Fluke 187 Use and care manual

®
187/189
True RMS Multimeter
Calibration Manual
PN 1584337
November 2000
© 2000 Fluke Corporation, All rights reserved. Printed in U.S.A.
All product names are trademarks of their respective companies.

LIFETIME LIMITED WARRANTY
Each Fluke 20, 70, and 180 Series DMM purchased after October 1, 1996 will be free from defects in material and
workmanship for its lifetime. This warranty does not cover fuses, disposable batteries and damage from neglect, misuse,
contamination, alteration, accident or abnormal conditions of operation or handling, including overvoltage failures caused
by use outside the DMMs specified rating, or normal wear and tear of mechanical components. This warranty covers the
original purchaser only and is not transferable.
For ten years from the date of purchase, this warranty also covers the LCD. Thereafter, for the lifetime of the DMM, Fluke
will replace the LCD for a fee based on then current component acquisition costs.
To establish original ownership and prove date of purchase, please complete and return the registration card
accompanying the product. Fluke will, at its option, repair at no charge, replace, or refund the purchase price of a
defective product purchased through a Fluke authorized sales outlet and at the applicable international price. Fluke
reserves the right to charge for importation costs of repair/replacement parts if product purchased in one country is sent
for repair elsewhere.
If product is defective, contact your nearest Fluke authorized service center to obtain return authorization information,
then send the product to that service center, with a description of the difficulty, postage and insurance prepaid (FOB
Destination). Fluke assumes no risk for damage in transit. Fluke will pay return transportation for product repaired or
replaced in-warranty. Before making any non-warranty repair, Fluke will estimate cost and obtain authorization, then
invoice you for repair and return transportation.
THIS WARRANTY IS YOUR ONLY REMEDY. NO OTHER WARRANTIES, SUCH AS FITNESS FOR A PARTICULAR
PURPOSE, ARE EXPRESSED OR IMPLIED. FLUKE SHALL NOT BE LIABLE FOR ANY SPECIAL, INDIRECT,
INCIDENTAL OR CONSEQUENTIAL DAMAGES OR LOSSES, INCLUDING LOSS OF DATA, ARISING FROM ANY
CAUSE OR THEORY. AUTHORIZED RESELLERS ARE NOT AUTHORIZED TO EXTEND ANY DIFFERENT
WARRANTY ON FLUKE’S BEHALF. Since some states do not allow the exclusion or limitation of an implied warranty or
of incidental or consequential damages, this limitation of liability may not apply to you. If any provision of this warranty is
held invalid or unenforceable by a court or other decision-maker of competent jurisdiction, such holding will not affect the
validity or enforceability of any other provision.
Fluke Corporation Fluke Europe B.V.
P.O. Box 9090 P.O. Box 1186
Everett, WA 98206-9090 5602 BD Eindhoven
U.S.A. The Netherlands
11/99

i
Table of Contents
Title Page
Introduction ....................................................................................................... 1
Contacting Fluke ............................................................................................... 1
Precautions and Safety Information .................................................................. 2
International Symbols........................................................................................ 2
Safety Information............................................................................................. 3
Specifications .................................................................................................... 4
Accuracy ....................................................................................................... 4
Feature Summary.......................................................................................... 4
Basic Specifications .......................................................................................... 5
Detailed Accuracy Specifications ..................................................................... 6
Frequency Counter Sensitivity.......................................................................... 9
Burden Voltage (A, mA, µA)............................................................................ 9
Input Characteristics.......................................................................................... 9
Required Equipment.......................................................................................... 10
Basic Maintenance ............................................................................................ 11
Opening the Meter Case................................................................................ 11
Removing and Reinserting the Circuit Board Assembly.............................. 11
Replacing the LCD........................................................................................ 12
Reassembling the Meter Case....................................................................... 13
Testing Fuses (F1 and F2)............................................................................. 13
Replacing Fuses ............................................................................................ 14
Replacing the Batteries ................................................................................. 14
Cleaning........................................................................................................ 15
Performance Tests............................................................................................. 16
Testing the Display ....................................................................................... 16
Backlight Test............................................................................................... 16
Current Terminal Sensing Test..................................................................... 16
Keypad Test .................................................................................................. 17
Verification of the IR Communication Port.................................................. 17
Testing Temperature..................................................................................... 17
Testing Voltage, Current, Resistance, Capacitance and Diode Functions.... 18
Calibration......................................................................................................... 21
Keypad Interface........................................................................................... 21
General Procedure......................................................................................... 22
Special Requirements.................................................................................... 23
Calibration Inputs.......................................................................................... 23

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Remote Interface........................................................................................... 25
Temperature Calibration............................................................................... 25
Setup......................................................................................................... 25
Procedure.................................................................................................. 26
Re-Programming Serial Number or Model Number..................................... 26
Parts and Accessories........................................................................................ 27

iii
List of Tables
Table Title Page
1. International Symbols............................................................................................ 2
2. Required Tools and Equipment............................................................................. 10
3. Temperature Test Input and Display..................................................................... 17
4. Performance Test Steps ......................................................................................... 18
5. Calibration Inputs .................................................................................................. 23

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iv

v
List of Figures
Figure Title Page
1. Removing LCD Mask to Access LCD................................................................... 12
2. Testing the Current Fuses...................................................................................... 14
3. Battery and Fuse Replacement .............................................................................. 15
4. Display Test........................................................................................................... 16
5. Locating Recessed Calibration Button.................................................................. 21
6. Calibration Display................................................................................................ 22
7. Replacement Parts and Accessories....................................................................... 28

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1
Introduction
WWarning
To avoid shock or injury, do not perform the verification tests
or calibration procedures described in this manual unless you
are qualified to do so.
The information provided in this document is for the use of
qualified personnel only.
Caution
The 187 & 189 Multimeters contain parts that can be damaged
by static discharge.
Follow the standard practices for handling static sensitive
devices.
The information in this manual deals with the Fluke Models 187 & 189 True RMS
Multimeters, (hereafter referred to as “the meter”). Information provided includes:
•Precautions and safety information
•Specifications
•Basic maintenance (cleaning, replacing the battery and fuses)
•Performance test procedures
•Calibration and calibration adjustment procedures
•Accessories and replaceable parts
For complete operating instructions, refer to the Model 187 & 189 Users Manual located
on the 187/189 CD ROM.
Contacting Fluke
To order accessories, receive assistance, or locate the nearest Fluke distributor or Service
Center, call:
USA: 1-888-99-FLUKE (1-888-993-5853)
Canada: 1-800-36-FLUKE (1-800-363-5853)
Europe: [phone]
Japan: [phone]
Singapore: [phone]
Anywhere in the world: [phone]
Address correspondence to:
Fluke Corporation Fluke Europe B.V.
P.O. Box 9090, P.O. Box 1186,
Everett, WA 98206-9090 5602 BD Eindhoven
USA The Netherlands
Visit us on the World Wide Web at: www.fluke.com

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2
Precautions and Safety Information
WWarning
If this product is used in a manner not specified by the
manufacturer, the protection provided by the equipment may
be impaired.
Read the “Safety Information” page before servicing this product.
In this manual, a Warning identifies conditions and actions that pose hazard(s) to the
user; a Caution identifies conditions and actions that may damage the Meter or the test
instruments.
International Symbols
International symbols used on the Meter and in this manual are explained in Table 1.
Table 1. International Symbols
Symbol Meaning Symbol Meaning
Alternating current Earth ground
Direct current Fuse
Alternating or direct current Conforms to European Union
directives
Refer to the manual. Important
information. Conforms to relevant Canadian Standards Association directives
Inspected and licensed by TÜV
Product Services. Double insulated
Battery Underwriters Laboratories, Inc.

True RMS Multimeter
Safety Information
3
Safety Information
WWarnings and Precautions
To avoid possible electric shock or personal injury, follow these guidelines:
•Do not use the Meter if it is damaged. Before you use the Meter, inspect the case.
Look for cracks or missing plastic. Pay particular attention to the insulation
surrounding the connectors.
•Inspect the test leads for damaged insulation or exposed metal. Check the test
leads for continuity. Replace damaged test leads before you use the Meter.
•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 the rated voltage, as marked on the Meter, between
terminals or between any terminal and earth ground.
•Before use, verify the Meter’s operation by measuring a known voltage.
•When measuring current, turn off circuit power before connecting the Meter in the
circuit. Remember to place the Meter in series with the circuit.
•When servicing the Meter, use only specified replacement parts.
•Use caution when working above 30 V ac rms, 42 V peak, or 60 V dc. Such
voltages pose a shock hazard.
•Avoid working alone.
•When using the probes, keep your fingers behind the finger guards on the probes.
•Connect the common test lead before you connect the live test lead. When you
disconnect test leads, disconnect the live test lead first.
•Remove test leads from the Meter before you open the battery door.
•Do not operate the Meter with the battery door or portions of the cover removed or
loosened.
•To avoid false readings, which could lead to possible electric shock or personal
injury, replace the batteries as soon as the low battery indicator (M) appears.
•Use only type AA batteries, properly installed in the Meter case, to power the
Meter.
Caution
To avoid possible damage to the Meter or to the equipment under test, follow these
guidelines:
•Disconnect circuit power and discharge all high-voltage capacitors before testing
resistance, continuity, diodes, or capacitance.
•Use the proper terminals, function, and range for your measurements.
•Before measuring current, check the Meter's fuses and turn power OFF to the
circuit before connecting the Meter to the circuit.

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Specifications
Accuracy
Accuracy is specified for a period of one year after calibration, at 18 °C to 28 °C (64 °F
to 82 °F), with relative humidity to 90 %. Accuracy specifications are given as:
±( [ % of reading ] + [ number of least significant digits ] )
AC mV, AC V, AC µA, AC mA, and AC A specifications are ac-coupled, true rms and are
valid from 5 % of range to 100 % of range. AC crest factor can be up to 3.0 at full-scale, 6.0
at half-scale, except the 3000 mV and 1000 V ranges where it is 1.5 at full scale, 3.0 at half-
scale.
Feature Summary
Feature Description
Dual Digital Displays
Analog Bar Graph
Primary: 50,000 counts
Secondary: 5,000 count
Bar graph: 51 segments, updates 40 times/second
Backlight with 2 brightness levels Bright white backlight for clear readings in poorly lighted areas
Fast Autorange Meter automatically selects best range - instantly
AC+DC true rms, ac rms specified
to 100 kHz Choices for AC only, AC and DC dual display, or AC+DC readings
dBm, dBV User selectable impedance references for dBm
AutoHOLD Holds readings on display
Continuity / Open test Beeper sounds for resistance readings below threshold, or to
indicate a momentary open circuit
Fast Bar Graph 51 segments for peaking and nulling
Duty cycle / Pulse width Measure signal on or off time in % or milliseconds
MIN MAX Mode
FAST MN MX with 24-hour time
stamp
Record maximum, minimum, and average values.
24-hour clock for MAX or MIN, elapsed time for AVG.
FAST MN MX captures peaks to 250 µsec.
Closed-Case Calibration No internal adjustments needed
Battery / Fuse Access Door Battery or fuse replaceable without voiding calibration
Hi-Impact Overmolded Case Protective holster features

True RMS Multimeter
Basic Specifications
5
Basic Specifications
Function Ranges/Description
DC Voltage 0 to 1000 V
AC Voltage, true RMS 2.5 mV to 1000 V – 100 kHz bandwidth
Basic Accuracy DC voltage: 0.025 %
AC voltage: 0.4 %
DC Current 0 to 10 A (20 A for 30 seconds)
AC Current, true RMS 25 µA to 10 A (20 A for 30 seconds)
Resistance 0 to 500 MΩ
Conductance 0 to 500 nS
Capacitance 0.001 nF to 50 mF
Diode Test 3.1 V
Temperature −200 °C to 1350 °C (−328 °F to 2462 °F)
Frequency 0.5 Hz to 1000 kHz
LOGGING Intervals
(Model 189 only) At least 288 intervals may be stored. Up to 700 unstable event values (see AutoHold) are automatically added to LOGGING memory for viewing only
through optional PC software. Additional intervals will be logged up to 995 if
the signal is stable.
SAVE Readings
(Model 189 only) Up to 100 readings may be saved by the user in a memory separate from LOGGING memory. These readings may be viewed using VIEW MEM.

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Detailed Accuracy Specifications
Accuracy is specified for a period of one year after calibration, at 18°C to 28 °C (64 °F
to 82 °F), with relative humidity to 90 %. Accuracy specifications are given as:
±( [ % of reading ] + [ number of least significant digits ] )
AC mV, AC V, AC µA, AC mA, and AC A specifications are ac coupled, true rms and
are valid from 5 % of range to
100 % of range. AC crest factor can be up to 3.0 at full-scale, 6.0 at half-scale except the
3000 mV and 1000 V ranges where it is 1.5 at full scale, 3.0 at half-scale.
Accuracy
Function Range Resolution 45 Hz- 1 kHz 20 Hz- 45 Hz 1 kHz- 10 kHz 10 kHz- 20 kHz 20 kHz- 100 kHz
AC mV 1, 2 50.000 mV 0.001 mV 0.4 % + 40 2 % + 80 5 % + 40 5.5 % + 40 15 % + 40
500.00 mV 0.01 mV 0.4 % + 40 2 % + 80 5 % + 40 5.5 % + 40 8 % + 40
3000.0 mV 0.1 mV 0.4 % + 40 2 % + 80 0.4 % + 40 1.5 % + 40 8 % + 40
AC V1, 2 5.0000 V 0.0001 V 0.4 % + 40 2 % + 80 0.4 % + 40 1.5 % + 40 8 % + 40
50.000 V 0.001 V 0.4 % + 40 2 % + 80 0.4 % + 40 1.5 % + 40 8 % + 40
500.00 V 0.01 V 0.4 % + 40 2 % + 80 0.4 % + 40 Not
specified Not specified
1000.0 V 0.1 V 0.4 % + 40 2 % + 80 0.4 % + 40 Not
specified Not specified
dBV −52 to −6 0.01 dB 0.1 dB 0.2 dB 0.5 dB 0.5 dB 1.4 dB
−6 to +34 0.01 dB 0.1 dB 0.2 dB 0.1 dB 0.2 dB 0.8 dB
+34 to +60 0.01 dB 0.1 dB 0.2 dB 0.1 dB Not
specified Not specified
1. For the 5,000 count mode, divide the number of least significant digits (counts) by 10.
2. A residual reading of 8 to 180 digits with leads shorted, will not affect stated accuracy above 5 % of range.
Accuracy
Function Range Resolution 45 Hz- 1 kHz 20 Hz- 45 Hz 1 kHz- 20 kHz 20 kHz- 100 kHz
AC µA 500.00 µA 0.01 µA 0.75 % + 20 1 % + 20 0.75 % + 20 6 % + 40
5,000.0 µA0.1µA 0.75 % + 5 1% + 5 0.75 % + 10 2 % + 40
AC mA 50.000 mA 0.001 mA 0.75 % + 20 1% + 20 0.75 % + 20 9 % + 40
400.00 mA 0.01 mA 0.75 % + 5 1% + 5 1.5 % + 10 4 % + 40
AC A 5.0000 A 0.0001 A 1.5 % + 20 1.5% + 20 6 % + 40 Not specified
10.000 A 10.001 A 1.5 % + 5 1.5% + 5 5 % + 10 Not specified
1. 10 A continuous up to 35 °C, less than 10 minutes 35 °C to 55 °C. 20 A overload for 30 seconds maximum.

True RMS Multimeter
Detailed Accuracy Specifications
7
Accuracy Accuracy Dual Display AC or AC+DC 3
Function Range Resolution DC 20 Hz- 45 Hz 45 Hz - 1 kHz 1 kHz- 20 kHz
DC mV 50.000 mV 0.001 mV 0.1% + 20 6 % + 40
500.00 mV 0.01 mV 0.03 % + 2
3000.0 mV 0.1 mV 0.025 % + 5 2 % + 40
DC V 5.0000 V 0.0001 V 0.025 % + 10 2
50.000 V 0.001 V 0.03 % + 3 2
500.00 V 0.01 V 0.1 % + 2 2Not specified
1000.0 V 0.1 V 0.1 % + 2 2
2 % + 80 0.5 % + 40
Not specified
DC µA 500.00 µA 0.01 µA 0.25 % + 20 1 % + 20 1.0 % + 20 2 % + 40
5,000 µA0.1µA 0.25 % + 2 1 % + 10 0.75 % + 10 2 % + 40
DC mA 50.000 mA 0.001 mA 0.15 % + 10 1 % + 20 0.75 % + 20 2 % + 40
400.00 mA 0.01 mA 0.15 % + 2 1 % + 10 1 % + 10 3 % + 40
DC A 5.0000 A 0.0001 A 0.5 %+ 10 2 % + 20 2 % + 20 6 % + 40
10.000 A 10.001 A 0.5 %+ 2 1.5 % + 10 1.5 % + 10 5 % + 10
1. 10 A continuous up to 35 °C, less than 10 minutes 35 °C to 55 °C. 20 A overload for 30 seconds maximum.
2. 20 counts in dual display DC or AC+DC.
3. See AC conversions notes for AC mV and V
Function Range Resolution Accuracy
Resistance 1500.00 Ω0.01 Ω0.05 % + 10 3
5.0000 kΩ0.0001 kΩ0.05 % + 2
50.000 kΩ0.001 kΩ0.05 % + 2
500.00 kΩ0.01 kΩ0.05 % + 2
5.0000 MΩ0.0001 MΩ0.15 % + 4 2
30.000 MΩ0.001 MΩ1 % + 4 2
100.0 MΩ0.1 MΩ3 % + 2 4
500.0 MΩ0.1 MΩ10 % + 2 4
Conductance 50.00 nS 0.01 nS 1 % + 10
1. For the 5,000 count mode, divide the number of least significant digits (counts) by 10.
2. For relative humidity greater than 70 %, resistance accuracy is 0.5 % over 1 MΩand 2.5 % over 10 MΩ.
3. Using relative mode (REL ∆) to zero residual reading.
4. To ensure stated accuracy, switch to conductance mode and verify that the open circuit reading is less than
0.10 nS.

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Function Ranges Resolution Accuracy
Capacitance 21.000 nF 0.001 nF 2% + 5
10.00 nF 0.01 nF 1 % + 5
100.0 nF 0.1 nF
1.000 µF 0.001 µF
10.00 µF 0.01 µF
100.0 µF 0.1 µF
1,000 µF 1 µF
10.0 mF 0.01 mF
50.00 mF 0.01 mF 33 % + 10
Diode Test 13.1000 V 0.0001 V 2 % + 20
1. For the 5,000 count mode, divide the number of least significant digits (counts) by 10.
2. For film capacitor or better, using Relative mode (REL ∆) to zero residual on 1.000 nF and 10.00 nF ranges.
3. Least significant digit not active above 10 mF.
Function Range Resolution Accuracy
Frequency 500.00 Hz 0.01 Hz 1±(0.0050 % + 1)
5.0000 kHz 0.0001 kHz
50.000 kHz 0.001 kHz
999.99 kHz 0.01 kHz
Duty Cycle 10.00% to 90.00 % 0.01 % ±((voltage range/input voltage) X 300
counts) 5,6
Pulse Width 499.99 ms 0.01 ms ±(3 % X (voltage range/input voltage) + 1
count)5,6
999.9 ms 0.1 ms
Temperature −200 to +1350 °C0.1°C±( 1% of reading + 1 °C) 2,3
−328 to +2462 °F0.1°F±( 1% of reading + 1.8 °F) 2,3
MIN MAX
AVG Response: 100 ms to 80 % Specified accuracy ±12 counts for changes > 200 ms in duration. (±40
counts in AC for changes > 350 ms and
inputs > 25 % of range)
FAST MN MX 250 µs 4Specified accuracy ±100 counts up to
5,000 count (full range) reading. For higher
peak readings (to 20,000 counts),
specified accuracy ±2% of reading.
1. Reading will be 0.00 for signals below 0.5 Hz.
2. Accuracy specification is relative to the user-adjustable temperature offset, and assumes ambient temperature
stable to ±1 °C.
3. For ambient temperature changes of ±5 °C, rated accuracy applies after 1 hour.
4. For repetitive peaks; 2.5 ms for single events. Use DC function settings below 20 Hz. 50 mV range not specified.
5. Frequency greater than 5 Hz, except for VDC, 500 mVDC and 3000 mVDC functions; 0.5 Hz to 1 kHz. Signals
centered around trigger levels.
6. Range/input ratios also apply to current functions. 500 counts or 5 % for 10 A ranges.

True RMS Multimeter
Frequency Counter Sensitivity
9
Frequency Counter Sensitivity
Approximate VAC
Sensitivity (RMS Sine
Wave)1
Input
Range 15 Hz -
100 kHz 2500 kHz 2VAC
Bandwidth 3
Approximate
VDC Trigger
Levels 1VDC Bandwidth 3
50 mV 5 mV 10 mV 1 MHz -5 mV & 5 mV 1 MHz
500 mV 20 mV 20 mV 1 MHz 5 mV & 65 mV 1 MHz
3000 mV 500 mV 2000 mV 800 kHz 140 mV & 200 mV 90 kHz
5 V 0.5 V 2.0 V 950 kHz 1.4 V & 2.0 V 14 kHz
50 V 5 V 5.0 V 1 MHz 0.5 V & 6.5 V > 400 kHz
500 V 20 V 20 V 1 MHz 5 V & 65 V > 400 kHz
1000 V 100 V 100 V > 400 kHz 5 V & 65 V > 400 kHz
1. Maximum input = 10 x Range (1000 V max). Noise at low frequencies and amplitudes may affect accuracy.
2. Useable at reduced sensitivity to 0.5 Hz and 1000 kHz.
3. Typical frequency bandwidth with full scale (or maximum 2 X 107V-Hz product) RMS sine wave.
Burden Voltage (A, mA, µA)
Function Range Burden Voltage (typical)
mA - µA 500.00 µA102 µV / µA
5,000 µA 102 µV / µA
50.000 mA 1.8 mV / mA
400.00 mA 1.8 mV / mA
A 5.0000 A 0.04 V / A
10.000 A 0.04 V / A
Input Characteristics
Function Input Impedance (Nominal)
Volts, mV 10 MΩ, < 100 pF
Common Mode Rejection Ratio Normal Mode Rejection
DC Volts, mV >100 dB at dc, 50 Hz or 60 Hz ±0.1% >90 dB at 50 Hz or 60 Hz ±0.1%
AC Volts, mV > 90 dB dc to 60 Hz
Full-Scale Voltage
Open Circuit Test Voltage To 5 MΩ30 MΩ+ nS
Ohms < 5 V 500 mV 3.1 V
Diode Test < 5 V 3.1000 V
Typical Short-Circuit Current
500 Ω5 kΩ50 kΩ500 kΩ5 MΩ30 MΩ
Ohms 1 mA 100 µA10 µA1µA0.1 µA0.1 µA
Diode Test 1 mA typical

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Required Equipment
Required equipment is listed in Table 2. 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 2. Required Equipment
Equipment Required Characteristics Recommended Model
Calibrator AC Voltage Range: 0-1000 Vac
Accuracy: + 0.1 %
Frequency Range: 20 Hz – 100 kHz
Accuracy: +3 %
DC Voltage Range: 0-1000 Vdc
Accuracy: + 0.006 %
Current Range: 0-10A
Accuracy: AC mA - +0.18 %
AC A - + 0.38 %
Frequency range: 1 kHz – 20 kHz
DC mA - + 0.06 %
DC A - + 0.125 %
Frequency Source: 500 Hz-20 kHz
Accuracy: + 0.00125 %
Amplitude: 1 Volt
Accuracy: + 5 %
Ohms Range: 0 Ω- 50 MΩ
Accuracy: + 0.0125 %
Capacitance Range: 110.0 nF & 11.00
µF
Accuracy: +0.25%
Temperature Range: -10 to 350 °C
Accuracy: 0.3%
Fluke 5520A
Thermocouple Adapter
Accessory K-type Fluke 80AK
K-type Thermocouple K-type, mini-plug on both ends N/A
Serial Cable, Infrared Fluke P/N 1578406
87/89-IV, 187/189
Service Software Fluke P/N 676152
IR Cable Adapter Fluke P/N 1576688

True RMS Multimeter
Basic Maintenance
11
Basic Maintenance
WWarning
To avoid electrical shock or personal injury, remove the test
leads and any input signals before opening the case or
replacing the battery or fuses. To prevent damage or injury,
install ONLY batteries or fuses specified for this product.
Opening the Meter Case
Caution
To avoid unintended circuit shorting, always place the
uncovered Meter assembly on a protective surface. When the
case of the Meter is open, circuit connections are exposed.
To open the Meter case, do the following:
1. Disconnect test leads from any live source, turn the rotary switch to OFF, and
remove the test leads from the front terminals.
2. Remove the battery door by using a flat-blade screwdriver to turn the battery door
fasteners 1/4-turn counterclockwise.
3. The case bottom is secured to the case top by four screws, one at each corner.
Remove the screws with a Phillips-head screwdriver.
4. Pull the two halves of the case apart.
Removing and Reinserting the Circuit Board Assembly
The circuit board assembly must be removed to access and replace the LCD.
Caution
The circuit board is extremely susceptible to contamination.
Handle it by the input receptacle, fuse clips or edges of the
board only. You can use clean surgical gloves to help avoid
contamination.
1. Open the Meter case and remove the case bottom to access the circuit board.
2. Remove the two Phillips-head screws securing the circuit board to the case top and
lift it out carefully to avoid contamination.
3. To reinsert the circuit board, simply place it into the case top with the LCD display
showing through the window.
4. Carefully replace the two Phillips-head screws that connect the circuit board to the
case top.
Caution
Do not over-torque the two Phillips-head screws when you
reconnect the circuit board to the case top. Doing so may
create shielding problems and cause the Meter to give incorrect
readings.

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Replacing the LCD
If you need to replace the LCD, you will find it easier to leave the LCD assembly
attached to the circuit board and access the LCD by removing the LCD mask from the
front of the LCD assembly.
1. Remove the circuit board as described under “Removing and Reinserting the Circuit
Board Assembly.”
2. Carefully insert the tip of a thin screwdriver under the LCD mask at the top of the
display as shown in Figure 1.
LCD
LCD Mask
aau05f.eps
Figure 1. Removing LCD Mask to Access LCD
3. Lift up the LCD mask gently with the screwdriver blade to loosen the mask from the
assembly. Be careful to press upward, not inward toward the LCD. By hand, tilt the
LCD mask upward to release.
4. Replace the LCD. The LCD must be centered on the platform between the brackets
before you replace the LCD mask. If the LCD is improperly aligned, the display may
show missing segments or meaningless readings.
5. Reattach the LCD mask by pressing it over the LCD until it snaps into place.