DC clamp meter. Uni-T UT216C

[rsgaz]

Hi all,

There's been a few discussions on here over the years about how they work, how accurate, etc. Here's my findings of my new multimeter I bought to play with!

My tired old Fluke can't do true RMS, nor frequency, capacitance, etc, so I bought a UT216C...



The case is awful, that other thing is a thermocouple.

Only just got it today, so this is not a review, but I was just very impressed with the very first thing I wanted to try out, DC current, so I thought I'd share my findings. This is readings of an in car fridge, hooked up to a 13.8v power supply...



I'd say that's near as dang it!

I thought it would be picky about the position of the wire going through, or picky about keeping the wire perpendicular, but it isn't. I guess I still don't understand how the DC ones work!!

 

[EFLImpudence]

I have a Uni-T UT210E. I have only used it in for vehicles.

The position of the wire doesn't seem to matter too much but you have to zero the reading every time you use it on d.c. and then keep the meter in the same orientation. If you rotate it the reading changes because apparently the world is d.c.

It does seeem to be quite accurate and it has quite good reviews.

 

[plugwash]

IIRC/AIUI

A traditional clamp meter is a current transformer, electric current causes a magnetic field in the core which induces an electric current. The primary has a single turn while the secondary has multiple terms, so the transformer steps down the current and steps up the voltage.

Traditional clamp meters don't work on DC because while DC electric currents can create magnetic fields, static magnetic fields cannot induce current.

DC clamp meters insert a hall-effect sensor into the core, in theory this could be used to take the measurement directly but in practice non-linearity makes that a bad solution. So a better solution is to inject a current in the "secondary" to zero-out the magnetic field in the core. The current needed to zero-out the magnetism can then be measured.

I suspect the orientation issue is a sensitivity to external magnetic fields.

 

[EFLImpudence]

I suspect the orientation issue is a sensitivity to external magnetic fields.

Yes, that's correct.

I tried to record the different values but there are too many variations. It depends which way up the meter is.
E.g. laid horizontal face up or face down and stood on one edge or the other and rotated in different planes.

Once zeroed the reading ranges from 0.000 to 0.050DCA.

 

[EFLImpudence]

I should have said - the lowest reading obtained by rotating before zeroing was 0.189A

 

[plugwash]

So basically it's useful for high current DC systems (like cars) but even with zeroing it's nowhere near accurate enough for microelectronics work.

Good to know.

 

[EFLImpudence]

You're likely correct.

Are there any better (less susceptable) DC clamp meters available?

 

[aptsys]

A traditional clamp meter is a current transformer, electric current causes a magnetic field in the core which induces an electric current. The primary has a single turn while the secondary has multiple terms, so the transformer steps down the current and steps up the voltage.

Sort of. It 'may' step up the voltage, but that's really the job of your transimpedance stage on the output of the transformer, all it's really doing it doing whatever it can to keep a proportional current flowing through the secondary.

 

[rsgaz]

it's useful for high current DC systems (like cars) but even with zeroing it's nowhere near accurate enough for microelectronics

I did some more tests, and yes, you're right!

Still close enough at half an amp, the reading was stable...

Red 12v 382 LED, (tinfoil so the photo is legible!)

With a small 501 LED, it was fluctuating between 0.02 and 0.05, despite the Fluke staying at 0.03. I was not moving, the meter hadn't moved. The only other possible nearby influences nearby was the PSU, a switched off TV and the phone/camera of course.



It has it's uses, for sure, I'm pleased with it. But accuracy at below about a quarter of an amp is not to be trusted.


@EFLImpudence

I'm not experiencing anywhere near the fluctuations that you have reported relating to orientation. Still agree on the need to zero it every single use though.

 

[EFLImpudence]

I'm not experiencing anywhere near the fluctuations that you have reported relating to orientation. Still agree on the need to zero it every single use though.

No ?

Perhaps it's extra magnetic here or it was my couch.

No, it's still the same holding it while stood up and turning round.

 

[rsgaz]

No ?

I just tried again. During the moving it around/rotating/etc, I can get it to read as high a ±0.05. As soon as I stop (in any orientation) it settles down to ±0.01 usually. Only occasionally 0.00.

I guess in use it's no problem really, I'll just zero it just before putting the wire in the loop.

 

[EFLImpudence]

I just tried again. During the moving it around/rotating/etc, I can get it to read as high a ±0.05.

Do you only have two decimal places on yours? Mine has three.
Of course ± 0.05 is a 100mA difference.

As soon as I stop (in any orientation) it settles down to ±0.01 usually. Only occasionally 0.00.

Mine doesn't do that, but again that could be anything between + 19 or -19mA depending on how it works.

I guess in use it's no problem really, I'll just zero it just before putting the wire in the loop.

No, I have found it accurate if you don't move it when switching things on and off in the vehicles - or waiting for the computer to turn off things.

 

[rsgaz]

Do you only have two decimal places on yours?

Yes, for AC or DC current, it's resolution is only 10mA.

 

[DetlefSchmitz]

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

 

[mikeyd]

The UT210E has a low range of 0-2A (and a max of 100A), whereas the UT216C has a low range of 0-60A (and a max of 600A) so they are not really comparable at low mA levels.

I have a 210E and think it's excellent for the price. I used it the other day on an underperforming solar install to quickly identify half the panels are open circuit (They are wired back to the invertor in 2 parallel strings). As it's about 300V DC and I'm not used to working on such things, I personally would not have wanted to start disconnecting cables to test it live with a traditional meter.