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Minimum values of insulation resistance

Wombat
What is the science behind the 1 MOhm minimum insulation resistance? What is the basis for this particular value?
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    AJJewsbury:




    Not quite. If you get 1 MΩ for a whole board IR test, you know that all circuits have passed. However, if it is less, then you need to test each circuit separately.



    OK, it's late and I'm usually slow on the uptake, but why? If a whole board IR comes in at less than 1MΩ - then isn't it just a simple fail? (working out which is the culprit is fault-finding rather than testing).


    Ok, think of it the other way around. Instead of thinking about splitting a group of circuits, ask yourself why it is that you can group them in the first place. In the case of an initial verification, each circuit is tested individually before connecting it to the CU. That avoids a big bang test. However, that is not an issue for periodic inspection and testing so you can save time and effort by testing the circuits as a group.


    So here's a question for those of you who do routine periodics day in, day out. How often is there a fail on IR testing in the absence of a reported problem. I suspect very rarely indeed.

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  • 0

    AJJewsbury:




    Not quite. If you get 1 MΩ for a whole board IR test, you know that all circuits have passed. However, if it is less, then you need to test each circuit separately.



    OK, it's late and I'm usually slow on the uptake, but why? If a whole board IR comes in at less than 1MΩ - then isn't it just a simple fail? (working out which is the culprit is fault-finding rather than testing).


    Ok, think of it the other way around. Instead of thinking about splitting a group of circuits, ask yourself why it is that you can group them in the first place. In the case of an initial verification, each circuit is tested individually before connecting it to the CU. That avoids a big bang test. However, that is not an issue for periodic inspection and testing so you can save time and effort by testing the circuits as a group.


    So here's a question for those of you who do routine periodics day in, day out. How often is there a fail on IR testing in the absence of a reported problem. I suspect very rarely indeed.

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