5. Applications
The PeakTech
®
2705 Digital Milli-Ohmmeter is suitable for a wide
range of applications such as:
* Measuring the winding resistance of electric motors, generators
and transformers.
* Bond testing in aircraft, railway, ships, domestic and industrial
wiring installations.
* Measuring the ring mains continuity testing in industrial and
domestic wiring installations.
* Measuring resistance in electronic equipment such as shunts,
PCB tracks, switch and relay resistance.
* Checking compression joints on overheads lines.
* Testing and maintenance of switchboard/sub-stations
equipment on such items as fuses, joints, contacts and bonds.
Thermal Effects
Temperature can have a significant effect on the performance of a
Digital Milli-Ohmmeter, due to the temperature coefficient of the
resistance under test and thermal EMF´s across the 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 10.00 mOhm at 20°C will increase to 10.40 mΩ at
30°C. This change should be taken into account, when making
measurements.
A current going through a resistance will also elevate its
temperature. So duration of the test can change the resistance.
When measuring the resistance of item, such as current shunts,
which have joints of dissimilar conductors, thermal EMF can affect
the accuracy of the measurement. This condition can be detected if
the reading altes, when the leads are reversed. To compensate for
this effect, the average of the two readings should be taken as the
true measurement.
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