EBME Forums Forums Maintenance Technical Assistance Erroneous high PE resistance values

Back when I was a Biomed doing high current earth bonding tests I always wondered if it was ever posible, in a case where there were only a few strands left making a the connection, that the test could pass milliseconds before the strands burned out? Would ALWAYS the heating of the strands cause high resistance ?

Remember that there is usually a time element to the PE test.

Perhaps the only "belts and braces" method is a 10 Amp test for five seconds, followed by a low current test thirty seconds or so later! Hopefully (and if all is well), the same resistance readings should be achieved. How about that?

Remember where you heard it first, folks!

But using the high current may mask a real problem such as poorly oxidised contacts that are fixed by the application of a high current..... until the connector is disconnected and re-connected causing the high resistance to return! Not exactly safe!

I am now coming to the conclusion that we should stick to a low current test and look for the source of any failure with this low current. Maybe the annual replacement of all IEC mains leads will become a ritual!

Yes, but an expensive (and time consuming) one, perhaps ... suitable only for government hospitals!

OK, let's try the other way around:- the low current test first, followed immediately by 10 Amps for five seconds. If the results are the same, then everyone should be happy.

Followed, of course, by a second low current test, just to be sure!

It looks like good news, then, Bill.

A link that still works.