Calibration Manual
36 Pages
Preview
Page 1
®
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 P.O. Box 9090 Everett, WA 98206-9090 U.S.A. 11/99
Fluke Europe B.V. P.O. Box 1186 5602 BD Eindhoven The Netherlands
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 i
187/189 Calibration Manual
Remote Interface ... 25 Temperature Calibration ... 25 Setup ... 25 Procedure ... 26 Re-Programming Serial Number or Model Number... 26 Parts and Accessories ... 27
ii
List of Tables
Table 1. 2. 3. 4. 5.
Title
Page
International Symbols ... 2 Required Tools and Equipment ... 10 Temperature Test Input and Display ... 17 Performance Test Steps ... 18 Calibration Inputs ... 23
iii
187/189 Calibration Manual
iv
List of Figures
Figure 1. 2. 3. 4. 5. 6. 7.
Title
Page
Removing LCD Mask to Access LCD... 12 Testing the Current Fuses ... 14 Battery and Fuse Replacement ... 15 Display Test ... 16 Locating Recessed Calibration Button ... 21 Calibration Display... 22 Replacement Parts and Accessories... 28
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187/189 Calibration Manual
vi
Introduction W Warning 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: +31 402-678-200 Japan: +81-3-3434-0181 Singapore: +65-738-5655 Anywhere in the world: +1-425-446-5500 Address correspondence to: Fluke Corporation P.O. Box 9090, Everett, WA 98206-9090 USA
Fluke Europe B.V. P.O. Box 1186, 5602 BD Eindhoven The Netherlands
Visit us on the World Wide Web at: www.fluke.com 1
187/189 Calibration Manual
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
2
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
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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187/189 Calibration Manual
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 halfscale.
Feature Summary Feature Dual Digital Displays
4
Description
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
Record maximum, minimum, and average values. 24-hour clock for MAX or MIN, elapsed time for AVG.
FAST MN MX with 24-hour time stamp
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
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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187/189 Calibration Manual
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 AC mV
AC V
1, 2
1, 2
dBV
Range
Resolution
45 Hz1 kHz
20 Hz45 Hz
1 kHz10 kHz
10 kHz20 kHz
20 kHz100 kHz
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
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
−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 45 Hz1 kHz
20 Hz45 Hz
1 kHz20 kHz
0.01 µA
0.75 % + 20
1 % + 20
0.75 % + 20
6 % + 40
5,000.0 µA
0.1 µA
0.75 % + 5
1% + 5
0.75 % + 10
2 % + 40
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
5.0000 A
0.0001 A
1.5 % + 20
1.5% + 20
6 % + 40
Not specified
0.001 A
1.5 % + 5
1.5% + 5
5 % + 10
Not specified
Function
Range
AC µA
500.00 µA
AC mA
AC A
10.000 A
1
Resolution
20 kHz100 kHz
1. 10 A continuous up to 35 °C, less than 10 minutes 35 °C to 55 °C. 20 A overload for 30 seconds maximum.
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True RMS Multimeter Detailed Accuracy Specifications
Accuracy
Accuracy Dual Display AC or AC+DC
3
Function
Range
Resolution
DC
20 Hz45 Hz
45 Hz 1 kHz
1 kHz20 kHz
DC mV
50.000 mV
0.001 mV
0.1% + 20
2 % + 80
0.5 % + 40
6 % + 40
500.00 mV
0.01 mV
0.03 % + 2
3000.0 mV
0.1 mV
0.025 % + 5
DC V
DC µA
DC mA
2 % + 40 2
5.0000 V
0.0001 V
0.025 % + 10
50.000 V
0.001 V
0.03 % + 3
500.00 V
0.01 V
0.1 % + 2
2
Not specified
2
Not specified
2
1000.0 V
0.1 V
0.1 % + 2
500.00 µA
0.01 µA
0.25 % + 20
1 % + 20
1.0 % + 20
2 % + 40
5,000 µA
0.1 µA
0.25 % + 2
1 % + 10
0.75 % + 10
2 % + 40
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
5.0000 A
0.0001 A
0.5 %+ 10
2 % + 20
2 % + 20
6 % + 40
0.001 A
0.5 %+ 2
1.5 % + 10
1.5 % + 10
5 % + 10
DC A
10.000 A
1
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 Resistance
1
Conductance
Range
Resolution
Accuracy
500.00 Ω
0.01 Ω
0.05 % + 10
5.0000 kΩ
0.0001 kΩ
0.05 % + 2
50.000 kΩ
0.001 kΩ
0.05 % + 2
500.00 kΩ
0.01 kΩ
0.05 % + 2
5.0000 MΩ
0.0001 MΩ
0.15 % + 4
30.000 MΩ
0.001 MΩ
1%+4
2
100.0 MΩ
0.1 MΩ
3%+2
4
500.0 MΩ
0.1 MΩ
10 % + 2
50.00 nS
0.01 nS
1 % + 10
3
2
4
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 MΩ and 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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187/189 Calibration Manual
Function Capacitance
Diode Test
Ranges
2
1
Resolution
Accuracy
1.000 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
3
3 % + 10
3.1000 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 Frequency
Range
Resolution 1
Accuracy ± (0.0050 % + 1)
500.00 Hz
0.01 Hz
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 5,6 counts)
Pulse Width
499.99 ms
0.01 ms
± (3 % X (voltage range/input voltage) + 1 5,6 count)
999.9 ms
0.1 ms
−200 to +1350 °C
0.1 °C
± ( 1% of reading + 1 °C)
−328 to +2462 °F
0.1 °F
± ( 1% of reading + 1.8 °F)
Temperature
2,3
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
Specified accuracy ±100 counts up to 5,000 count (full range) reading. For higher peak readings (to 20,000 counts), specified accuracy ± 2% of reading.
4
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.
8
True RMS Multimeter Frequency Counter Sensitivity
Frequency Counter Sensitivity Input Range
Approximate VAC Sensitivity (RMS Sine 1 Wave) 15 Hz 2 2 100 kHz 500 kHz
VAC 3 Bandwidth
Approximate VDC Trigger 1 Levels
VDC Bandwidth
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
5V
0.5 V
2.0 V
950 kHz
1.4 V & 2.0 V
14 kHz
50 V
5V
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
3
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 107 V-Hz product) RMS sine wave.
Burden Voltage (A, mA, µA) Function
Range
mA - µA
Burden Voltage (typical)
500.00 µA
A
102 µV / µA
5,000 µA
102 µV / µA
50.000 mA
1.8 mV / mA
400.00 mA
1.8 mV / mA
5.0000 A
0.04 V / A
10.000 A
0.04 V / A
Input Characteristics Function
Input Impedance (Nominal)
Volts, mV
DC Volts, mV
10 MΩ, < 100 pF Common Mode Rejection Ratio
Normal Mode Rejection
>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 MΩ
30 MΩ + nS
Ohms
<5V
500 mV
3.1 V
Diode Test
<5V
3.1000 V
Typical Short-Circuit Current
Ohms Diode Test
500 Ω
5 kΩ
50 kΩ
500 kΩ
5 MΩ
30 MΩ
1 mA
100 µA
10 µA
1 µA
0.1 µA
0.1 µA
1 mA typical
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187/189 Calibration Manual
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 Calibrator
Required Characteristics AC Voltage Range: 0-1000 Vac Accuracy: + 0.1 % Frequency Range: 20 Hz – 100 kHz Accuracy: +3 %
Recommended Model Fluke 5520A
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: µF Accuracy: +0.25%
110.0 nF & 11.00
Temperature Range: -10 to 350 °C Accuracy: 0.3%
10
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
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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187/189 Calibration Manual
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 Mask
LCD
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.
12