Insulation resistance testers (also called insulation meters) can be used to perform three different types of insulation resistance tests, namely short-term or point reading, hourly resistance and dielectric absorption rate. Each test changes with the results and is used for a specific purpose.

To help you better understand what each test is and how to use an insulation resistance tester to test. We have created a brief guide below.

Three types of resistance test

Short-term or field reading test

Simply put the insulation resistance tester across the insulation layer to be tested to perform short-time or point-reading tests. Then operate it for a short period of time (usually 60 seconds). During this test, please remember that temperature, humidity and insulation conditions will affect the readings.

Time resistance method

The time-resistance method is quite independent of temperature and usually gives conclusive information without a record of previous tests. Compared with contaminated insulating materials, this method is based on the absorption effect of good insulating materials. During this test, the insulation resistance tester will continuously take readings at a specific time and note the difference. If the insulation is good, the test should show a continuous increase in resistance over a period of time.

Dielectric absorption ratio

Dielectric absorption is the ratio of two time resistance readings. For example, dividing the 60-second reading by the 30-second reading with an insulation resistance tester can make the dielectric absorption rate test easier and is known for providing the best results. For example, the insulation resistance tester can run for 60 seconds; however, it allows you to record readings at 30-second intervals and 60-second intervals.