Question about clamp meters

Ray Pooley · Dec 18, 2019

Well, I say that because I don't think there is a problem other than perhaps my meter reading.

Then again, it might not be a problem at all.

So I had an oil heater that was tripping the RCD. Element was leaking so replaced it.

Also did a complete check of all switches, terminal blocks and cables looking for grounding and all is fine.

Put it all back together, switched it on max and checked the draw on the line with the clamp meter
and it is what I would expect a spot on 10 amps.

So I then clamp the earth cable and it reads 46mA. The RCD is rated 30 mA but it doesn't trip.

Is my meter telling lies or is the clamp picking up the flux from the neighbouring line even though
the line is outside the clamp?

Any thoughts?

Thanks

Ray Pooley

Marvo · Dec 18, 2019

From the details on the website you linked to;

200mV/2V/20V/200V (±1.0%), 600V (±0.7%). AC voltage: 2V/20V/200V (±1.2%), 600V (±0.8%). AC current: 2A/20A (±3.0%), 200A (±2.5%), 600A (±1.5%). Resistance: 200Ω/2kΩ/20kΩ/200kΩ/2MΩ (±1.2%), 20MΩ (±2.0%). Requires 3 x AAA batteries.

It's simply not designed to measure current less than 2 Amps with any accuracy. Yes, it will give a reading but the further away you get from the 2 Amp minimum the more inaccurate the reading will be and any reading less than a few hundred miliAmps should just be ignored completely because it's so far outside the design range of the tester. As already mentioned you need an earth leakage clamp meter to give you any meaningful accuracy in the mA range.