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Fluke 8842a instruction manual DC Scaling

Models: 8842a

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Theory of Operation 5

DC SCALING

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Figure 5-1. Overall Functional Block Diagram

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Fluke 8842a instruction manual DC Scaling

Contents

8842A Page Table of Contents 8842A Remote ProgrammingMeasurement 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 Introduction Options and Accessories8842A Digital Multimeter Specifications Peak NM Signal RateFilter True RMS AC Voltage Option 8842A-09Frequency Fundamental FrequencyCrest Factor For InputsFull Scale 5½ Digits Current½ Digits Range Full Scale Resolution Current ½ Digits Through UnknownHours 23±1C Rate Power Line FREQUECNCY1 Automatic Settling Time DelayAutoranging FunctionExternal Trigger Timing Characteristics Conversion Time ms 50 Hz 60 Hz 400 HzPower GeneralOperating Instructions Installing the Power-Line Fuse InstallationConnecting to Line Power Adjusting the Handle Rack Mounting KitsPower-Up Features Operating FeaturesFront and Rear Panel Features Operating Features Local button causes the 8842A to display its Rear Panel Features Display Features Error MessagesError Code Meaning Error CodeDiagnostic Self-Tests Overrange IndicationRanging AutorangeContinuous Trigger Mode External Trigger ModeManual Range TriggeringExternal Trigger Input Option -05 Only Automatic Settling Time DelaySample Complete Output Option -05 Only Making Measurements Input Overload Protection LimitsMeasuring Voltage and Resistance Measuring CurrentOffset Measurements External Cleaning Measuring Voltage and Resistance8842A Remote Programming Measurement Data Overrange Indication Error Messages BUS SET-UP Procedure CapabilitiesAN Overview of Remote Operation IEEE-488 Address SelectionAN Overview of Remote Operation DEVICE-DEPENDENT Command SET ExampleExplanationDEVICE-DEPENDENT Command SET Device-Dependent Command Set Cn Calibration Commands Bn Offset CommandsDn Display Commands Fn Function Commands Get CommandsCommand Output String Meaning13. G1 Get SRQ Mask 12. G0 Get Instrument Configuration14. G2 Get Calibration Prompt 15. G3 Get User-Defined Message 16. G4 Get Calibration Status17. G5 Get IAB Status 19. G7 Get Error Status18. G6 Get YW Status Numeric Entry Command Put Commands23. P0 Put Instrument Configuration 20. G8 Get Instrument Identification24. P1 Put SRQ Mask 25. P2 Put Calibration ValueSn Reading Rate Commands Rn Range Commands26. P3 Put User-Defined Message Tn Trigger Mode Commands Trigger Selection Logic DiagramWn Terminator Commands 31. X0 Clear Error Register CommandYn Suffix Commands 33. Z0 Self-Test Command35. ? Single-Trigger Command Device-Clear CommandInput Syntax Definitions Input ProcessingDEVICE-DEPENDENT Messages ERROR-PRODUCING CharactersInterface Messages Syntax Rules Incorrect exampleOutput Data Loading Output DataNumeric Data and Error Messages Overrange Indication Error MessagesTypes of Output Data Measurement DataError Messages Overrange IndicationStatus Data Output PriorityService Requests Serial Poll RegisterSRQ Mask SetInterface Messages Universal CommandsAddress Messages TALK-ONLY Mode Addressed CommandsRemote Calibration Immediate Mode CommandsTiming Considerations Immediate-Mode Commands for Various Controllers Example ProgramsExample 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 MeasurementInput Bias Current Error Measuring Input Bias Current ErrorWire Ohms Resistance MeasurementCorrecting for Test Lead Resistance in 2-Wire Ohms Test Current Full Scale VoltageTesting Electrolytic Capacitors Testing DiodesApplications of the Ohms Functions DC Current Measurement Precision Current SourceBurden Voltage Error Calculation Reducing Thermal VoltagesTrue RMS Measurement AC Voltage and Current MeasurementWaveform Comparison AC Voltage and Current Measurement Crest Factor AC-Coupled AC MeasurementsCombined AC and DC Measurements Zero-Input VAC ErrorBandwidth Reduction of Zero-Input Error 20Ω RangesMaking Accurate HIGH-RESISTANCE Measurements 10. Shielding for Low Voltage Measurements12. 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 ScalingDC Scaling VDC Scaling DC Scaling VDC and mA DCMA DC Scaling VDC ProtectionAnalog Filter TRACK/HOLD Circuit Track/Hold AmplifierTRACK/HOLD Circuit Track Configuration Timing Diagram for One A/D CycleSettling Configuration Hold ConfigurationPre-Charge Configuration Precision Voltage ReferenceOhms Current Source Ohms Current SourceOhms Protection Ohms FunctionsOhms Scaling 20. A/D Converter Analog-to-Digital Converter Timing/Data Control Precision DACDisplay Bootstrap Supplies23. A/D Amplifier Keyboard Digital Controller13. Digital Controller Block Diagram In-Guard Microcomputer 14. Read/Write Timing Diagrams for Internal Bus Slow Medium Fast Power Line Frequency Function and Range Control30. A/D Control and Computation Calibration CorrectionTroubleshooting Modes Guard CrossingKeyboard/Display Control Guard-Crossing CommunicationPower Supply IEEE-488 Interface Option Out-Guard MicrocomputerGuard Crossing Bus Interface CircuitryIEEE-488 Interface Power Supply Signal ConditioningVAC Scaling Frequency Response Trimming MA AC ScalingTrue RMS AC-to-DC Conversion Static awareness Dow Chemical Maintenance External Trigger Polarity Selection Option -05 Only Minimum Specifications Recommended Model Instrument TypePerformance Test Frequency Range Minimum Required Accuracy All RangesDC Voltage Test Step Range Input Slow Medium Fast MIN MAXAC Voltage Test Option -09 Only Voltage FrequencyResistance Test New Offset must be stored for each new range selectedDC Current Test Displayed ReadingSlow Medium MIN MAX Fast MIN MAXCalibration AC Current Test Option -09 OnlyStep Number Range Input Current FrequencyBasic Calibration Procedure Initial Procedure12. A/D Calibration Calibration FunctionsStep Displayed Prompt L O W a B L E ErrorStep Input Step Offset and Gain CalibrationDisplayed Prompt VDC VAC1 HIGH-FREQUENCY AC Calibration Storing Variable Inputs Advanced Features and Special ConsiderationsStep Displayed PROMPT1,2 Calibrating Individual Ranges Procedure Function LOW Prompt High PromptVerifying Calibration Erasing Calibration Memory Tolerance CheckAC Calibration AT Other Frequencies Optimizing USE of the 5450ACalibration ToleranceRemote Calibration Optimizing Use of the 5450ACorresponding Command Front Panel FeatureComments 8842A Timing Considerations Remote Erasure Example Calibration ProgramDisassembly Procedure Example A/D Calibration ProgramA Disassembly Case RemovalF6-062.wmf F6-063.wmf F6-064.wmf IEEE-488 Interface PCA Removal Option -05 Only True RMS AC PCA Removal Option -09 OnlyMain PCA Removal Maintenance Reassembly Procedure Front Panel DisassemblyReassembly Procedure Front Panel Disassembly Removing the Display Window Troubleshooting Internal Fuse ReplacementInitial Troubleshooting Procedure Troubleshooting 16. Overall State Table T6-162.wmf 17. Circuitry Tested by the Analog Self-Tests Diagnostic Self-Tests Test Number Self-Test DescriptionsTest Point Voltage Maintenance 8842A Digital Controller Troubleshooting IN-GUARD Microcomputer SystemIn-Guard Microcomputer Address Latch U219 Calibration Memory U220 Display SystemDisplay Control U212 To-8 Strobe Decoder U213 Analog Control Signals Evaluating Static Signals Device REF. DES21. Analog Control Logic States Evaluating Dynamic Signals DC Scaling TroubleshootingPIN or Device Supply VoltageTrack/Hold Troubleshooting Ohms Current Source Troubleshooting13. Typical Output Waveforms for Track/Hold Circuit TP103 Precision Voltage Reference Troubleshooting 66. A/D Converter Troubleshooting 14. Output of A/D Amplifier TP10115. Waveforms at U101-24 and U101-25 Power Supply Troubleshooting For fire protection, use exact fuse replacement only17. Waveforms at TP102 for Several Inputs on 2V DV Range Test Point Minimum MaximumService Position IEEE-488 Interface Troubleshooting OptionDiagnostic Program Troubleshooting Switches ConfigurationTrue RMS AC Troubleshooting Option Port BITDefective Ranges Major ProblemsDefective Stage Voltage AT TP801 Input VoltageVoltage AT TP802 More Obscure Problems Guard Crossing Troubleshooting Internal CleaningCleaning Printed Circuit Assemblies Cleaning After Soldering 21. Guard Crossing Test Waveforms8842A List of Replaceable Parts 8842A HOW to Obtain Parts Manual Status InformationService Centers Newer InstrumentsREF of Option no Assembly Fluke Part 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 Description ModelNumber Option Accessories Current Probes Y8100, Y8101, 80i-400 Current Shunt 80J-10High Voltage Probes 80K-6 and 80K-40 8842A Option -05 IEEE-488 Interface 805-2 External Controls Programming Instructions MaintenanceList 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