I got hold of a second hand one of these:
A HEME 100 clamp meter.
I can't find specs for it online, only a HEME 1010.
I've tried reading a few currents with it (using a brand new battery in it), and it seems to underread a fair bit on DC (0.56A instead of 0.62A) and AC (7.5A instead of 8.5A). It's also susceptible to wires near it - for example if you put the live inside the clamp but the neutral is an inch or so from the outside of the clamp, it reads a bit of that too and gives a higher reading. Are these things supposed to be accurate? Can I adjust it?
How are you measuring the reference currents of 0.62A and 8.5A?
Using the specification of the HEME 1010
You are on the 400Amp range with a resolution of 0.1A
The accuracy is +/-5 digits (+/- 0.5 Amps) plus 1.3% of reading (0.1A)
so the reading is 6A +/-0.6A
If you are using a multimeter as the comparison it may be equally
inaccurate, especially if the internal battery is failing. Often a
failing battery in a multimeter gives high readings.
The 0.62A was with a decent multimeter connected in the circuit.
The 8.5A was measured both with one of those energy efficiency meters on my house's meter tail, and by knowing what devices were running.
It's a HEME 100, not 1010.
There is no range selectable, it's automatic?
That's a hell of an error margin, but still way less than what I'm getting.
Also, taking the same reading in the same circuit repeatedly is giving widely varying readings, between 50% too low and 10% too low. I've thrown it in the bin.
I know the multimeter is accurate, I've tested it on all sorts of things.
The only way you will know that your multimeter is accurate is by having
it calibrated against a known standard, ideally specified to 10x better
than your meter.
At 0.65A a high end Fluke multimeter @ £200+ will give 0.65A +/- 0.01A
on a typical £50 multimeter £50 it will give 0.65A +/-0.09A
Without a specification for what you have purchased, you may have meter
capable of measuring fairly accurately currents in the range 100A to
1000A but not capable of 0 to 10A measurements with any degree of accuracy
Typically you may be trying to measure and compare a 0.65A current with
measuring equipment with a total uncertainty of measurement of around 0.6A
> The 8.5A was measured both with one of those energy efficiency meters
> on my house's meter tail, and by knowing what devices were running.
So your comparison standard is something British Gas used to give away
for free, possible so inaccurate that it hasn't got a published
specification for its current measuring capability.
If you are measuring volts then ac is best on a calibrated scope of course,
but I've seen some very strange results from clamp meters in the past, and
after all there are a lot of variables going on all at once.
This newsgroup posting comes to you directly from...
I didn't know you could measure volts with the clamp part of a clamp meter.
If it is of the newer (as in less than 25 years old) hall effect sensor
devices then it will be more susceptable to stray magnetic fields. There
should be a calibrate/zero button on it somewhere which you should use
just before you clamp on to cancel all these effects out before measurement.
If you clamp both active and neutral they will cancel out and you
will get no reading.
I have a Clamp Leaker 140.
Any idea how old?
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