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UT210E Problem measuring AMPS!!! :(

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2N3055:

--- Quote from: joeqsmith on May 12, 2020, 07:44:44 pm ---
--- Quote from: 2N3055 on May 12, 2020, 07:22:06 pm ---
--- Quote from: NoisyBoy on May 12, 2020, 04:57:28 pm ---This is a clamp meter with a 2.5% +/-5 digits spec, so you will only achieve +/- 0.1A accuracy at low amperage (like below 4A).  So temper your expectation on what this meter can really deliver in terms of accuracy.  Due to its design, it is hard to achieve the 0.1A accuracy in clamp meters throughout its measurement range even for expensive meters, let alone a $10 Uni-T.

--- End quote ---
It has 2A range.. 2.5% +/-5  is +/-5mA+/-5d max error..

--- End quote ---

I'm going to say It has 2A range.. 2.5% +/-5  is  +/-50mA +/-5d or +/-55mA.    Maybe we can vote on it and see who's right.  :-DD

--- End quote ---
You are, had a brain fart...

AVGresponding:
Don't be too quick to write off cheap clamp meters, unless you've checked the thing first.

I have a cheap Mastech 2108A, icr what it cost, but was certainly less than 30USD.

The low dc range is 40A, with 10mA resolution.

Obviously I was curious about the accuracy, so I gave it some on the job testing.
I was helping out a fellow sparky who was commissioning a small fire alarm panel; he'd found the current draw was so small that putting his DMM in series on mA setting (Fluke 77 iirc) the panel just wouldn't power up.
The reason you need to do this is for fire regs, you have to measure the quiescent current and the full alarm current as part of the battery capacity formula.
So I used the Mastech, and we were looking at around 30mA quiescent, and 50mA with all the sounders running.
Since that's effectively in the noise as far as this meter goes, I was rather sceptical, and went for a rummage around in my van, and dug out a precision shunt I'd made.
Using this we measured the currents again... and found them the same, though with the shunt we got an order of magnitude better precision.
Nevertheless I was pretty surprised, and even impressed, with the performance of the cheap clamp meter.

NoisyBoy:
Good point, I have seen similar scenarios before.

However, I have also observed cheap meters often are nonlinear in reading.  The error may be low at some point, but huge at others, and likely you can even find a point where it is dead-on if you run it through a calibrator, but I would be careful to rate any overall accuracy from limited data points. 

Meters with good linear results are those with multiple cal points across each function and on each range selected, unfortunately, most low cost meters do not offer it. 

So, while at some amperage range, the Uni-T may offer <.1A accuracy.  My point is it is very unlikely that it will deliver this accuracy across a wide current range.

AVGresponding:
That's a fair point, and tbh I've not checked it at the other end of the range.

The aforementioned shunt will measure up to 70A or so before it becomes too hot to handle, so now I just need to fathom a 39A or so load to check them against each other...

cdev:
My UT2010E meets the specs - it can measure a low current to 1 ma accuracy, which for the price was a great deal. Also the non contact meter is very useful. And it has a decent voltmeter, ohmmeter, so I think it was a great purchase. I wish it could connect to a USB port, but you cant have everything. I paid around $30.00 for it. Totally happy with it.

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