Precision Milliohm Meters
Models 380460 and 380462
User Guide
Introduction
Congratulations on your purchase of the Extech Milliohm Meter Model 380460 (110V) or Model
380462 (220V). The milliohm meters are enclosed in rugged carrying cases for durability.
Measurements are made with Kelvin test leads (supplied) for optimal accuracy in five (5) selectable ranges. Careful use of this meter will provide years of reliable service.
Meter Description
2. Zero adjust knob
7 6
8
5. 200m select switch
6. AC power cord
7. Kelvin lead to meter connections
1
2 4
3 5
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Operation
Basic Principles of 4-wire Measurements
For each range, the meter provides a specific amount of test current (refer to General Specifications) which flows from the HI to the LO meter terminal and therefore from the HI to the LO clip lead (Refer to the diagram). This is the current that ultimately passes through the device under test (RX in diagram below).
Once the test current is applied to the device under test, clip leads Rx1 & Rx2 measure the voltage drop across the device under test. The following equations detail how the meter accomplishes its measurement tasks.
LO Rx1
To Meter
White bands
Rx2 HI
Rx
Device under test
Measurement Equations
Vx = Is x Rx;
Where Vx is the voltage (measured by the meter) across the device under test; Is is the test current;
Rx is the resistance of the device under test. From Vx = Is x Rx, the meter moves to the next step which is: Rx = Vx/Is. With this equation the meter determines the resistance of the device under test.
Note that the measured resistance (Rx1 & Rx2) is not affected by stray resistance since the test current is supplied directly to the device under test. This is the advantage of the 4-wire Kelvin lead configuration over 2-wire methods which introduce errors into low resistance measurements.
International Symbols
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Powering the Meter
Connect the meter to the correct power source (110 or 220VAC); the Model 380460 uses 110VAC and the Model 380462 uses 220VAC (note that these meters are NOT interchangeable). Do not apply voltage to the meter input measurement terminals. Meter damage may result.
Measurement Procedure
1. Rotate the Range select switch to the desired range.
2. When using the 200m range, put the 200m select switch to the 200m position; for all other measurement ranges put this switch in the opposite position
3. Perform a Zero Adjustment per the following:
Short the Kelvin Clips as shown in the diagram below.
(Make sure that the clips are clean)
Rotate the Zero Adjust Knob until the meter indicates zero units.
4. Either attach the test leads onto a component or attach the leads between two points on a circuit.
5. Observe the meter reading.
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Specifications
General Specifications
Circuit
Display
Measurement terminals
Measurement ranges
Zero Adjust
Sampling Time
Over range indication
Operating Temperature
Operating Humidity
Power Supply
Power Consumption
Weight
Dimensions
Accessories
Custom one-chip LSI microprocessor circuit
18 mm (0.7") LCD with 2000 display counts
4-Terminal Kelvin type
Five (5) ranges (200m, 2, 20, 200, 2000 ohms)
±50 count adjustment
Approximately 0.4 seconds
Indication of "1 "
0 °C to 50 °C (32 °F to 122 °F)
80% Relative Humidity max.
110V (380460) or 220V (380462) ±15%, 50/60Hz
Less than 2 VA
694g (1.53 lbs.)
167 x 122 x 85 mm (6.6 x 4.8 x 3.4") with cover
Power Cable and 4-wire Kelvin clip leads(380465)
Range Specifications
Range
200 m
2
20
Resolution
0.1m
1m
10m
Test
Current
100mA
10mA
10mA
Accuracy
± 0.75% + 4 digits
± 0.75% + 2 digits
± 0.75% + 2 digits
Open Circuit
Voltage
4.4V
3.6V
3.6V
200
2000
0.1
1
1mA
1mA
± 0.75% + 2 digits
± 0.75% + 2 digits
3.5V
3.5V
Note: Specifications tested using RF Field Strength <3V/m and frequency <30MHz
Copyright © 2013-2015 FLIR Systems, Inc.
All rights reserved including the right of reproduction in whole or in part in any form.
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