Extech Instruments 380460 User manual

User Guide
Precision Milliohm Meters
Models 380460 and 380462

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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
1. LCD Display
2. Zero adjust knob
3. Range Dial
4. Power switch
5. 200mselect switch
6. AC power cord
7. Kelvin lead to meter connections
8. Carrying case

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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.
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
LO HI Rx1 Rx2
White
bands
Rx
Device under test
To Meter

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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 Custom one-chip LSI microprocessor circuit
Display 18 mm (0.7") LCD with 2000 display counts
Measurement terminals 4-Terminal Kelvin type
Measurement ranges Five (5) ranges (200m, 2, 20, 200, 2000ohms)
Zero Adjust ±50 count adjustment
Sampling Time Approximately 0.4 seconds
Over range indication Indication of "1 "
Operating Temperature 0 °C to 50 °C (32 °F to 122 °F)
Operating Humidity 80% Relative Humidity max.
Power Supply 110V (380460) or 220V (380462) ±15%, 50/60Hz
Power Consumption Less than 2 VA
Weight 694g (1.53 lbs.)
Dimensions 167 x 122 x 85 mm (6.6 x 4.8 x 3.4") with cover
Accessories Power Cable and 4-wire Kelvin clip leads(380465)
Range Specifications
Range Resolution
Test
Current Accuracy
Open Circuit
Voltage
200 m0.1m100mA ± 0.75% + 4 digits 4.4V
2 1m10mA ± 0.75% + 2 digits 3.6V
20 10m10mA ± 0.75% + 2 digits 3.6V
200 0.1 1mA ± 0.75% + 2 digits 3.5V
2000 1 1mA ± 0.75% + 2 digits 3.5V
Note: Specifications tested using RF Field Strength <3V/m and frequency <30MHz
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