DC clamp meter. Uni-T UT216C

[JohnW2]

You could put ten turns through the jaws to measure lower currents (and divide reading by ten).

Does that necessarily work 'as expected' with hall-effect devices? I really don't know.

Kind Regards, John

 

[EFLImpudence]

I don't know either but surely it must otherwise it would only work on single cores.

I.e. not multiple circuits in bunches - or is that different?

 

[rsgaz]

The figures seem to correlate nicely enough.

This time, P21W lamp...

 

[JohnW2]

I don't know either but surely it must otherwise it would only work on single cores.

I don't know enough about the theory and behaviour of hall-effect devices, but rsgaz's experiment seems to indicate that is does work 'as wexpected'.

I.e. not multiple circuits in bunches - or is that different?

It's conceptually very similar but, as above, I would not know (on the b asis of my limited understanding of the theory) whether either would work 'as expected'.

Kind Regards, John

 

[DetlefSchmitz]

Does that necessarily work 'as expected' with hall-effect devices? I really don't know.

I have designed and currently sell test equipment which uses exactly that principle (with a Hall-effect device). You cannee change the laws of physics...

 

[JohnW2]

I have designed and currently sell test equipment which uses exactly that principle (with a Hall-effect device). You cannee change the laws of physics...

Fair enough. As I said, I just didn't know enough about the theory behind, or behaviour of, hall-effect devices to be sure.

Kind Regards, John

 

[rsgaz]

For the sake of completeness

The point of Detlef's 10 turn idea was, of course, so that I can use the meter for milliamp readings. But, seeing as my Fluke only has a 10mA resolution, I just stuck a 21W lamp on there for the sake of the photo, thinking I had no way of comparing lower currents.

But, I just remembered, I have a really cheap nasty meter too, which does do mA and even claims it can read microamps!

I put a 100Ω resistor on the 13.8v PSU, the result being, of course, black smoke!!!

So, I put a 220Ω resistor on there (cheap meter is in 200mA range)...

Again, seems to work well enough.

But, when I swapped it for a 680Ω resistor, with the cheapo meter reading 21.5mA, that annoying fluctuating returned that I had mentioned before. Hopping around from 0.19 to 0.24 on the Uni-T display (times by 10 already, of course).

So I think it's a very good tool overall, but it really seems to dislike DC currents of around a quarter or less amps. It just can't seem to deal with surrounding influences. It never fluctuates for higher readings.

 

[JohnW2]

... But, when I swapped it for a 680Ω resistor, with the cheapo meter reading 21.5mA, that annoying fluctuating returned that I had mentioned before. Hopping around from 0.19 to 0.24 on the Uni-T display (times by 10 already, of course).

Are you quoting those figures correctly? 19-24mA would be close enough to 21.5mA for most purposes, but you appear to be talking about 1.9-2.4mA - which certainly isn't!

Kind Regards, John

 

[rsgaz]

Are you quoting those figures correctly?

Yes. The bit in brackets was supposed to reduce confusion, but I think I may have caused some!

I meant the Uni-T has, unbeknown to it, already multiplied the reading by 10. So it was fluctuating between 190 and 240mA. The reading would just not stop moving though. Every second it changed, the display was going...

0.19 → 0.22 → 0.20 → 0.24 → 0.19 → 0.23 → 0.21 → 0.24 → 0.19 → etc → etc (or something along those lines anyway).

 

[JohnW2]

Yes. The bit in brackets was supposed to reduce confusion, but I think I may have caused some! ... I meant the Uni-T has, unbeknown to it, already multiplied the reading by 10. So it was fluctuating between 190 and 240mA. The reading would just not stop moving though. Every second it changed, the display was going... 0.19 → 0.22 → 0.20 → 0.24 → 0.19 → 0.23 → 0.21 → 0.24 → 0.19 → etc → etc (or something along those lines anyway).

Ah, I think I now understand, and it doesn't look too bad at all.

When I wrote before, I was thinking that the Unit-T results you were reporting were in mA, and that the bit in brackets meant that we had to multiply them by 10. However, as I said, if one did that, the answers would still be around 10 times smaller than they should be.

It is now apparent that the readings were in A, not mA. Since you had 10 turns, one needs to divide your readings by 10, so the 190mA-240mA (0.19A - 0.24A) figures become 19mA-24mA - which I would think is, for many/most purposes, close enough to the 'true' 21.5mA to render it a fairly useful machine. Indeed, given what has been said about the position/movement/orientation-sensitivity of the device, those figures seem remarkably good.

Kind Regards, John

 

[blup]

Agree it fluctuates on lower readings, ok on higher ones.

(Using the clamp feature, that is).

Blup