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Clamp on ammeter.

PostPosted:Tue Apr 16, 2019 3:36 pm
by Charles Hunt
I understand that one should only put the clamp around one of the conductors, but am perplexed that I get significantly different readings depending on whether I clamp the +ve or -ve lead.

Surely current around a circuit is constant.

Am I missing something?

Re: Clamp on ammeter.

PostPosted:Tue Apr 16, 2019 3:43 pm
by Paul_Sengupta
Maybe you have a leak.

Is this AC or DC? If DC, is the clamp meter actually a DC capable one?

Re: Clamp on ammeter.

PostPosted:Tue Apr 16, 2019 7:01 pm
by Charles Hunt
DC. And yes.

Re: Clamp on ammeter.

PostPosted:Tue Apr 16, 2019 7:05 pm
by Paul_Sengupta
Are you zeroing it in-situ before you turn the power on?

Re: Clamp on ammeter.

PostPosted:Tue Apr 16, 2019 7:40 pm
by Charles Hunt
Not aware of a zeroing function. Haven’t got it with me at the moment.

Not aware of a knurled knob on the side, is there a standard method of zeroing these modern digital things?

Re: Clamp on ammeter.

PostPosted:Tue Apr 16, 2019 7:46 pm
by Charles Hunt
Clas Ohlson UT203

Re: Clamp on ammeter.

PostPosted:Tue Apr 16, 2019 8:48 pm
by Paul_Sengupta
Charles Hunt wrote:Not aware of a zeroing function. Haven’t got it with me at the moment.


"Press [Rel Δ] to clear the display"

Page 13.

Re: Clamp on ammeter.

PostPosted:Tue Apr 16, 2019 10:16 pm
by Charles Hunt
Many thanks, will give it a go.

Re: Clamp on ammeter.

PostPosted:Thu Apr 18, 2019 7:30 am
by Nomad63
Also, when you zero it make sure you do so with the meter as close to the position it will be when you actually clamp around the wire.
In my experience the zero calibration varies as you move them around close to other wiring, which could explain the difference in the +ve _ve wires if you are not calibrating zero when close to the measuring position.

Re: Clamp on ammeter.

PostPosted:Thu Apr 18, 2019 10:09 am
by Charles Hunt
Gave it a quick go yesterday and trying to get a steady zero and then get it over a wire half way down the fuselage gave meaningless results.

Current can’t flow if there’s infinite resistance so maybe a simple resistance check will show if there really is a drain problem. New master switch fitted.

Re: Clamp on ammeter.

PostPosted:Thu Apr 18, 2019 7:17 pm
by Lerk
Current around a series circuit is constant as you say, which may mean that what you are measuring on the -ve is one leg of a parallel circuit. Ie some of the -ve is going back through the body.