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Automotive Meter
88
Service Manual
For IEC 61010 CAT II Meters Only
PN 666856 November 1998 Rev.1, 11/99
© 1998, 1999 Fluke Corporation. All rights reserved. Printed in U.S.A. All product names are trademarks of their respective companies.
LIMITED WARRANTY & LIMITATION OF LIABILITY Fluke Corporation (Fluke) warrants this product to be free from defects in material and workmanship under normal use and service for the life of the product. This warranty extends only to the original buyer or end-user customer of a Fluke authorized reseller, and does not apply to fuses, 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 on appropriate Fluke instruments 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. Fluke's warranty obligation is limited, at Fluke's option, to refund of the purchase price, or free of charge repair or replacement of a defective product which is returned to an authorized Fluke Service Center within the warranty period. To obtain warranty service, contact your nearest Fluke Service Center or send the product, with a description of the difficulty, postage and insurance prepaid (FCA Destination), to the nearest Fluke Service Center. Fluke assumes no risk for damage in transit. Following warranty repair, the product will be returned to Buyer, transportation prepaid (FCA 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 prepaid and the Buyer will be billed for the repair and return transportation charges (FCA Shipping Point). Warranty service is available outside the United States only if product was purchased through a Fluke Authorized Sales Outlet in the country of use or the applicable Fluke international price was paid. Product transported from the United States for which the applicable Fluke international price was not paid must be returned to the U.S. to receive warranty service, at the shipment expense and risk of Buyer. 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. THIS WARRANTY IS PURCHASER'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 of this warranty. Fluke Corporation P.O. Box 9090 Everett WA 98206-9090 Fluke Europe B.V. P.O. Box 1186 5602 B.D. Eindhoven The Netherlands
Safety Information
This meter complies with EN 61010-1:1993, ANSI/ISA S82.01-1994 and CAN/CSA C22.2 No. 1010.1-92 Overvoltage Category II. Use the meter only as specified in the Users Manual, otherwise the protection provided by the meter may be impaired. A Warning identifies conditions and actions that pose hazards to the user; 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 meter's 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 meter's fuses (see "How to Test the Fuse").
· · · · · · · · · · · · · · ·
Safety-1
· · · · ·
Never touch the probe to a voltage source when the test leads are plugged into the 10 A input jack. 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 meter's 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 Symbol Meaning Important information. See manual. Ground Fuse Double insulation (Protection Class II) Conforms to European Union directives
· ·
Safety-2
Table of Contents
Chapter 1
Title
Page
Introduction and Specifications........................................................ 1-1 1-1. 1-2. 1-3. 1-4. Introduction .......................................................................................... Organization of the Service Manual..................................................... Conventions.......................................................................................... Specifications ....................................................................................... 1-3 1-3 1-4 1-4
2
Theory of Operation........................................................................... 2-1 2-1. 2-2. 2-3. 2-4. 2-5. 2-6. 2-7. 2-8. 2-9. 2-10. 2-11. 2-12. 2-13. 2-14. 2-15. 2-16. 2-17. 2-18. 2-19. 2-20. Introduction .......................................................................................... Functional Block Description............................................................... Detailed Circuit Description ................................................................ Input Overload Protection................................................................ Rotary Switch................................................................................... Input Signal Conditioning Circuits .................................................. Volts............................................................................................. Ohms............................................................................................ Analog Section of Integrated Meter IC (U4) ................................... Microcomputer Control ................................................................... Peripherals to U4.............................................................................. AC Buffer .................................................................................... AC Converter............................................................................... Active Filter ................................................................................. A/D Converter ............................................................................. Beeper .......................................................................................... Reference Voltage ....................................................................... Power Supply............................................................................... Display ............................................................................................. Rotary Knob Switch and Potentiometer .......................................... 2-3 2-3 2-5 2-5 2-5 2-5 2-6 2-6 2-6 2-8 2-9 2-10 2-10 2-10 2-10 2-10 2-10 2-10 2-11 2-11
3
Maintenance ....................................................................................... 3-1 3-1. 3-2. 3-3. 3-4. 3-5. Introduction .......................................................................................... Required Tools and Equipment............................................................ Operator Maintenance .......................................................................... Disassembing the Case..................................................................... Removing and Reinstalling the Circuit Assembly...........................
i
3-3 3-3 3-4 3-5 3-5
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3-6. 3-7. 3-8. 3-9. 3-10. 3-11. 3-12. 3-13. 3-14. 3-15. 3-16. 3-17. 3-18. 3-19. 3-20. 3-21. 3-22. 3-23. 3-24. 3-25. 3-26. 3-27. 3-28. 3-29. 3-30. 3-31. 3-32. 4
Reassembling the Case..................................................................... Replacing the Battery....................................................................... Testing Fuses ................................................................................... Replacing Fuses ............................................................................... Cleaning ........................................................................................... Input Terminals............................................................................ Function Encoding Potentiometer ............................................... Performance Test.................................................................................. Testing the Display .......................................................................... Testing Function Selection (Rotary Switch).................................... Testing the AC Voltage Function .................................................... Testing the Frequency Counter Function......................................... Testing Frequency Sensitivity and Trigger Level............................ Testing the DC Voltage Function .................................................... Testing the DC mV Function ........................................................... Testing the Ohms Function .............................................................. Testing the Diode Test Function...................................................... Testing the mA Functions ................................................................ Testing the Amp Functions .............................................................. Testing the Inductive Pickup............................................................ Calibration............................................................................................ Troubleshooting the Power Supply ...................................................... Common (Shunt) Regulator Troubleshooting.................................. VDD (Series) Regulator Troubleshooting ....................................... Troubleshooting a Function Selection Malfunction............................. Meter Does Not Turn Off (Problem 1) ............................................ Meter Enters Wrong Function (Problem 2) .....................................
3-6 3-7 3-7 3-7 3-8 3-8 3-8 3-9 3-9 3-10 3-10 3-11 3-12 3-12 3-13 3-13 3-13 3-13 3-14 3-14 3-18 3-19 3-21 3-23 3-23 3-24 3-24
List of Replaceable Parts .................................................................. 4-1 4-1. 4-2. 4-3. 4-4. 4-5. 4-6. Introduction .......................................................................................... How to Obtain Parts ............................................................................. Manual Status Information................................................................... Newer Instruments................................................................................ Service Centers..................................................................................... Parts Lists ............................................................................................. 4-3 4-3 4-3 4-4 4-4 4-4
5
Schematic Diagrams.......................................................................... 5-1
ii
List of Tables
Table 1-1. 2-1. 3-1. 3-2. 3-3. 3-4. 3-5. 3-6. 3-7. 3-8. 3-9. 3-10. 3-11. 4-1. 4-2.
Title Summary of Accuracy Specifications.................................................................... Typical Voltage Levels and Tolerance.................................................................. Required Equipment .............................................................................................. Function Selection Test ......................................................................................... AC Voltage Test .................................................................................................... Frequency Test....................................................................................................... Frequency Counter Sensitivity and Trigger Level Tests ....................................... DC Voltage Test .................................................................................................... Ohms Test .............................................................................................................. Milliamp Tests ....................................................................................................... Amp Tests .............................................................................................................. Functional Description of Power Supply Components ......................................... Voltage Levels ....................................................................................................... Fluke 88 Final Assembly ....................................................................................... A1 Main PCA ........................................................................................................
Page 1-5 2-11 3-3 3-10 3-11 3-11 3-12 3-12 3-13 3-14 3-14 3-20 3-20 4-5 4-7
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List of Figures
Figure 2-1. 2-2. 2-3. 3-1. 3-2. 3-3. 3-4. 3-5. 3-6. 3-7. 4-1. 4-2. 5-1.
Title Overall Functional Block Diagram........................................................................ A/D Conversion ..................................................................................................... Function-Encoding Switch .................................................................................... Battery and Fuse Replacement .............................................................................. Assembly Details ................................................................................................... Display Test ........................................................................................................... Setup for Inductive Pickup Test ............................................................................ Waveform for Inductive Pickup Test..................................................................... Calibration Adjustment Points............................................................................... Simplified Power Supply Schematic ..................................................................... Fluke 88 Final Assembly ....................................................................................... A1 Main PCA ........................................................................................................ A1 Main PCA ........................................................................................................
Page 2-4 2-8 2-12 3-4 3-6 3-9 3-16 3-17 3-19 3-22 4-6 4-9 5-3
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Service Manual
POWER-UP OPTIONS
88
AUTO RANGE RECORD
_ +
AUTOMOTIVE METER
MIN AVG
DISPLAY
POWER-UP OPTIONS PRESS 2 SEC. WHILE TURNING METER ON LOW, OHMS/HIGH RESOLUTION
MAX
TRIG 20
H AC DC m s %+ T mVA M k Hz RPM 1 2
8 420 4000 mV
ZERO MIN MAX
DISABLE AUTOMATIC POWER-OFF HI ACCURACY, 1 SEC. RESPONSE AUTORANGE VDC, VAC HI IMPENDANCE mV DC INPUT TURN OFF BEEPER TEST ROTARY SWITCH
_ +
2
4
6
8
310
2
4
6
PUSHBUTTONS
ZERO MIN MAX RANGE HOLD
H
RANGE HOLD ALERT
RPM
SMOOTH Hz
%DUTY
ms-PULSE
ALERT
+ TRIGGER
RPM
ROTARY SWITCH
WARNING
TO AVOID ELECTRICAL SHOCK REMOVE TEST LEADS BEFORE OPENING CASE TO PREVENT DAMAGE OF INJURY INSTALL QUICK ACTING FUSES WITH AMP/VOLT RATINGS SHOWN.
mV V RPM V mA A mA A
OFF
ELECTRICAL SHOCK AND FUSE WARNINGS
mA COM V RPM
F 44/100A 1000V MIN INTERRUPT RATING 10 000A F 11A 1000V MIN INTERRUPT RATING 17 000A 9V NEDA 1604
SKID RESISTANT FEET
A
FUSE RATINGS
10A FUSED 400mA FUSED
CAT II 300V
PRODUCT S ERVICE
LR44340
BATTERY TYPE INPUT TERMINALS
FLUKE CORPORATION MADE IN USA PAT. RE. 34,428 DES. 314,715 DES. 312,534 4,217,543 4,556,867 4,532,470 5,073,757 4,940,204 4,951,834
FRONT
BACK
aad01f.eps
Frontispiece
vi
Chapter 1
Introduction and Specifications
Title 1-1. 1-2. 1-3. 1-4. Introduction .......................................................................................... Organization of the Service Manual..................................................... Conventions.......................................................................................... Specifications .......................................................................................
Page 1-3 1-3 1-4 1-4
1-1
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Service Manual
1-2
Introduction and Specifications Introduction
1
1-1. Introduction
This Service Manual provides information necessary to service the Fluke 88 Automotive Meter. This information includes the following: · · · · · · Specifications Theory of operation Calibration routines Performance testing and troubleshooting procedures Replacement parts lists Schematic diagrams
A meter under warranty will be promptly repaired or replaced (at Fluke's option) and returned at no charge. See the registration card for warranty terms. If the warranty has lapsed, the meter will be repaired and returned for a fixed fee. Contact the nearest Service Center for information and prices. To contact Fluke, call one of the following telephone numbers: USA: 1-888-99-FLUKE (1-888-993-5853) Canada: 1-800-36-FLUKE (1-800-363-5853) Europe: +31 402-678-200 Japan: +81-3-3434-0181 Singapore: +65-738-5655 Anywhere in the world: +1-425-446-5500 Or, visit Fluke's Web site at www.fluke.com.
1-2. Organization of the Service Manual
The Service Manual has five chapters. Chapter 1. Introduction and Specifications Chapter 1 describes the Service Manual and explains conventions used to describe the meter's circuitry. A complete set of specifications appears at the end of this chapter. Chapter 2. Theory of Operation Chapter 2 treats the meter's circuitry as functional blocks, with a description of each block's role in overall operation. A detailed circuit description is then given for each block. These descriptions explore operation to the component level and support the troubleshooting and repair procedures in Chapter 3. Chapter 3. Maintenance Chapter 3 provides complete maintenance information, detailed troubleshooting and repair procedures to the component level, and performance tests. Troubleshooting and repair procedures rely on the theory of operation in Chapter 2 and the schematic diagrams in Chapter 5. Chapter 4. List of Replaceable Parts Chapter 4 provides parts lists for all assemblies and information on how to order parts.
1-3
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Service Manual
Chapter 5. Schematic Diagrams Chapter 5 provides the schematic diagrams. A list of mnemonic definitions is included to aid in identifying signal name abbreviations.
1-3. Conventions
The following conventions are used in this manual: · · · Instrument Reference The term "Meter" is used when discussing the Fluke 88 Automotive Meter. Printed Circuit Assembly The term "pca" is used to mean a printed circuit board and its attached parts. Signal Logic Polarity Signal names followed by a minus sign (-) are active (or asserted) low. Signals not so marked are active high. · Circuit Nodes Individual pins or connections on a component are specified by a dash (-) following the component reference designator. For example, pin 19 of U30 would be U30-19. · User Notation Pushbuttons, positions on the rotary switch, input terminals, and the display are genrally shown in the manual as they appear on the Meter. Mnemonics used in the text that describe Meter circuitry are the same as those used on the schematic diagrams in Chapter 5.
1-4. Specifications
Specifications for the Fluke 88 follow. Accuracy is specified at 18°C to 28°C (64°F to 82°F) with relative humidity up to 90%, for a period of one year after calibration. AC Conversions are ac-coupled, average responding, and calibrated to the RMS value of a sine wave input. Note The Fluke 88 has a Lo-Ohms/High Resolution power-up option. In the LoOhms/High Resolution mode, the resolution is ten times that in the following specifications. To enter the Lo-Ohms/High Resolution mode, press and hold down the SMOOTH button, while turning the rotary switch to a function setting. Table 1-1 provides a summary of the accuracy specifications for basic meter functions. The complete Meter specifications follow Table 1-1. In the complete specifications, accuracy is given as: ±([% of Reading] + [Number of Least Significant Digits])
1-4
Introduction and Specifications Specifications
1
Table 1-1. Summary of Accuracy Specifications Function Volts AC AV Volts DC d V Resistance e Milliamps/Amps DC mA A d Frequency Hz Input Terminal Limits Rotary Switch Function ~V FV RPM F mV R G mA A~ mA AF Red Lead Min Display Reading 0.01 mV 0.0001 V 0.01 mV 0.01 (Lo-Ohms) 0.0001V 0.1 mA 0.001 mA 0.1 mA 0.001 Max Display Reading 1000 V 1000 V 400.0 mV 400.0 M 3.000 V 20.00 A** 400.0 mA 20.00 A** 400.0 mA Maximum Input ** Bassic Accuracy (± % of Reading) 1.5% 0.15% 0.2% 0.8% 0.01%
VG RPM V G VG VG A mA A mA
300 V 300 V 300 V 300 V 300 V 10 A/300 V* 400 mA/300 V 10A/300 V* 400 mA/300 V
* 10A continuous, 20A overload for 30 seconds maximum. 7 ** 10 V-Hz maximum. Volts AC Accuracy * Range 400.0 mV 4.000 V 40.00 V 300.0 V 300 V Resolution 0.1 mV 0.001 V 0.01 V 0.1 V 1V 45 Hz to 1 kHz ±(1.5%+10) ±(1.5%+5) ±(1.5%+5) ±(1.5%+5) ±(2.5%+5) 1 kHz to 5 kHz ±(1.9%+10) ±(1.9%+5) ±(1.9%+5) ±(1.9%+5) ±(2.5%+5)
*Below a reading of 200 counts, add 10 digits.
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Volts DC Range 4.000 V 40.00 V 300.0 V 300 V Millivolts DC Range 400.0 mV Resistance Range 400.0 4.000 k 40.00 k 400.0 k 4.000 M 40.00 M 400.0 M** Resolution 0.1* 0.001 k 0.01 k 0.1 k 0.001 M 0.01 M 0.1 M Accuracy ±(0.2%+2) ±(0.2%+2) ±(0.2%+2) ±(0.2%+2) ±(0.2%+2) ±(1%+3) ±(1%+20) Resolution 0.1 mV Accuracy ±(0.15%+2) Resolution 0.001 V 0.01 V 0.1 V 1V Accuracy ±(0.15%+2) ±(0.15%+2) ±(0.15%+2) ±(0.3%+2)
* In Lo-Ohms/High Resolution Mode, increases to 0.01. **This range will not be entered by Autorange. It must be selected manually. Diode Test Range 3.000 V mA/A DC Range Resolution Accuracy ±(0.8%+2) ±(0.8%+2) ±(0.8%+2) ±(1.3%+2) Burden Voltage (typical) 2.3 mV/mA 2.3 mV/mA 0.03 V/A 0.03 V/A Resolution 0.001 V Accuracy ±(2%+2)
40.00 mA 400.0 mA 4000 mA 10.00 A*
0.01 mA 0.1 mA 1 mA 0.01A
* 10A continuous, 20A overload for 30 seconds maximum.
1-6
Introduction and Specifications Specifications
1
mA/A AC (45 Hz to 2 kHz) Range Resolution Accuracy ** ±(3%+10) ±(3%+5) ±(1.5%+5) ±(1.5%+5) Burden Voltage (typical) 2.3 mV/mA 2.3 mV/mA 0.03 V/A 0.03 VA
40.00 mA 400.0 mA 4000 mA 10.0 A*
0.01 mA 0.1 mA 1 mA 0.01 A
* 10 A continuous, 20 A overload for 30 seconds maximum. ** Below reading of 200 counts, add 10 digits. Frequency, RPM, Duty Cycle, and Pulse Width Function Frequency** (0.5 Hz to 200 kHz, Pulse Width >2 µs) RPM 1 RPM 2 % Duty Cycle*** Pulse Width *** Range 199.99 1999.9 19.999 kHz 199.99 kHz >200 kHz 30-9,000 60-12,000 Resolution 0.01 Hz 0.1 Hz 0.001 kHz 0.01 kHz 0.1 kHz 1 RPM 1 RPM Accuracy ±(0.01%+1) ±(0.01%+1) ±(0.01%+1) ±(0.01%+1) Unspecified ± 2 RPM ± 2 RPM Pulse Width Range (ms)* 1999.9 5.00 0.500 0.0500 Resolution (ms) 0.1 0.01 0.001 0.0001
0.0-99.9% (0.5 Hz to 200 kHz, Pulse Width > 2 µs) 0.002-1999.9 ms (4 Hz to 200 kHz, Pulse Width > 2 µs)
* Pulse Width range is determined by the frequency of the signal. ** Frequency measurements can be made on voltage or current inputs. The current inputs are always dc-coupled. *** For rise times < 1 µs. Duty Cycle accuracy: within ±(0.2% per kHz + 0.1%). Pulse Width accuracy: ±(00.002 ms + 3 digits). Counter Sensitivity and Trigger Level Input Range* Minimum Sensitivity @ 0.5 Hz-200 kHz (RMS Sinewave) 70 mV (to 400 Hz) 150 mV 0.7 V 7V 70 V (140 kHz) Approximate Trigger Level (DC Voltage Function) 40 mV 1.7 V 4V 40 V
400.0 mV dc 400.0 mV ac 4.000 V 40.00 V 300.0 V
Maximum input for specified accuracy = 10 × Range or 300 V.
1-7
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Service Manual
Common and Normal Mode Rejection Ratio Function Overload Protection* Input Impedance (nominal) 10 M, <100 pF 10 M, <100 pF 10 M, <100 pF (ac-coupled) Open Circuit Test Voltage Common Mode Rejection Ratio (1 k unbalance) Normal Mode Rejection Ratio
FV F mV BV
300 V rms 300 V rms 300 V rms
>120 dB at dc, 50 Hz, or 60 Hz >120 dB at dc, 50 Hz, or 60 Hz >60 dB, dc to 60 Hz
>60 dB at 50 Hz or 60 Hz >60dB at 50 Hz or 60 Hz
Full Scale Voltage To 4.0 m <450 mV dc 40 M or nS <1.3V dc
Short Circuit Current
Diode Test * 10
7
300 V rms 300V rms
<1.3 V dc <3.9 V dc
<500 µA 1.0 mA typical
3.000 V dc
V-Hz max.
MIN MAX Recording Nominal Response 100 ms to 80% 1 sec Accuracy Specified accuracy ± 12 digits for changes > 200 ms in duration Same as specified accuracy for changes > 2 seconds in duration
1-8
Introduction and Specifications Specifications
1
General Maximum Voltage between any Terminal and Earth Ground Fuse Protection mA A Display (LCD) Digital 300 V 1 A 600 V FAST FUSE 15 A 600 V FAST FUSE Counts: Update Rate: 4,000 19,999 in High Resolution, 4½ -digit Mode only. 1/sec in High Resolution, 4½ - digit mode only. 3/sec in RPM, Frequency, % Duty Cycle, and Pulse Width 4/sec in all other functions and ranges.
Analog
Frequency and RPM Backlight Meter Operating Temperature Meter Storage Temperature Temperature Coefficient Relative Humidity Altitude Inductive Pickup Input Output Maximum RPM Battery Type Battery Life Shock, Vibration Size (HxWxL) Meter only With Holster & FlexStand Weight Meter only With Holster & FlexStand Safety Meter
2 x 32 Segments Updates Rate: 40/sec Counts: 19,999 Update Rate: 3/sec @ > 10 Hz Backlight turns on for 68 seconds, then turns off automatically if not turned off by user. -20°C to 55°C (-4°F to 131°F) -40°C to 60°C (-40°F to 140 °F) 0.05 x (Specified Accuracy)/ °C (<18°C or >28°C or 64°F or 82°F) 0% to 90% (0°C to 35°C; 32°F to 95°F) 0% to 70% (35°C to 55°C; 95°F to 131°F) 2000 meters maximum
Magnetic Field from Spark Plug Pulse to Trigger 12,000 (RPM 2) 9 V, NEDA 1604 or 6F22 or 006P 500 hrs typical with alkaline PER MIL-T-28800 for a Class 2 instrument.
1.25 in x 3.41 in x 7.35 in (3.1 cm 8.6 cm x 18.6) 2.06 in x 3.86 in x 7.93 in (5.2 cm x 9.8 cm x 20.1 cm)
12.5 oz (355 g) 22.0 oz (624 g)
Pickup
Complies with EN61010-1:1993, ANSI/ISA S82.01-1994, CAN/CSA 22.2 No. 1010.1:1992 Overvoltage Category II. UL License, TUV License, CSA License. Specified for spark-plug wire use only.
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1-10
Chapter 2
Theory of Operation
Title 2-1. 2-2. 2-3. 2-4. 2-5. 2-6. 2-7. 2-8. 2-9. 2-10. 2-11. 2-12. 2-13. 2-14. 2-15. 2-16. 2-17. 2-18. 2-19. 2-20. Introduction .......................................................................................... Functional Block Description............................................................... Detailed Circuit Description ................................................................ Input Overload Protection................................................................ Rotary Switch................................................................................... Input Signal Conditioning Circuits .................................................. Volts............................................................................................. Ohms............................................................................................ Analog Section of Integrated Meter IC (U4) ................................... Microcomputer Control ................................................................... Peripherals to U4.............................................................................. AC Buffer .................................................................................... AC Converter............................................................................... Active Filter ................................................................................. A/D Converter ............................................................................. Beeper .......................................................................................... Reference Voltage ....................................................................... Power Supply............................................................................... Display ............................................................................................. Rotary Knob Switch and Potentiometer ..........................................
Page 2-3 2-3 2-5 2-5 2-5 2-5 2-6 2-6 2-6 2-8 2-9 2-10 2-10 2-10 2-10 2-10 2-10 2-10 2-11 2-11
2-1
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2-2
Theory of Operation Introduction
2
2-1. Introduction
Chapter 2 provides the theory of operation for the Fluke 88. An overview of circuit operation is presented in the form of functional block descriptions. Detailed circuit descriptions cover the major circuit functions in more detail. Schematic diagrams are in Chapter 5.
2-2. Functional Block Description
Figure 2-1 is a block diagram of the Fluke 88 Automotive Meter. The Meter is partitioned into analog and digital sections. The integrated meter chip (U4) performs both analog and digital functions. The analog section of U4 contains the analog-to-digital (a/d) converter, active filter, ac converter, frequency comparator, analog signal routing, range switching, and power supply functions. The digital logic portion of U4 provides the state machine for synchronous a/d converter control and the 16-bit counter used for a/d converter counts and frequency measurements. Also, the digital logic section contains bus and interrupt control circuits (to facilitate the microcomputer interface) and registers for analog switch drive. The microcomputer section of U4 executes software functions, formats data for the display, drives the display, and controls most analog and digital logic functions. The pushbuttons initiate various operating modes for the microcomputer. Output from the microcomputer can be presented visually on the liquid crystal display (LCD) and audibly by the beeper.
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aad02f.tif
Figure 2-1. Overall Functional Block Diagram
2-4
Theory of Operation Detailed Circuit Description
2
2-3. Detailed Circuit Description
Each of the functional blocks in Figure 2-1 is discussed in greater detail in the following paragraphs. Refer to the schematic diagrams in Section 5 for details not shown in the figures in this section.
2-4.
Input Overload Protection Overload protection for the T input is provided by a network of two metal-oxide varistors (RV1 and RV2), three current-limiting resistors (R1, R2, and RT1), and spark gap E1. The 1-k, 2W fusible resistor R1 opens when an extremely high energy signal is present. Thermistor RT1 rises to a high impedance during a sustained voltage overload in the mV dc, ohms, or diode test functions. A voltage clamp network is formed by transistors Q1, Q2, and Q6, diodes CR7 and CR8, and resistor R58. During ohms and diode test overloads, this clamp circuit limits the overload current to U4 to 10 mA.
Power supply regulation and system operation is maintained during any of these overloads. Overload protection for the mA input is provided by F1, rated at 1A/600V. The A input is protected by F2, rated at 15A/600V. In addition, the microamp shunt resistors (R4 and R43) are protected from overload currents below the F1 fusing level by the U1 and CR1 diode network. The Input Alert feature provides a beeper warning signal when an input jack is connected to a current input (mA or A) and the rotary switch is not set to a current function (mA or A). The Meter detects the presence of an input connection by using split jacks at the mA and A inputs. One side of the jack is connected to an overload protection resistor (R7 for mA, R10 for A). R7 and R10 are connected to U4 sense lines AP4 and AP5 (pins 89 and 88). Resistors R8 and R48 provide VDD pull up for AP4, and R11 is the pull up resistor for AP5. When a connection is made at mA or A, the sense side of the jack is pulled to COM. This condition is detected and compared with the selected function by U4. If a conflict exists, the beeper warning is activated.
2-5.
Rotary Switch Input signals are routed from the overload protection circuits to a double-sided switch wafer, which provides the necessary switching to implement the various signal conditioning. Input Signal Conditioning Circuits Each input signal is routed through signal conditioning circuitry before reaching U4. Input signals received through the T input are routed through Z1, a precision resistor network. This input divider network provides precise input scaling for the various voltage ranges and precision reference resistors for the ohms and capacitance functions. The capacitors in parallel with the various resistors in Z1 are used for high frequency compensation.
The input divider is used in two modes: in voltage functions, a series mode is used to provide four divider ratios; in the ohms function, a parallel mode provides five reference resistors. During the following discussion, refer to the schematic and signal flow diagrams in Section 5.
2-6.
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2-7.
Volts In voltage functions, signal flow for input divider Z1 begins with the unknown voltage at the T input, which is connected to the high end of the 9.996-M resistor (pin 1 of Z1) through R1 and RT1. In ac volts, C1 is also connected in series. In dc volts, C1 is shorted by S1 (contacts 3 and 4). Internal switches connect the 9.996-M and 1.1111M resistors (pin 2 to pin 3 of Z1). The low end of the 1.1111-M resistor (pin 7 of Z1) is connected to COM through S1 contacts 1 and 2, producing the divide-by-10 ratio used in the 400 mV ac, 4V ac, and 4V dc ranges.
For the 40V range, internal switches connect a 101.01-k resistor to provide a divideby-100 ratio. In the 300.0V range, 10.01 k is used for a divide-by-1000 ratio. And a 1.0001-k resistor is used in the 300V range to provide a divide-by-10000 ratio. The internal switch resistance connecting the 1.1111 M and 9.996 M with the other resistors is approximately 4 k. Since the a/d converter senses the voltage at APV1 of U4 (pin 3 of Z1), the internal switch resistance adds to the 9.996-M resistor, making for a circuit total of 10 M.
2-8.
Ohms In the 400-ohm range the internal switches connect the 9.996-M resistor (pin 2 of Z1) to the 1.0001-k resistor (pin 6 of Z1); contacts 5 and 3 of S1 connect the remaining ends to these resistors, making a reference resistor of 1 k. Again, the 4-k internal switch resistance adds to the 9.996 M.
The source voltage is connected internally at both APV0 and APV4 of U4. The current is routed through the 1.0001-k and 9.996-M resistors, into S1 at contacts 3 and 5, out of S1 at contact 4, through R1 and RT1, out the T input, through the unknown resistance, and back to COM. The same current flows through the unknown resistance and the reference resistor. The voltage dropped across the unknown resistance is sensed from the T input jack through R2 and S1 (contacts 11 and 12) to AP1 of U4. The a/d converter senses the voltage drop across the 1K reference resistor through the low (AP2 of U4 through R13) and high (APV0 and APV4) points. These two voltages are used by the a/d converter to perform a ratiometric measurement. For the 4-k range, the 10.010-k resistor used in parallel with the 9.996-M resistor forms a 10-k reference resistor. In the 40-k range, 101.01 k and 9.996 M form a 100-k reference resistor. And in the 400-k range, 1.1111 M and 9.996 M provide a 1-M reference resistor. The 4 M and 40 M use only the 9.996-M resistor.
2-9.
Analog Section of Integrated Meter IC (U4) The analog-to-digital converter, autorange switching, frequency comparator, and most of the remaining analog circuitry are contained in the analog section of U4. Peripherals to this U4 analog section include the crystal clock, the system reference voltage, and some filter and amplifier resistors and capacitors.
Analog-to-digital conversion is accomplished within U4 using the dual-rate, dual-slope a/d converter circuit shown in Figure 2-2. For most measurements, the basic a/d conversion cycle lasts 25 ms, for 40 measurements per second. A single conversion at this rate is called a minor cycle sample. Each minor cycle sample is used to provide 40 updates per second for the fast response bar graph display, fast MIN MAX recording, and fast autoranging. Eight minor cycle samples are necessary to accumulate data for displaying a fullresolution (4000 count full scale) measurement on the digital display. A 40-ms autozero
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Theory of Operation Detailed Circuit Description
2
phase occurs following every eight-sample sequence. Therefore, each digital display update requires 240 ms, approximating 4 updates per second. Basic a/d conversion elements and waveforms are shown in Figure 2-2. As this figure shows, a residual charge is retained by the integrator capacitor due to the overshoot past the true-zero base line. In the absence of an autozero phase, the residual charge would normally produce a significant error in the sample taken next. However, a digital algorithm eliminates the error and accounts for the residual as it propagates through all eight samples. Basic timing for the a/d converter is defined as a series of eight integrate read cycles, followed by a 40-ms autozero phase. However, the 40-M, 400-M, overload recovery, autoranging, Touch Hold, 100-ms MIN MAX, and rotary switch potentiometer modes all require variations from the basic timing. A voltage comparator, with microcomputer configurable offsets, is used for both signal detection in counter modes and threshold detection in continuity mode. In counter modes, digital pulses from the voltage comparator are routed to the 16-bit counter.
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Figure 2-2. A/D Conversion
2-10. Microcomputer Control A 4-bit microcomputer, integrated within U4, controls the various Meter functions and drives the display. A/D converter and counter measurements are controlled via
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Theory of Operation Detailed Circuit Description
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microcomputer interface lines. The MIN MAX, Touch Hold, and ZERO (relative) modes involve additional data processing by the microcomputer to generate the display value. Note that the microcomputer runs on its own RC clock at a frequency of 525 to 800 kHz and is asynchronous from the crystal clock. The microcomputer exercises direct control over the ranging and signal routing analog switches. A specific word is written to the switch drive register for each function/range selection. When the Meter is in autorange, the microcomputer determines the correct range based on the input. In addition, for autoranging during voltage, ohms, or current measurements, the active filter fast mode is enabled for quick response. In the frequency or duty cycle mode, pressing the RANGE button causes a range change in the primary function (volts, amps, etc.) that may change the sensitivity or offset. The microcomputer sets the required a/d converter mode, which determines the on-chip analog signal ports to be used for the integrate and de-integrate signals. The microcomputer also selects one of the three available gain resistors in Z1 for integrate and de-integrate. All voltage and current conversions use either a 400-mV or a 40-mV full scale mode. Other modes are used for ohms, 4 M, 40 M, and 400 M. Since the a/d state machine timing is under direct software control, a mode invoked in another function or range can use different timing. Counter measurements are also controlled by the microcomputer section of U4. The microcomputer initializes the counters, monitors the count accumulation, arms and disarms the logic signal gating, and calculates the display value from the counter values. MIN MAX Recording, Touch Hold, and ZERO (relative) are secondary software functions. This means that the microcomputer performs either a different control algorithm or a different math routine on the data, as explained below. · In the MIN MAX Recording function, the maximum and minimum readings after initialization are stored in memory, and a true running average is calculated after each reading. The running average is updated for a maximum of 36 hours. The user presses the MIN MAX pushbutton to scroll through the minimum, maximum, average, and present readings. In the 100 ms MIN MAX mode, a single measurement sample is used to calculate the display value; in the 1 second MIN MAX mode, a full resolution conversion is used. When the Touch Hold function is selected, the microcomputer does not allow a full resolution conversion to be completed unless the input signal is stable. When a stable reading occurs, the conversion is completed, and the microcomputer generates and freezes the corresponding display. The microcomputer now waits for a change in the signal to exceed a certain threshold, then begins watching for a stable reading again. Note that a reading is forced when Touch Hold is first selected. Also, open test lead signals do not update the display. When the ZERO function is selected, the microcomputer stores the present reading as an offset. This value is subtracted from all subsequent readings (provided that they are on scale) to give the display value.
·
·
2-11. Peripherals to U4 In addition to input overload protection and input signal conditioning circuits, other devices peripheral to U4 are needed to support Meter features. The ac converter, active filter, and a/d converter circuits require off-chip resistors and capacitors. Digital drive and level-shifting circuits are needed for the beeper drive, quick turn off, and LCD backlight features. A voltage reference is generated separately from U4, and some discrete resistors and transistors support the power supply.
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2-12. AC Buffer On the Meter, R14, R15, C5, and C27 are part of the ac buffer circuit that drives the ac converter and guard. The Meter's ac buffer can be configured for an ac gain of 1 or 10. 2-13. AC Converter The Meter's average ac converter uses off-chip components R30, R31, R34, R40, C24, C28, and C29. This ac converter is a full-wave rectifying converter with a differential output and gain selected to give a dc output equal to the rms value for a sine wave input. Filtering is provided by C28 and C29. 2-14. Active Filter The active filter uses off-chip passive components R17, R18, C8, and C9. It is a second order, low pass filter with two poles at 5.9 Hz in normal mode that filters input signal noise and ac ripple from the ac converter, yielding stable a/d converter readings. The microcomputer can disable the filter completely or enable the filter fast response mode. 2-15. A/D Converter Pins 8, 9, and 10 on precision resistor network Z1 connect to the three a/d converter gain resistors. Pin 8 connects to 190 k for a gain of 0.87. Pin 9 connects to 160 k for a gain of 1, and pin 10 connects to 16 k for a gain of 10. Pin 11 is the common connection. The autozero capacitor (C10) stores op amp and comparator offsets. The integration capacitor is C11. 2-16. Beeper Devices Q9, Q11, R56, R57 and CMOS hex inverter U6 make up the double-ended beeper drive circuit. Transistor Q12 is connected to provide quick microcomputer power down when the Meter is turned off. 2-17. Reference Voltage The system reference voltage (1.235V) is generated by VR1 and R44. The 1.000V reference voltage for the a/d converter is supplied through U4-1 (REFI). This voltage is adjusted by R21, the dc calibration potentiometer. In addition to generating the a/d reference, the VR1 voltage is used for power supply reference, voltage comparator selectable offset generation, and the ohms source level. 2-18. Power Supply The power supply consists of two regulators, one shunt and one series, which set VDD at +3.0V and VSS at -3.2V for all battery voltages down to 6.7V. The shunt (common) regulator sets |VDGND - VSS| (VDGND = COM = 0V) and consists of an uncompensated op amp and large current shunt devices integrated on U4. Resistors R37 and R38 provide voltage division. The series (VDD) regulator, which sets |VDD VDGND|, is made up of another on-chip, uncompensated op amp, along with devices Q3, R24, and R25. Q3 is the series regulator element, and R24 and R25 are for voltage sensing. Capacitors C14 and C21 provide circuit compensation and power supply decoupling for the shunt and series regulators, respectively. Voltage level information is presented in Table 2-1. See Figure 3-7 for a simplified schematic of the power supply.
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Theory of Operation Detailed Circuit Description
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Table 2-1. Typical Voltage Levels and Tolerance Signal VDD VSS VBT+ VBTREFH PS0 PS1 AP6 VOA VOB 3.0 ±0.3 3.2 ±0.3 3.5 ±0.3 5.5 (battery at full 9 V charge) 3.0 (battery at low charge of 6.5 V) 1.235 ±0.012 1.235 ±0.015 0 ±0.15 -0.5 to -0.15 2.2 to 1.7 (referenced from VSS) 1.07 to .85 (referenced from VSS) Typical Voltage Levels
2-19. Display The liquid-crystal display (LCD) operates under direct control of the microcomputer. Characters are generated by the computer and displayed on the LCD. Both digital readings and the analog pointer are displayed in conjunction with annunciators. The Fluke 88 features a transflective LCD with a light-emitting diode (LED) backlight. Refer to the Fluke 88 Users Manual for a more detailed description of the display. 2-20. Rotary Knob Switch and Potentiometer Input signals are routed from the overload protection circuits to a double-sided swtch wafer, which provides the necessary switching to implement the various signal conditioning. The function-encoding potentiometer is attached to the associated rotary switch shaft. After turn on, or a knob position change, U4 performs a voltage ratio measurement on this potentiometer to determine the new function. See Figure 2-3.
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Figure 2-3. Function-Encoding Switch
2-12
Chapter 3
Maintenance
Title 3-1. 3-2. 3-3. 3-4. 3-5. 3-6. 3-7. 3-8. 3-9. 3-10. 3-11. 3-12. 3-13. 3-14. 3-15. 3-16. 3-17. 3-18. 3-19. 3-20. 3-21. 3-22. 3-23. 3-24. 3-25. 3-26. 3-27. 3-28. 3-29. 3-30. 3-31. 3-32. Introduction .......................................................................................... Required Tools and Equipment............................................................ Operator Maintenance .......................................................................... Disassembing the Case..................................................................... Removing and Reinstalling the Circuit Assembly........................... Reassembling the Case..................................................................... Replacing the Battery....................................................................... Testing Fuses ................................................................................... Replacing Fuses ............................................................................... Cleaning ........................................................................................... Input Terminals............................................................................ Function Encoding Potentiometer ............................................... Performance Test.................................................................................. Testing the Display .......................................................................... Testing Function Selection (Rotary Switch).................................... Testing the AC Voltage Function .................................................... Testing the Frequency Counter Function......................................... Testing Frequency Sensitivity and Trigger Level............................ Testing the DC Voltage Function .................................................... Testing the DC mV Function ........................................................... Testing the Ohms Function .............................................................. Testing the Diode Test Function...................................................... Testing the mA Functions ................................................................ Testing the Amp Functions .............................................................. Testing the Inductive Pickup............................................................ Calibration............................................................................................ Troubleshooting the Power Supply ...................................................... Common (Shunt) Regulator Troubleshooting.................................. VDD (Series) Regulator Troubleshooting ....................................... Troubleshooting a Function Selection Malfunction............................. Meter Does Not Turn Off (Problem 1) ............................................ Meter Enters Wrong Function (Problem 2) .....................................
Page 3-3 3-3 3-4 3-5 3-5 3-6 3-7 3-7 3-7 3-8 3-8 3-8 3-9 3-9 3-10 3-10 3-11 3-12 3-12 3-13 3-13 3-13 3-13 3-14 3-14 3-18 3-19 3-21 3-23 3-23 3-24 3-24
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3-1. Introduction
Warning
Service procedures described in section 3 should performed by qualified service personnel only. To avoid electrical shock, do not perform any servicing unless you are qualified to do so. Chapter 3 covers the following procedures: · · · · · Maintenance Disassembly and reassembly Performance testing Calibration Troubleshooting to the component level
3-2. Required Tools and Equipment
Required equipment is listed in Table 3-1. If the recommended models are not available, equipment with equivalent specifications may be used. Repairs or servicing should be performed only by qualified personnel.
Table 3-1. Required Equipment Equipment DMM Calibrator Required Characteristics AC Voltage Range: 0-1000V ac Accuracy: ±0.3% Frequency Ranmge: 50-10000 Hz Accuracy: ±1% DC Voltage Range: 0-1000 V dc Accuracy: ±0.3% Current Range: 34-350 mA Accuracy: ±.2% Range: 190-100 M Accuracy: 0.1% Current Range:10A Accuracy AC (60 Hz to 1 kHz): ±0.35% DC ±0.3% Function Generator Triangle Wave N Cycle (Single Cycle) 1 MHz 20 V Output unterminated 60 MHz, 30% vertical error 10M scope probe Binding Post to BNC Male ±1% 1-ft, insulated Philips PM5133 or 5134 Recommended Model Fluke 5500A
Oscilloscope Adapter 10-Ohms Resistor 14-AWG Wire
Philips PM 3055 Pomona Model 1296 NA NA
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Table 3-1. Required Equipment (cont) Equipment Used in Performance Tests Performance Test AC Voltage Frequency Accuracy Sensitivity Trigger Level DC Voltage mV DC Ohms Diode Test mA A RPM/Inductive Pickup X X X X X X X X X X X DMM Calibrator X Function Generator Oscilloscope
3-3. Operator Maintenance
Warning
To avoid electrical shock, remove the test leads and any Input signals before replacing the battery or fuses. To Prevent damage or injury, install only quick-acting fuses With the amp/volt ratings shown in Figure 3-1.
aad05f.tif
Figure 3-1. Battery and Fuse Replacement
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Maintenance Operator Maintenance
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3-4.
Disassembing the Case Perform the following procedure to disassemble the case:
1. Disconnect the test leads from any live source, turn the Meter rotary switch to OFF, and remove the test leads from the front terminals. 2. The case top is secured to the case bottom by three screws and two internal snaps (at the LCD end). Using a Phillips-head screwdriver, remove the three screws from the case rear. Note The gasket between the case top and case bottom is sealed to the case bottom. The case top lifts away from the gasket easily. Do not damage the gasket or attempt to separate the gasket from the case bottom. 3. Turn the case over (display side up), and, lifting up on the input terminal end, disengage the case top from the gasket. Gently unsnap the case top at the display end. See Figures 3-1 and 3-2. Caution With its case removed, circuit connections are exposed. To avoid unintended circuit shorting, always place theuncovered Meter assembly on a protective surface.
3-5.
Removing and Reinstalling the Circuit Assembly After the outer case has been removed, perform the following procedure to disconnect the covering shields from the circuit assembly:
1. Unsnap the battery from the battery connector. 2. Carefully remove the assembly from the case bottom and turn the assembly over. 3. Remove the one Phillips-head screw securing the back shield to the circuit assembly. Then remove the back shield. 4. The front shield can now be disconnected from the circuit assembly by detaching the four snaps (one at a time) found on the front shield. Caution Detach the four securing snaps gently. Excessive force can deform or fracture the snaps. 5. To reattach the circuit assembly, push the front shield on so that the four clips engage gently and simultaneously. Then turn the assembly over, and replace the back shield and Phillips-head screw. Note Ensure that the shields are tightly attached. Meter accuracy depends on properly fitted shields. 6. Gently place the assembly back in the case bottom. 7. Snap the battery to the battery connector and reinsert the battery in the case bottom.
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Figure 3-2. Assembly Details
3-6.
Reassembling the Case Perform the following procedure to reassemble the case:
1. Make sure that the Meter rotary switch and circuit board switch are in the OFF position (see Figure 3-2).
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2. Dress the battery leads so that they will not be pinched between the case top and bottom. 3. Ensure that the gasket remains secured to the case bottom. 4. Starting with the two snaps at the display end and finishing at the terminal end, cradle the case top into the gasket. 5. Reinstall the three screws from the case bottom. 6. Execute the PERFORMANCE TEST procedures later in Chapter 3.
3-7.
Replacing the Battery
WWarning
To avoid false readings, which could lead to possible electric shock or personal injury, replace the battery as soon as the battery indicator (B) appears. The meter is powered by a single 9 V battery (NEDA 1604, 6F22, or 006P). Referring to Figure 3-1, perform the following procedure to replace the battery: 1. Remove the Meter case as described previously under "Disassembling the Case". 2. Lift the battery from the case bottom, and carefully unsnap the battery from the battery connector. 3. Snap the battery connector to the terminals of a new battery and reinsert the battery into the case bottom. Dress the battery leads so that they will not be pinched between the case bottom and case top. 4. Reassemble the Meter as described under "Reassembling the Case".
3-8.
Testing Fuses Perform the following procedure to test the internal fuses of the Meter.
1. Set the Meter rotary switch to m . 2. Plug a test lead into the z input terminal, and touch the probe to the A input terminal. Because the receptacles of the input terminals contain split contacts, be sure that you touch the probe to the half of the receptacle contact that is nearest the LCD. 3. The display should read between 00.0 and 00.5 ohms. This tests F2 (15 A, 600 V). If the display reads OL (overload), replace the fuse and test again. If the display reads any other value, further servicing is required. 4. Move the probe from the A input terminal to the mA input terminal. Touch the half of the receptacle that is nearest the LCD. 5. The display should read between 0.995 k and 1.005 k. This procedure tests F1 (1 A, 600 V). If the display reads a high resistance or OL (overload), replace the fuse and test again. If the display reads any other value, further servicing is required.
3-9.
Replacing Fuses
Warning
To prevent equipment damage or injury, install ONLY specified replacement fuses with the amperage, voltage, interrupt, and speed ratings listed in the List of Replaceable Parts later in this manual.
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Referring to Figures 3-1 and 3-2, perform the following procedure to examine or replace the meter's fuses: 1. Perform steps 1 through 3 of the battery replacement procedure. 2. Remove the defective fuse by gently prying one end of the fuse loose and sliding the fuse out of the fuse bracket. 3. Install a new fuse of the same size and rating. Make sure the new fuse is centered in the fuse holder. 4. Make sure that the Meter rotary switch and circuit board switch are in the OFF position. 5. Ensure that the gasket remains secured to the case bottom. Then, starting with the two snaps at the display end and finishing at the terminal end, cradle the case top into the gasket. 6. Reinstall the three screws from the case bottom.
3-10. Cleaning
Warning
To avoid electrical shock or damage to the meter, never allow water inside the case. To avoid damaging the meter's housing, never use solvents on the meter. If the Meter requires cleaning, wipe it with a cloth that is lightly dampened with water or a mild detergent. Do not use aromatic hydrocarbons, chlorinated solvents, or methanolbased fluids on the Meter.
3-11. Input Terminals Water, dirt, or other contamination in the A or mA terminals may activate the Input Alert (beeper) even though test leads are not inserted. Such contamination can sometimes be dislodged by turning the Meter over and gently tapping on the case. However, Fluke recommends the following procedure as a much more effective treatment:
1. Turn the Meter off and remove all test leads. 2. Use a clean swab in each of the four terminals to dislodge and clean out the contamination. 3. Moisten a new swab with a cleaning and oiling agent (such as WD40). Work this swab around in the A and mA input terminals. The oiling agent insulates the terminals from moisture-related shorting. This preventive treatment ensures against future erroneous Input Alerts.
3-12. Function Encoding Potentiometer Perform the following procedure to clean the rotary switch potentiometer, which is screened on the back of the pca:
1. Remove the circuit assembly as described previously in this section under "Removing and Reinstalling the Circuit Assembly". 2. From the back of the circuit assembly, push the switch shaft in (see Figure 3-2), and remove the polymer thick-film (PTF) contact assembly. 3. Push and secure the ptf contact assembly back on the switch shaft.
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4. Reassemble the circuit assembly, shields, and case parts as described previously in this section under "Removing and Reinstalling the Circuit Assembly" and "Reassembling the Case". 5. Execute the PERFORMANCE TEST after reassembly.
3-13. Performance Test
Perform the following procedure to check basic Meter operations: 1. Turn the Meter rotary switch to . 2. Plug a test lead into the z input. Using the probe end of the test lead, touch the half of the input contact nearest the LCD of the mA input. The display should read 1.000 k ± 5 digits. 3. Remove the test probe from the mA input. 4. Push the ALERT key on the bottom row of the softkeys. 5. Place the test probe in the A input, touching the contact nearest the LCD. The beeper sounds if the mA fuse (15A) is good. The following paragraphs provide a more complete check of the Meter's accuracy and operability. The accuracy of each Meter function is compared to the specifications for that function listed in Chapter 1 of this manual. The case covers do not need to be removed and no adjustments are necessary. Merely make the input connections called for, and read the display. If the Meter fails any of the performance tests below, calibration adjustment and/or repair is required. The equipment required to perform these tests is listed in Table 3-1. Specified accuracy is maintained for a period of one year after calibration, at an operating temperature of 18°C to 28°C and at a maximum of 90% relative humidity.
3-14. Testing the Display With the Meter rotary switch in the OFF position, press and hold down any pushbutton and turn the rotary switch to any function setting.
The display should appear as shown in Figure 3-3.
AUTO
_ +
RANGE
RECORD
MAX
MIN AVG
TRIG 20
H AC m s T m M k RPM
8
DC _ %+ V A Hz
1 2
_ +
2
4
6
8
310 2
4
6
420 4000 mV
aad07f.eps
Figure 3-3. Display Test
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3-15. Testing Function Selection (Rotary Switch) The function selection test checks the operation of the rotary switch function selector circuit.
The selector circuit relies on the interface between a PTF region on the circuit assembly and a rotating contact assembly on the switch shaft. The function selection test exercises this interface by checking the various range codes and displaying their representative numbers. Perform the following procedure to test the function selector circuit. 1. Press and hold down RPM pushbutton while turning the rotary switch from OFF to BV. This enables the function selection test and disables normal Meter functions. [T] (for test) is shown on the display, and a number appears in the display. 2. Compare the display reading with the value for BV shown in Table 3-2. This reading should be within ± 12 of the number for BV in Table 3-2. If it is not, refer to Troubleshooting A Function Selection Malfunction later in Chapter 3. 3. Rotate the switch to F V. The display reading should be within ±12 of the F V value shown in Table 3-2. 4. Test the remaining function settings on the rotary switch as in step 3. 5. To exit the function selection test, turn the rotary switch to OFF, then turn it to any switch setting.
Table 3-2. Function Selection Test Function OFF BV FV F mV G ^B µ[B Display (±12) n/a 0 -32 -64 -96 -128 -160 -192
3-16. Testing the AC Voltage Function Perform the following procedure to verify accuracy of voltage ranges.
1. Connect the calibrator to the z and COM inputs on the Meter. 2. Set the meter rotary switch to BV and press the range button for two seconds to select the auto-range. 3. Set the calibrator for the voltage and frequency called for in step 1 of Table 3-3. The display reading should be within the limits shown in Table 3-3. 4. Repeat the previous step (Step 2) for steps 2 through 14 of Table 3-3. 5. Turn the meter off.
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Table 3-3. AC Voltage Test Input Step 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Voltage 350.0 mV 350.0 mV 350.0 mV 3.500 V 3.500 V 3.500 V 35.00 V 35.00 V 35.00 V 350.0 V 350.0 V 350.0 V 900 V 900 V Frequency 60 Hz 1 kHz 5 kHz 60 Hz 1 kHz 5 kHz 60 Hz 1 kHz 5 kHz 60 Hz 1 kHz 5 kHz 60 Hz 5 kHz Display R