Over here in NZ, we have a Standard, called
AS/NZS 3760, that tells us what is required for these tests, and also how often they should be done.
not sure if it is there are not.
But, long story longer, when testing appliances, it depends upon what Class of
Equipment it is:
Class I: Earthed, with metal casing.
Class II: Double Insulated, with non-conductive casing, but may have exposed metallic parts, which are isolated from Earth.
Class III:Protected by RCD(GFCI).
Now, for a Class I appliance, a Resistance test with an Ohmmeter, between the Earth pin of the Plug and the Metal case of the said appliance, this must not be any higher than
0.5Ohm, for safety reasons.
Also, an Insulation Resistance Test, using a Megger, should be applied, by bridging out the Phase and Neutral pins of the plug and connecting the other lead to the Earth pin of the plug, anything less than about 100Megohms, should worry you.
Finally, with Class II appliances, there is really only the Insulation Resistance test, that can be done on these appliances,but the probe that would normally be fitted to the Earth pin is connected to any exposed metal,(like Drill chucks, etc), a very high reading is expected from this test,(>200MOhms).
A Class III appliance, is tested in the same way as the Class I appliance, except the RCD is disconnected first and tested seperately,with a dedicated RCD(GFCI)tester.
As a side note, when doing any appliance testing, it is good practice to check the
appliance for physical faults, too, especially with flexible cords, run the whole length of the flex, through your closed hand, any irregularities, felt, should be checked.
Hope this helps.
[This message has been edited by Trumpy (edited 02-10-2003).]