Logic Diagram Yn Suffix Commands Wn Terminator Commands31. X0 Clear Error Register Command 33. Z0 Self-Test Command Device-Clear Command 35. ? Single-Trigger CommandInput Syntax Definitions Input Processing ERROR-PRODUCING Characters DEVICE-DEPENDENT MessagesInterface Messages Syntax Rules Incorrect example Output Data Loading Output Data Types of Output Data Numeric Data and Error MessagesOverrange Indication Error Messages Measurement Data Status Data Error MessagesOverrange Indication Output Priority Service Requests Serial Poll Register SRQ Mask Set Universal Commands Interface MessagesAddress Messages TALK-ONLY Mode Addressed Commands Immediate Mode Commands Remote CalibrationTiming Considerations Immediate-Mode Commands for Various Controllers Example Programs Example Programs 10. Example Program Taking Readings with Local Control 11. Example Program Using the Serial Poll Register 12. Example Program Record Errors During Selftest 13. Example Programs Using the IBM PC 14. Example Programs Using the IBM PC F3-1402.wmf F3-1403.wmf F3-1404.wmf F3-1405.wmf F3-1406.wmf F3-1407.wmf F3-1408.wmf F3-1409.wmf F3-1410.wmf F3-1411.wmf ASCII/IEEE Std 488-1978 Bus Codes 8842A Measurement Tutorial Circuit Loading Error DC Voltage Measurement Input Bias Current Error Measuring Input Bias Current Error Wire Ohms Resistance Measurement Correcting for Test Lead Resistance in 2-Wire Ohms Test Current Full Scale Voltage Testing Diodes Testing Electrolytic CapacitorsApplications of the Ohms Functions DC Current Measurement Precision Current Source Burden Voltage Error Calculation Reducing Thermal Voltages AC Voltage and Current Measurement True RMS MeasurementWaveform Comparison AC Voltage and Current Measurement Crest Factor AC-Coupled AC Measurements Zero-Input VAC Error Combined AC and DC MeasurementsBandwidth Reduction of Zero-Input Error 20Ω Ranges Making Accurate HIGH-RESISTANCE Measurements 10. Shielding for Low Voltage Measurements 12. Leakage Resistance in High Resistance Measurement Theory of Operation True RMS AC Option VAC Scaling MA AC Scaling Overall Functional Description Detailed Circuit Description DC Scaling DC Scaling VDC Scaling DC Scaling VDC and mA DC VDC Protection MA DC ScalingAnalog Filter TRACK/HOLD Circuit Track/Hold Amplifier TRACK/HOLD Circuit Track Configuration Timing Diagram for One A/D Cycle Pre-Charge Configuration Settling ConfigurationHold Configuration Precision Voltage Reference Ohms Current Source Ohms Current Source Ohms Protection Ohms Functions Ohms Scaling 20. A/D Converter Analog-to-Digital Converter Timing/Data Control Precision DAC Bootstrap Supplies Display23. A/D Amplifier Keyboard Digital Controller 13. Digital Controller Block Diagram In-Guard Microcomputer 14. Read/Write Timing Diagrams for Internal Bus 30. A/D Control and Computation Slow Medium Fast Power Line FrequencyFunction and Range Control Calibration Correction Keyboard/Display Control Troubleshooting ModesGuard Crossing Guard-Crossing Communication Power Supply Guard Crossing IEEE-488 Interface OptionOut-Guard Microcomputer Bus Interface Circuitry Signal Conditioning IEEE-488 Interface Power SupplyVAC Scaling MA AC Scaling Frequency Response TrimmingTrue RMS AC-to-DC Conversion Static awareness Dow Chemical Maintenance External Trigger Polarity Selection Option -05 Only Minimum Specifications Recommended Model Instrument Type Performance Test Frequency Range Minimum Required Accuracy All Ranges DC Voltage Test Step Range Input Slow Medium Fast MIN MAX AC Voltage Test Option -09 Only Voltage Frequency Resistance Test New Offset must be stored for each new range selected Slow Medium MIN MAX DC Current TestDisplayed Reading Fast MIN MAX Step Number Range CalibrationAC Current Test Option -09 Only Input Current Frequency Basic Calibration Procedure Initial Procedure 12. A/D Calibration Calibration Functions L O W a B L E Error Step Displayed PromptStep Input Offset and Gain Calibration StepDisplayed Prompt VDC VAC1 HIGH-FREQUENCY AC Calibration Advanced Features and Special Considerations Storing Variable InputsStep Displayed PROMPT1,2 Procedure Function LOW Prompt High Prompt Calibrating Individual RangesVerifying Calibration Erasing Calibration Memory Tolerance Check Calibration AC Calibration AT Other FrequenciesOptimizing USE of the 5450A Tolerance Remote Calibration Optimizing Use of the 5450A Front Panel Feature Corresponding CommandComments 8842A Timing Considerations Remote Erasure Example Calibration Program Disassembly Procedure Example A/D Calibration Program A Disassembly Case Removal F6-062.wmf F6-063.wmf F6-064.wmf True RMS AC PCA Removal Option -09 Only IEEE-488 Interface PCA Removal Option -05 OnlyMain PCA Removal Maintenance Reassembly Procedure Front Panel Disassembly Reassembly Procedure Front Panel Disassembly Removing the Display Window Internal Fuse Replacement TroubleshootingInitial Troubleshooting Procedure Troubleshooting 16. Overall State Table T6-162.wmf 17. Circuitry Tested by the Analog Self-Tests Diagnostic Self-Tests Self-Test Descriptions Test NumberTest Point Voltage Maintenance 8842A Digital Controller Troubleshooting IN-GUARD Microcomputer System In-Guard Microcomputer Address Latch U219 Calibration Memory U220 Display System Display Control U212 To-8 Strobe Decoder U213 Analog Control Signals Evaluating Static Signals Device REF. DES 21. Analog Control Logic States Evaluating Dynamic Signals DC Scaling Troubleshooting PIN or Device Supply Voltage Track/Hold Troubleshooting Ohms Current Source Troubleshooting 13. Typical Output Waveforms for Track/Hold Circuit TP103 Precision Voltage Reference Troubleshooting 66. A/D Converter Troubleshooting 14. Output of A/D Amplifier TP101 15. Waveforms at U101-24 and U101-25 Power Supply Troubleshooting For fire protection, use exact fuse replacement only 17. Waveforms at TP102 for Several Inputs on 2V DV Range Test Point Minimum Maximum IEEE-488 Interface Troubleshooting Option Service PositionDiagnostic Program Troubleshooting Switches Configuration True RMS AC Troubleshooting Option Port BIT Major Problems Defective RangesDefective Stage Input Voltage Voltage AT TP801Voltage AT TP802 More Obscure Problems Internal Cleaning Guard Crossing TroubleshootingCleaning Printed Circuit Assemblies Cleaning After Soldering 21. Guard Crossing Test Waveforms 8842A List of Replaceable Parts 8842A HOW to Obtain Parts Manual Status Information Service Centers Newer Instruments Assembly Fluke Part no REF of Option noRevision Level F7-011.wmf F7-012.wmf F7-013.wmf F7-014.wmf A1 Main PCA CABLE, Display HEADER,1 ROW,.156CTR,6 PIN 8842A F7-03.wmf A2 Display PCA F7-03.wmf Supply Codes for Manufacturers Supply2.wmf Service Centers Service2.wmf 8842A Options and Accessories 8842A Model DescriptionNumber Option Accessories Current Shunt 80J-10 Current Probes Y8100, Y8101, 80i-400High Voltage Probes 80K-6 and 80K-40 8842A Option -05 IEEE-488 Interface 805-2 External Controls Maintenance Programming InstructionsList of Replaceable Parts List of Replaceable Parts 805-6 805-7 805-8 Option -09 True RMS AC 809-2 Option -09 True RMS AC Operating Instructions 809-5 Option -09 True RMS AC PCA 809-7 809-8 Schematic Diagrams 8842A Schematic Diagrams F9-012.wmf Main PCA, A/D Converter F9-022.wmf Main PCA, Ohms Current Source F9-032.wmf Main PCA, Digital F9-042.wmf Main PCA, Power Supply F9-052.wmf Display PCA F9-062.wmf F9-071.wmf F9-072.wmf IEEE-488 Interface PCA, Option IEEE-488 Interface PCA, Option -08