| 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 an 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.
|
| Q. |
What is trending? |
| 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.
|
|
|
