How to measure insulation resistance

How to measure insulation resistance

For measurement of insulation resistance use the megohm meter. Clean isolation and remove from it residual charge grounding. Check the megohm meter, closing its wires then connect its contacts to the device and take readings of insulation resistance. In certain cases it is possible to use the voltmeter with big internal resistance

It is required to you

  • megohm meter, voltmeter


1. Disconnect the tested object from sources of electric current. After cleaning of isolation of dirt ground object to remove from it residual charge. Depending on the operating voltage of the device choose the equipment calculated on 1000, or 2500 V. For test of the device make sure that at the opened wires it shows infinity, and at shortly closed 0. For the device use wires with big insulation resistance which is not less than 10 megohms. Ground current carrying cables of the device on which measurement will be performed.

2. Attach device clips to conducting cables of the device or network and begin to rotate the generator for obtaining steady tension. To reach it, rotate the handle of the hand generator with frequency of 2 revolutions per second. For some time instrument readings will accrue therefore give tension within 1 minute when instrument readings stabilize.

3. That indications of the megohm meter were not influenced by leakage current on insulating surface, the device is connected with the special shielding clip. Then this current is taken away directly to the earth, passing the device.

4. Pay attention that measurements need to be made at temperature not below +5 degrees Celsius. The unstable humidity at lower temperatures does not allow to receive true indications of insulation resistance.

5. Working with the megohm meter, surely use clips with the isolated handles. If tension on the device exceeds 1 kV, in addition put on dielectric gloves. Do not touch when carrying out test current carrying parts of the device.

6. At insulation resistance research on direct current generators or accumulators, use voltmeters with internal resistance of 30-50 kOhm. For this purpose measure tension between source poles, then between each of poles and the earth.

Author: «MirrorInfo» Dream Team