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Old 4th Aug 2020, 11:54 am   #1
Join Date: Dec 2008
Location: Wincanton, Somerset, UK.
Posts: 1,146
Default RCD nuisance tripping and other problems?

I friend has had intermittent tripping of his consumer-unit master RCD, so in an attempt to trace the problem, he bought one of these clamps.

They are available under various brand-names, but clearly come from the same source in the far east. I bought a ProPower-badged example from CPC, which seems to be a good deal.

It measured 30mA @50Hz pretty much spot-on, and is certainly much better than the 5% spec. I then checked its frequency response, which seems to be flat to around 2kHz, with a gentle roll-off above that.

So it could also be used for checking e.g. loudspeaker impedance while still in circuit, using say 400Hz or 1kHz tone.
The only thing to watch is that it's susceptible to stray magnetic fields, so will read several mA if too close to the Weller transformer!

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