USER GUIDE
Model 380580
Battery Powered Milliohm Meter
Introduction
Congratulations on your purchase of Extech’s Model 380580 Battery Powered Milliohm Meter. This
device offers five resistance ranges with resolution as low as 0.1m. The 4-wire Kelvin clip connection
ensures optimum accuracy. Typical applications include transformer, motor coil, and PC Board
resistance measurements. This professional meter, with proper care, will provide years of safe reliable
service.
Meter Description
1.
2.
3.
4.
5.
6.
Current Terminals
Potential Measurement Terminals
LCD Display
Start/Stop Test Button
Range Select/Power Switch
LED Error Lights
• No Test/Over Temperature
• R
P
Voltage Regulation
• R
C
Current Regulation
Current/Range Table
7.
Leads
Current Leads- Banana plug to alligator clip
C1- Green
C2- Blue
Voltage Potential Leads- Banana plug to alligator clip
P1- Red
P2- Black
Kelvin Clips- Banana Plugs (2) to Kelvin Clip
Red (P1) Green (C1)
Black (P2) and Blue (C2)
Measurement Considerations
1.
2.
3.
4.
5.
6.
7.
8.
9.
Do not apply voltage to the meter input terminals. Meter damage may result.
Always insure that the circuit to be measured is switched OFF, isolated and completely de-
energized before connecting the test leads.
If the Over Temperature LED (NO TEST) indicator is lit, allow the instrument to cool down
before proceeding further.
The R
C
led indicates when the test current falls out of regulation. Selecting a higher range
may eliminate the condition.
The R
P
led indicates when the voltage on the device under test is too high. Selecting a lower
range may eliminate the condition.
If either the R
C
or R
P
led is on, the measurement may be in error.
The current terminals are fuse protected.
Keep the potential test leads as short as possible. Long leads may introduce noise.
When using the four separate alligator clip leads always place the current leads outside the
potential leads.
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Preliminary Checks
Current Regulation Check
1. Connect the current leads C
1
and C
2
to the meter.
2. Set the function switch to the 200.0mΩ range.
3. Momentarily press the
TEST R
P
button. The meter will
intermittently beep and R
C
will light
4. Short the current leads C
1
to C
2.
5. The R
C
LED should go off, indicating that the meter is
operating correctly.
6. Momentarily press the
TEST R
P
button to stop the test
7. The meter will return to
NO TEST
status.
Voltage Measurement check
1. With the current test leads C
1
and C
2
shorted, connect and
short the potential (voltage) leads P
1
and P
2
.
2. Set the Function switch to the 200.0mΩ position. The
NO
TEST
status LED will light.
3. Momentarily press the
TEST R
P
button. (the meter will
intermittently beep)
4. The display should indicate 00.0
5. Momentarily press the
TEST R
P
button to stop the test.
The
NO TEST
status LED will light.
6. Remove the shorts from P
1
and P
2
, and C
1
and C
2
and
7. Short the test leads P
1
to C
1
and P
2
to C
2
8. The R
P
LED as well as the
NO TEST
status LED should
light indicating an over-voltage or over-range
9. Turn the rotary selector switch to OFF
Polarity check
1. Short the test leads P
1
to C
2
and P
2
to C
1
together.
2. Set the Function switch to the 200.0mΩ position.
3. The “-1“ negative indicator should appear in the display.
Operation check
Use the Kelvin clips for this test
1. Short the all the leads (P
1
, P
2
,C
2
,C
1
) together.
The P
1
,
P
2
,C
2
,C
1
order is important.
2. Set the Function switch to the 200.0mΩ position. The
NO TEST
status LED will light.
3. Momentarily press the
TEST R
P
button. (the meter will
intermittently beep
4. The display should indicate near 00.0 (+/-0.2mΩ)
depending on the test clip connections and both R
P
and R
C
LEDs should remain off.
5. Momentarily press the
TEST R
P
button to stop the test.
Note:
These tests can be performed on any range.
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Measurement Procedure
1.
2.
Select the desired measuring range on the meter. If the resistance of the device is unknown,
start with the highest range and work downward.
Clip the test leads onto the device under test. Note: When using the 4-wire/4 alligator clip
test leads, it is recommended that the current test leads be outside of the potential test leads
(as shown in the diagram below).
For a short test duration of 10 seconds, press the TEST R
P
button for less than 2 seconds.
This EnerSave™ feature can be used to conserve battery power.
For a long test duration of 60 seconds, press the TEST R
P
button for more than 3 seconds.
During the test, the meter will intermittently beep. At the end of the test or if the test is
stopped, “HOLD” will appear and the last reading will be “frozen” on the display.
3.
4.
5.
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Measurement Principles
The test current flows through the resistance from the
Current+ (C+)
terminal to the
Current - (C-)
terminal. The
P+
and
P-
(POTENTIAL) terminals measure the voltage drop across the device under
test only, thus eliminating the lead and contact resistances. The meter displays the resistance
based on the test current and the measured voltage; refer to the equation below:
P+
Volts
P-
C+
Current
C-
Rx = Vx / Is
Where:
Vx
is the voltage drop across the device under test;
Is
is the test current;
Rx
is the resistance of the device under test.
Thermal Effects
Temperature can have a significant effect on the performance of milliohmeter due to the temperature
coefficient of the resistance under test and thermal EMF’s across dissimilar conductors.
Most conductors have a large temperature coefficient of resistance
For example: 0.4%/°C for copper. A copper conductor that has a resistance of 10.00m ohm at 20°C
will increase to 10.40m ohm at 30°C. This should be taken into account..
A current going through a resistance will also elevate the temperature so duration of the test can also
change the resistance.
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