On 2018-01-09 21:45, newshound wrote:
On 09/01/2018 16:48, Graham Nye wrote:
On 2018-01-05 15:43, newshound wrote:
On 05/01/2018 08:52, Roger Hayter wrote:
newshound wrote:


Can you test both instruments on a one megohm high voltage resistor?

That test was with the element removed. I agree that 5 meg is defective,
but wouldn't necessarily trip an RCD. Didn't have any suitable resistors
to hand when checking...

You've already told us you've got one. Your DVM should have a constant
input resistance (usually 10 MOhms, but check the manual). So, while
you're reading the 320 V output of the Megger on your DVM also check the
Megger to see what resistance it sees looking in to the DVM.


Didn't think of that! I have a collection of DVMs but I think the
manuals are long gone. Could of course do some cross calibration.

If you have multiple DMMs you can use one to check the input resistance
of another at the low voltage used by a DMM. You can then use the
checked one with the Megger.



--
Graham Nye
news(a)thenyes.org.uk