FLUKE 78 电路图.pdf

78 Automotive Meter Service Manual For IEC 61010 CAT II Meters Only PN 666617 November 1998 1998 Fluke Corporation, All rights reserved. Printed in U.S.A. All product names are trademarks of their respective companies. RadioFans.CN 收音机爱 好者资料库 LIMITED WARRANTY a Caution identifies conditions and actions that might damage the meter. International electrical symbols used on the meter are shown below. W Warning To avoid possible electric shock or personal injury: Do not use the meter if it is damaged. Before use, inspect the case for cracks or missing plastic. Pay particular attention to the insulation surrounding the connectors. Always turn off power to the circuit before cutting, unsoldering, or breaking the circuit. Small amounts of current can be dangerous. Inspect the test leads for damaged insulation or exposed metal. Check test lead continuity. Replace damaged leads. To avoid damage or injury, never use the meter on unprotected circuits that exceed 4800 volt-amps. Do not use the meter if it operates abnormally. Protection may be impaired. When in doubt, have the meter serviced. Do not operate the meter around explosive gas, vapor or dust. Do not apply more than 300 V dc or ac rms (sine) between terminals or between any terminal and earth ground. Before each use, verify the meters operation by measuring a known voltage. When servicing the meter, use only specified replacement parts. Use caution when working above 30 V ac rms, 42 V ac peak, or 60 V dc. Such voltages pose a shock hazard. Keep your fingers behind the finger guards on the probe when making measurements. Connect the common test lead before connecting the live test lead. Disconnect the live test lead first. Remove test leads from the meter before opening the case. Use only a single 9 V battery, properly installed in the meter case, to power the meter. Follow all equipment safety procedures. Before measuring current, check the meters fuses (see “How to Test the Fuse”). Never touch the probe to a voltage source when the test leads are plugged into the 10 A input jack. RadioFans.CN 收音机爱 好者资料库 Always use clamp-on probes (dc current clamps) when measuring current exceeding 10 A. DO NOT connect thermocouple to voltages exceeding 30 V. Always use a high voltage probe to measure voltage if peak voltage might exceed 300 V. To avoid false readings, which could lead to possible electric shock or personal injury, replace the meters battery as soon as the low battery indicator (N) appears. To avoid fire hazard, only use a fuse identical in type, voltage rating, and current rating to that specified on the fuse rating label located on the case bottom. Do not operate the meter if it is disassembled. Always operate the meter with the case top and bottom properly assembled. Disassembly procedures and warnings are in the 78 Automotive Service Manual. Service procedures are for qualified personnel only. Caution To avoid possible damage to the meter or to equipment under test: Disconnect the power to the circuit under test and discharge all high voltage capacitors before testing resistance, continuity or diodes. Use the proper function and range for your measurement applications. When measuring current, turn off circuit power before connecting the meter in the circuit. Remember to place the meter in series with the current. Symbols SymbolMeaning Important information. See manual. Ground Fuse Double insulation (Protection Class II) Conforms to European Union directives i Table of Contents ChapterTitlePage 1Introduction and Specifications. 1-1 1-1.Introduction . 1-3 1-2.Organization of the Service Manual . 1-3 1-3.Conventions . 1-4 1-4.Specifications . 1-4 2Theory of Operation. 2-1 2-1.Introduction . 2-3 2-2.Functional Block Description . 2-3 2-3.Circuit Descriptions . 2-4 2-4.Input Overload Protection . 2-4 2-5.Rotary Knob Switch . 2-4 2-6.Input Signal Conditioning Circuits . 2-4 2-7.Volts Functions . 2-4 2-8.Ohms Function . 2-5 2-9.Continuity . 2-6 2-10.Temperature Function . 2-6 2-11.Diode Test Function . 2-7 2-12.RPM Function . 2-7 2-13.Current Function . 2-7 2-14.Analog Section of Integrated Multimeter IC (U1) . 2-7 2-15.Frequency Measurements . 2-9 2-16.Dwell and Duty Cycle Measurements . 2-9 2-17.Microcomputer Control . 2-9 2-18.Peripherals to U1 . 2-9 2-19.AC Buffer . 2-9 2-20.AC converter . 2-9 2-21.Active Filter . 2-9 2-22.A/D Converter . 2-9 2-23.Beeper . 2-10 2-24.Power Supply . 2-10 2-25.Display . 2-10 3Maintenance. 3-1 78 Service Manual ii 3-1.Introduction . 3-3 3-2.Recommended Equipment . 3-3 3-3.Operator Maintenance . 3-3 3-4.Case Disassembly . 3-3 3-5.Battery Replacement . 3-3 3-6.Fuse Test . 3-5 3-7.Fuse Replacement . 3-5 3-8.Circuit Assembly Removal . 3-5 3-9.Display Access . 3-5 3-10.Cleaning . 3-7 3-11.Performance Tests . 3-7 3-12.Setup . 3-7 3-13.Display Test . 3-8 3-14.DC Voltage Test . 3-8 3-15.AC Voltage Test . 3-9 3-16.Frequency Test . 3-9 3-17.Frequency, Dwell, and Duty Cycle Trigger Level Test . 3-10 3-18.RPM Test . 3-10 3-19.Ohms Test . 3-11 3-20.Continuity Test . 3-11 3-21.Diode Test . 3-12 3-22.DC and AC Current Test . 3-12 3-23.Temperature Test . 3-12 3-24.RPM80 Inductive Pickup Test (Optional Accessory) . 3-14 3-25.Calibration . 3-17 3-26.Troubleshooting . 3-18 3-27.Surface Mount Assemblies . 3-18 3-28.Power Supply Related Troubleshooting . 3-18 3-29.Common (Shunt) Regulator Troubleshooting . 3-19 3-30.Vdd (Series) Regulator Troubleshooting . 3-20 4List of Replaceable Parts . 4-1 4-1.Introduction . 4-3 4-2.How to Obtain Parts . 4-3 4-3.Manual Status Information . 4-3 4-4.Service Centers . 4-4 4-5.Parts Lists . 4-4 5Schematic Diagrams. 5-1 iii List of Tables TableTitlePage 1-1.Specifications. 1-5 2-1.Typical Voltage Levels and Tolerance (Referenced to Common). 2-10 3-1.Recommended Test Equipment. 3-4 3-2.DC Voltage Test. 3-8 3-3.AC Voltage Test. 3-9 3-4.Frequency Test. 3-9 3-5.Frequency, Dwell, and Duty Cycle Trigger Level Test . 3-10 3-6.RPM Test. 3-10 3-7.Resistance Test. 3-11 3-8.Continuity Test. 3-11 3-9.Diode Test. 3-12 3-10.DC and AC Current Test . 3-12 3-11.Functional Description of Power Supply Components. 3-19 3-12.Voltage Levels. 3-19 4-1.Fluke 78 Final Assembly. 4-5 4-2.A1 Main PCA. 4-7 5-1.Signal Abbreviations . 5-3 78 Service Manual iv v List of Figures FigureTitlePage 2-1.Block Diagram. 2-3 2-2.4 V Range Simplified Schematic. 2-5 2-3.400 Ohm Range Simplified Schematic . 2-6 2-4.A/D Converter . 2-8 3-1.Disassembled Fluke 78. 3-6 3-2.Display. 3-8 3-3.Ambient Temperature Lag Bath. 3-13 3-4.Setup for RPM80 Inductive Pickup Test. 3-15 3-5.Typical Waveforms for Inductive Pickup Test . 3-16 3-6.Calibration Adjustment Point. 3-17 4-1.Fluke Final Assembly. 4-6 5-1.A1 Main PCA. 5-5 78 Service Manual vi 1-1 Chapter 1 Introduction and Specifications TitlePage 1-1.Introduction. 1-3 1-2.Organization of the Service Manual . 1-3 1-3.Conventions. 1-4 1-4.Specifications. 1-4 78 Service Manual 1-2 Introduction and Specifications Introduction1 1-3 1-1. Introduction This Service Manual provides information on maintaining, troubleshooting, and repairing the Flu