Micro-Ohmmeter Model 5600
Very Low Resistance
When measuring very low resistive values (2000µΩ range) the presence
of stray DC currents may affect the accuracy of the measurements.
These currents can be present due to a variety of reasons including
chemical or thermal EMF in samples made of dissimilar metals. You can
eliminate the effects of this by reversing the direction of current flow
(inverter switch, see Figure 6) and using the average of forward and
reverse readings. A minus sign will appear in the display when the switch
is in the reverse position. Disregard this sign when calculating the
average values.
The presence of AC interference in the sample under test may cause the
measured value on the display to fluctuate. This interference may
become more noticeable in the presence of strong electric fields. The
effects of this interference may be reduced by twisting the leads
together.
+ I
– I
Figure 6
Meter Readings
When testing resistive samples, the meter reading will stabilize within the
first few seconds. On inductive loads (e.g. transformers), the
measurement reading may take from several seconds to a few minutes
to stabilize and depends greatly on the type of equipment and the
impedance of the equipment under test. On very large samples such as
utility transformers, 10 to 15 minutes charging time may be necessary.
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