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Fluke 8842a instruction manual VDC Scaling, DC Scaling VDC and mA DC

Models: 8842a

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8842A

Instruction Manual

5-5. VDC Scaling

Scaling is performed in the VDC function by two precision resistors networks (Z301 and Z302). These components are configured by relay K301, switching transistor Q311, and quad analog switches U302A and U301B to provide the correct scaling for each range.

Voltage follower U306 provides high input impedance for the 20V dc range. A simplified schematic and a switch state table for the VDC function are shown in Figure 5-2.

f5-02.wmf

Figure 5-2. DC Scaling (VDC and mA DC)

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Fluke 8842a instruction manual VDC Scaling, DC Scaling VDC and mA DC

Contents

8842A Page Table of Contents Remote Programming 8842AMeasurement 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 8842A Digital Multimeter Options and AccessoriesIntroduction Specifications Rate Peak NM SignalFilter True RMS AC Voltage Option 8842A-09Fundamental Frequency FrequencyCrest Factor For Inputs½ Digits CurrentFull Scale 5½ Digits Through Unknown Range Full Scale Resolution Current ½ DigitsHours 23±1C Automatic Settling Time Delay Rate Power Line FREQUECNCY1Autoranging FunctionConversion Time ms 50 Hz 60 Hz 400 Hz External Trigger Timing CharacteristicsGeneral PowerOperating Instructions Connecting to Line Power InstallationInstalling the Power-Line Fuse Rack Mounting Kits Adjusting the HandleFront and Rear Panel Features Operating FeaturesPower-Up Features Operating Features Local button causes the 8842A to display its Rear Panel Features Error Messages Display FeaturesMeaning Error Code Error CodeOverrange Indication Diagnostic Self-TestsRanging AutorangeExternal Trigger Mode Continuous Trigger ModeManual Range TriggeringSample Complete Output Option -05 Only Automatic Settling Time DelayExternal Trigger Input Option -05 Only Input Overload Protection Limits Making MeasurementsMeasuring Voltage and Resistance Measuring CurrentOffset Measurements Measuring Voltage and Resistance External Cleaning8842A Remote Programming Measurement Data Overrange Indication Error Messages Capabilities BUS SET-UP ProcedureIEEE-488 Address Selection AN Overview of Remote OperationAN Overview of Remote Operation ExampleExplanation DEVICE-DEPENDENT Command SETDEVICE-DEPENDENT Command SET Device-Dependent Command Set Dn Display Commands Bn Offset CommandsCn Calibration Commands Get Commands Fn Function CommandsMeaning Command Output String14. G2 Get Calibration Prompt 12. G0 Get Instrument Configuration13. G1 Get SRQ Mask 16. G4 Get Calibration Status 15. G3 Get User-Defined Message18. G6 Get YW Status 19. G7 Get Error Status17. G5 Get IAB Status Put Commands Numeric Entry Command23. P0 Put Instrument Configuration 20. G8 Get Instrument Identification25. P2 Put Calibration Value 24. P1 Put SRQ Mask26. P3 Put User-Defined Message Rn Range CommandsSn Reading Rate Commands Trigger Selection Logic Diagram Tn Trigger Mode Commands31. X0 Clear Error Register Command Wn Terminator CommandsYn Suffix Commands 33. Z0 Self-Test CommandInput Syntax Device-Clear Command35. ? Single-Trigger Command Input Processing DefinitionsInterface Messages ERROR-PRODUCING CharactersDEVICE-DEPENDENT Messages Incorrect example Syntax RulesLoading Output Data Output DataOverrange Indication Error Messages Numeric Data and Error MessagesTypes of Output Data Measurement DataOverrange Indication Error MessagesStatus Data Output PrioritySerial Poll Register Service RequestsSet SRQ MaskAddress Messages Universal CommandsInterface Messages Addressed Commands TALK-ONLY ModeTiming Considerations Immediate Mode CommandsRemote Calibration Example Programs Immediate-Mode Commands for Various ControllersExample 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 DC Voltage Measurement Circuit Loading ErrorMeasuring Input Bias Current Error Input Bias Current ErrorResistance Measurement Wire OhmsCorrecting for Test Lead Resistance in 2-Wire Ohms Full Scale Voltage Test CurrentApplications of the Ohms Functions Testing DiodesTesting Electrolytic Capacitors Precision Current Source DC Current MeasurementReducing Thermal Voltages Burden Voltage Error CalculationWaveform Comparison AC Voltage and Current MeasurementTrue RMS Measurement AC Voltage and Current Measurement AC-Coupled AC Measurements Crest FactorBandwidth Zero-Input VAC ErrorCombined AC and DC Measurements 20Ω Ranges Reduction of Zero-Input Error10. Shielding for Low Voltage Measurements Making Accurate HIGH-RESISTANCE Measurements12. Leakage Resistance in High Resistance Measurement Theory of Operation True RMS AC Option VAC Scaling MA AC Scaling Overall Functional Description DC Scaling Detailed Circuit DescriptionDC Scaling DC Scaling VDC and mA DC VDC ScalingAnalog Filter VDC ProtectionMA DC Scaling Track/Hold Amplifier TRACK/HOLD CircuitTRACK/HOLD Circuit Timing Diagram for One A/D Cycle Track ConfigurationHold Configuration Settling ConfigurationPre-Charge Configuration Precision Voltage ReferenceOhms Current Source Ohms Current SourceOhms Functions Ohms ProtectionOhms Scaling 20. A/D Converter Analog-to-Digital Converter Precision DAC Timing/Data Control23. A/D Amplifier Bootstrap SuppliesDisplay Digital Controller Keyboard13. Digital Controller Block Diagram In-Guard Microcomputer 14. Read/Write Timing Diagrams for Internal Bus Function and Range Control Slow Medium Fast Power Line Frequency30. A/D Control and Computation Calibration CorrectionGuard Crossing Troubleshooting ModesKeyboard/Display Control Guard-Crossing CommunicationPower Supply Out-Guard Microcomputer IEEE-488 Interface OptionGuard Crossing Bus Interface CircuitryVAC Scaling Signal ConditioningIEEE-488 Interface Power Supply True RMS AC-to-DC Conversion MA AC ScalingFrequency Response Trimming Static awareness Dow Chemical Maintenance External Trigger Polarity Selection Option -05 Only Instrument Type Minimum Specifications Recommended ModelFrequency Range Minimum Required Accuracy All Ranges Performance TestDC Voltage Test Slow Medium Fast MIN MAX Step Range InputVoltage Frequency AC Voltage Test Option -09 OnlyNew Offset must be stored for each new range selected Resistance TestDisplayed Reading DC Current TestSlow Medium MIN MAX Fast MIN MAXAC Current Test Option -09 Only CalibrationStep Number Range Input Current FrequencyInitial Procedure Basic Calibration ProcedureCalibration Functions 12. A/D CalibrationStep Input L O W a B L E ErrorStep Displayed Prompt Displayed Prompt VDC VAC1 Offset and Gain CalibrationStep HIGH-FREQUENCY AC Calibration Step Displayed PROMPT1,2 Advanced Features and Special ConsiderationsStoring Variable Inputs Verifying Calibration Procedure Function LOW Prompt High PromptCalibrating Individual Ranges Tolerance Check Erasing Calibration MemoryOptimizing USE of the 5450A AC Calibration AT Other FrequenciesCalibration ToleranceOptimizing Use of the 5450A Remote CalibrationComments Front Panel FeatureCorresponding Command 8842A Timing Considerations Example Calibration Program Remote ErasureExample A/D Calibration Program Disassembly ProcedureCase Removal A DisassemblyF6-062.wmf F6-063.wmf F6-064.wmf Main PCA Removal True RMS AC PCA Removal Option -09 OnlyIEEE-488 Interface PCA Removal Option -05 Only Maintenance Front Panel Disassembly Reassembly ProcedureReassembly Procedure Front Panel Disassembly Removing the Display Window Initial Troubleshooting Procedure Internal Fuse ReplacementTroubleshooting Troubleshooting 16. Overall State Table T6-162.wmf 17. Circuitry Tested by the Analog Self-Tests Diagnostic Self-Tests Test Point Voltage Self-Test DescriptionsTest Number Maintenance 8842A IN-GUARD Microcomputer System Digital Controller TroubleshootingIn-Guard Microcomputer Address Latch U219 Display System Calibration Memory U220Display Control U212 To-8 Strobe Decoder U213 Analog Control Signals Device REF. DES Evaluating Static Signals21. Analog Control Logic States DC Scaling Troubleshooting Evaluating Dynamic SignalsSupply Voltage PIN or DeviceOhms Current Source Troubleshooting Track/Hold Troubleshooting13. Typical Output Waveforms for Track/Hold Circuit TP103 Precision Voltage Reference Troubleshooting 14. Output of A/D Amplifier TP101 66. A/D Converter Troubleshooting15. Waveforms at U101-24 and U101-25 For fire protection, use exact fuse replacement only Power Supply Troubleshooting17. Waveforms at TP102 for Several Inputs on 2V DV Range Minimum Maximum Test PointDiagnostic Program IEEE-488 Interface Troubleshooting OptionService Position Switches Configuration TroubleshootingPort BIT True RMS AC Troubleshooting OptionDefective Stage Major ProblemsDefective Ranges Voltage AT TP802 Input VoltageVoltage AT TP801 More Obscure Problems Cleaning Printed Circuit Assemblies Internal CleaningGuard Crossing Troubleshooting 21. Guard Crossing Test Waveforms Cleaning After Soldering8842A List of Replaceable Parts 8842A Manual Status Information HOW to Obtain PartsNewer Instruments Service CentersRevision Level Assembly Fluke Part noREF of Option no 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 Number Option ModelDescription Accessories High Voltage Probes 80K-6 and 80K-40 Current Shunt 80J-10Current Probes Y8100, Y8101, 80i-400 8842A Option -05 IEEE-488 Interface 805-2 External Controls List of Replaceable Parts MaintenanceProgramming Instructions 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