Hi
If you want to kill yourself carry on using your HP 410C to measure AC line voltages. This meter has the AC common connection connected to the case work, should you find an AC outlet that is miss wired the meter case will be at AC supply voltage.
The GFI trips are warning you of this, don’t be stupid.
HP say that this meter MUST NOT be used to measure AC supply voltages.
Engage brain and stay alive.
G Edmonds
Yes I agree this is
bad choice of meter to measure line voltages, its' intended for audio or RF use.
I think we all have the same opinion as the members of the HPAgilentKeysight group and Antique Radio forum, the OP also posted this on, don't use it for AC line voltage measurements.
But the 410B & 410C manuals only give cautions, if the ground clip is connected to an ungrounded line connection a short circuit will result, also all the metalwork (probe body, chassis) would be
live, even worse if the ground wire failed as a result of the short.
They state to use the probe tip only,
but it would be far better to use a modern DMM with appropriate ratings, than something 50+ years old with possibly degraded/perished insulation in the AC probe leads and metal probe body.
David