380580-en-US_v2.6 6/20
5
Measurement Principles
The test current flows through the resistance from the
(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:
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.
C+
C-
P+
P-
Current
Volts
www.
GlobalTestSupply
.com
Find Quality Products Online at:
