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Insulation Resistance Measurements

Former Community Member
Former Community Member
Hello,


We have a Insulation Resistance measurement unit from Hioki - ST5520.

We are using this to measure multiple devices controlled through a relay matrix as shown in the figure. The positive and negative terminals of the ST5520 is multiplexed through the relay matrix to the 64 pins of the connector. There are 7 pcb's each containing 20 relays.

The individual board testing from ST5520 to the connector is giving a open condition result with a high value of insulation resistance of 9.90Gohm @1000V, when there is no load at the connector output, it is left open.

But the when the whole system is wired and tested with the 7 pcb's(all 32 channels), the value fluctuates and starts with a value from 100Mohm and eventually reaches open condition value.

Is there a problem with this process of multiple channel testing? or this is the expected behaviour? the open condition value(9.90Gohm@1000V) is maintained once it reaches this value and further tests result in this same value. 

Once the system is left OFF for a period of a day, then the testing is resumed again, the same behaviour of starting from 100Mohm to open condition value repeats. Is this to be expected or i am understanding/ doing something wrong?

Any help with this is much appreciated. Thanks in advance.
0d3eb1e11f9f4ba9176cae1b22dc1e68-huge-insulation-measurement.png
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  • Former Community Member
    0 Former Community Member
    Sparkingchip:

    Presumably you are doing a timed test, unlike installation electricians who press the button and hold it down for a random period.


    So surely if it is a timed test being carried out in accordance with the required standards, if it passes at the end of the timed period everything is hunky dory?

    https://www.hioki.com/en/products/detail/?product_key=5780


    Andy Betteridge


     


    Thanks for the reply. 


    Yes we are doing a timed test, which is though the software commands, not the buttons on the ST5520. 

    The problem with the result now is that it is taking lot of time to reach the open condition and the setup is open ended with no load. Ultimately this has to be tested with the load, we cannot wait everytime for the system to reach open condition and then connect the load.


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  • Former Community Member
    0 Former Community Member
    Sparkingchip:

    Presumably you are doing a timed test, unlike installation electricians who press the button and hold it down for a random period.


    So surely if it is a timed test being carried out in accordance with the required standards, if it passes at the end of the timed period everything is hunky dory?

    https://www.hioki.com/en/products/detail/?product_key=5780


    Andy Betteridge


     


    Thanks for the reply. 


    Yes we are doing a timed test, which is though the software commands, not the buttons on the ST5520. 

    The problem with the result now is that it is taking lot of time to reach the open condition and the setup is open ended with no load. Ultimately this has to be tested with the load, we cannot wait everytime for the system to reach open condition and then connect the load.


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