Extech Instruments 380460 User manual

User's Guide
Precision Milliohm Meters
Models 380460 and 380462
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.
Test Equipment Depot - 800.517.8431 - 99 Washington Street Melrose, MA 02176
FAX [phone] - TestEquipmentDepot.com
99 Washington Street
Melrose, MA 02176
Phone [phone]
Toll Free 1-800-517-8431
Visit us at www.TestEquipmentDepot.com
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Model 380460 and 380462 Version 2.1 March 2005
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Specifications
General Specifications
Circuit Custom one-chip LSI microprocessor circuit
Display 0.7" (18 mm) LCD with 2000 display counts
Measurement terminals 4-Terminal Kelvin type
Measurement ranges Five (5) ranges (200m, 2, 20, 200, 2000Ωohms)
Zero Adjust ±50 count adjustment
Sampling Time Approximately 0.4 seconds
Over input indication Indication of "1 - - -"
Operating Temperature 32 °F to 122 °F (0 °C to 50 °C)
Operating Humidity 80% Relative Humidity max.
Power Supply 110V (380460) or 220V (380462) ±15%, 50/60Hz
Power Consumption Less than 2 VA
Weight 1.32 lbs (600g)
Dimensions 6.3 x 4.72 x 3.35" (160 x 120 x 85 mm) with cover
Accessories Power Cable and 4-wire Kelvin clip leads
Range Specifications
Range Resolution
Test
Current Accuracy
Open Circuit
Voltage
200 mΩ0.1mΩ100mA ± 0.75% + 4 digits 3.8V
2 Ω1mΩ10mA ± 0.75% + 2 digits 3.4V
20 Ω10mΩ10mA ± 0.75% + 2 digits 3.4V
200 Ω0.1 Ω1mA ± 0.75% + 2 digits 3.2V
2000 Ω1 Ω1mA ± 0.75% + 2 digits 3.2V
Note: Specifications tested using RF Field Strength <3V/m and frequency <30MHz

Model 380460 and 380462 Version 2.1 March 2005
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Meter Description
1. LCD Display
2. Zero adjust knob
3. Range Dial
4. Power switch
5. 200mΩselect switch
6. AC power cord
7. Kelvin lead to meter connections
8. Carrying case
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 HI Rx1 Rx2
White
bands
Rx
Device under test
To Meter

Model 380460 and 380462 Version 2.1 March 2005
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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
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 200m range to prepare for zeroing. Ensure that
200m is selected on the 200m select switch.
2. Perform a Zero Adjustment per the following:
•Short the Kelvin Clips as shown in the diagram below.
•Rotate the Zero Adjust Knob until the meter indicates zero units.
3. Select the desired measuring range via the rotary Range select switch. When using the
200m range, put the 200m select switch to the 200m position; for all other
measurements put this switch in the opposite position.
4. Either clip the leads onto a component or clip the leads between two points in a circuit.
5. Observe the meter reading.
Test Equipment Depot - 800.517.8431 - 99 Washington Street Melrose, MA 02176
FAX [phone] - TestEquipmentDepot.com