| Q. |
What is an Insulation Resistance Test? |
| A. |
An Insulation Resistance test measures the total resistance of a product's insulation system. The test is usually performed as a quick check after a product is manufactured, installed or repaired. It is also a useful test to perform when doing preventative maintenance on a product over time. Changes in the insulation measurement can help to predict if a product such as a motor, cable or component is due to fail. |
| Q. |
What is the difference between a Megohmmeter and Insulation Resistance Tester? |
| A. |
They are essentially the same. A Megohmmeter refers to an instrument whose meter is usually scaled to read in MΩ (millions of Ω's). An Insulation Resistance tester refers to an instrument that measures the resistance of a product's insulation system. |
| Q. |
What is the difference between a Hipot test and an Insulation Resistance test? |
| A. |
The Insulation Resistance test is a qualitative test that gives an indication of the relative quality of a product's insulation system. This is an ideal test for studying, measuring and recording long term stability of insulating materials over time. The Hipot test is commonly specified as a production line test for electrical products. The Hipot applies an excessive voltage between the current carrying and non-current carrying parts of the DUT to stress the insulation system and verify its integrity. |
| Q. |
What is considered to be an acceptable Insulation Resistance reading? |
| A. |
This can vary from product to product and is often dependant on several factors including humidity, temperature and dust. Contact your local safety agency office or our Technical Services department for more information. |
| Q. |
What is the Polarization Index? |
| A. |
Polarization is the ability for a material's dipoles (equal and opposite charges separated by some distance) to line up in the presence of an electric field. As the dipoles align themselves absorption current is created that decreases over time. Initially the absorption current is high, but as fewer and fewer dipoles are left to align themselves with the applied field the current drops. Thus an IR measurement taken after 1 second would yield a lower resistance than an IR measurement taken at say, 60 seconds. In fact, the most common test times are a 10 minute test divided by a 1 minute test. The resulting ratio of the test measurements is known as the Polarization Index.
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| A. |
Trending is a term used to describe the process of taking repeated test measurements over time. In the case of Insulation Resistance testing, trending the test results can provide useful information about a product's integrity and can yield clues as to when its insulation should be repaired or replaced. |
