Students training aid for testing insulation resistance. Demonstration shows how an insulation resistance test could damage a USB socket outlet and how to overcome this. Test voltage is 500V d.c. and the minimum acceptable value according to BS 7671 is 1 megohms for the whole installation with further investigation when the reading falls below 2 megohms.
Note a 3 lead low earth fault loop impedance test will pickup if you have forgotten to reconnect either the line(s) or neutral(s) of the UBS socket outlet.
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