A look at the Uni-T UT210E

[joeqsmith]

Well they were looking at the 10mA D model, so this may not be too bad. 

I attempted to run the test as described.  I closed off the room but its starting to cool a bit.   I let it collect for a little over a half hour and get a standard deviation of 0.0009398.   P-P was 6.10922mA. 

If you set it down in 2mA mode and watch the meter without touching it, expect it to drift beyond 10mA in about a minute. I haven't done any testing beyond that, but I've seen offsets of a few hundred mA while setting up, just moving the meter around. So I don't expect prolongued measurements to be very useful; zeroing is an essential part of the measurement. If you need to track power consumption ever time, you should use this procedure: zero, clamp on, read value, clamp off, repeat after a couple of minutes.

Mind you, this applies to DC measurements, which are difficult to do with a clamp because of $physics. Any DC clamp will have the same problem. It's much easier to get good AC readings

[joeqsmith]

I left a power supply on during this time to get it warmed up and restarted the same test with roughly 60mA.   This time I am paying closer attention to the LCD on the clamp.  The numbers look better than I would expect.    The highest I saw on the UT210E's LCD was 59mA and the lowest was 56mA.   Looking at the logged data, the P-P was 3.9908mA.  Standard deviation was 0.0005918.   Not sure why it is tighter.  Temperature may be more stable.    Still, less than one count of the meter they were looking at.

I have attached the plots for completeness.  The X-axis is time in seconds.   

[obd.tech]

Well Joe....what can i say.....apart from 'Brilliant'     
That was just what i was trying to find out 

Your scientific approach now makes me understand why you are a 'SUPER Contributor'.....Great Stuff 

4-6mA drift is an excellent result and 100% usable.
Have you any idea if your others (ones not modded) are similar in performance?
Do you think the firmware mod that make it read to 6 or 8000 counts(but no zero  ) might affect it's drift/accuracy?  6 or 8 amps down to 1mA would be ultra useful 
I'm actually looking to get the UT210E with the 1mA resolution, the info about the UT210'D' (with 10mA) was just to make people aware/give them the option.
Thanks again for your Excellent help 

So a clamp for DC= useless?

Hell NO.......i'd be lost without using my one for car current draw. Stable = Brilliant.  Unstable = Useless!!
If you start pulling circuits, you just make more problems. Amp clamp is THE only way to go.

[joeqsmith]

Changing the PROM will not impact the drift.   I suspect you could run 100 of them an they would all drift roughly the same.   I suspect you two main problem will be temperature and placement.   When Maxlor posted 10mA in a minute, I can believe it.   When I ran that test I was careful to try and hold the temperature as tight as possible and not move the clamp.   

Taking a brand new, virgin UT210E and placing it on the bench with no current I measured 14mA of drift after 10 minutes and 19mA after 20 minutes.  This probe is no worse that the one I used for the first test.  What has changed is it is in a room with air conditioning and it is cycling!   

If you are curious what the temperature coefficient is for the UT210E, I took this same unit and put it into a temperature controlled environmental chamber.   I let is settle at 25 deg C and zeroed out the meter.   I then decreased the temperature 10 degrees and let it settle.  The clamp displayed 140mA!  I then increased the temperature 20 degrees, to 35 C.   The clamp displayed -163mA.   303mA/20deg or 15mA/deg C.   

Well Joe....what can i say.....apart from 'Brilliant'     
That was just what i was trying to find out 

Your scientific approach now makes me understand why you are a 'SUPER Contributor'.....Great Stuff 

4-6mA drift is an excellent result and 100% usable.
Have you any idea if your others (ones not modded) are similar in performance?
Do you think the firmware mod that make it read to 6 or 8000 counts(but no zero  ) might affect it's drift/accuracy?  6 or 8 amps down to 1mA would be ultra useful 
I'm actually looking to get the UT210E with the 1mA resolution, the info about the UT210'D' (with 10mA) was just to make people aware/give them the option.
Thanks again for your Excellent help 

So a clamp for DC= useless?

Hell NO.......i'd be lost without using my one for car current draw. Stable = Brilliant.  Unstable = Useless!!
If you start pulling circuits, you just make more problems. Amp clamp is THE only way to go.

[bitseeker]

Excellent testing, Joe. I haven't gone to such a rigorous approach, but anecdotally, when I first bought my 210E, I noticed that it would drift 2-3 mA when measuring small DC currents if I let it sit for several to a dozen seconds. Having seen that, I always zero just before taking a measurement.

[CUDA]

Big thanks to Maxlor for the review, i ordered one and im really happy with it   
Already has seen good use when i rescued a friend who had empty car battery. Jumper cables from my car to his and i could see how much current was flowing to recharge (10-20A).
So convinient to measure current straight from cables. Seems accurate enough even down to tens of mA.

Now all it needs is latching backlight mod....like all multimeters

[TheAmmoniacal]

Does it have any form of inrush current measurement? Like a fast peak detect / min/max?

[Maxlor]

No.

[timofonic]

No.

Is that technically possible in a DMM?

[Maxlor]

Yeah it is, it's actually a pretty common feature among more expensive clamp meters.

[timofonic]

Yeah it is, it's actually a pretty common feature among more expensive clamp meters.

What ones? How do they do it?

Is it possible to hack cheap ones to provide at least such features?

[bitwelder]

If a meter is too slow to catch a fast event, I somehow doubt that it's possible to make an (economically viable and safe) hack.

[DEHiCKA]

Is it possible to hack cheap ones to provide at least such features?

UT210E chipset itself does have support for MIN/MAX.
I've tried to hack MIN/MAX button by connecting pins 26 and 23, witch are used for this function in the other DTM0660L DMMs.
No luck Looks like it's not supported by the firmware as well as RS232 data output (pin 22).
MIN/MAX and RS232 is the only major functions I really miss in this little clamps.

P.S. Attached reference schematic from the datasheet

[Rolo]

Nice read, looking at all the comments one thing looks to be high on the wish list list and that is remote read out.
So I would like to have this imaginary meter :
Clamp type like this UT210, ranges and resulution like this UT210, no display, only current measurement (AC/DC), zero button, auto power off, bluetooth module, no input/output jacks and a nice app on my phone to read the values. Price arround $50.
This should possible, why isn't this on the market ?

 

[Circlotron]

Jumping back a bit in the discussion, I'd like to see what the low current measurement drift is like with the meter running on an external regulated supply rather than it's own batteries, and also if the drift changes much with different but constant supply voltage.

[joeqsmith]

My guess is temperature will dominate the drift.  If long term stability is important, you will need to control that.   

Jumping back a bit in the discussion, I'd like to see what the low current measurement drift is like with the meter running on an external regulated supply rather than it's own batteries, and also if the drift changes much with different but constant supply voltage.

[itsthatidotagain]

Not sure if this is quite on topic, however if you want a cheap multimeter to experiment with, that appears, like the Uni-T UT210E, to be based on the DTM0660, you could try a Victor VC 921 pocket multimeter, but get the one with “True RMS” on the front, as there appears to be an earlier version based on a different chipset.

A full set of teardown pictures are here. https://photos.google.com/share/AF1QipPykJgrz2vMySXTkFdst6YsfoTs0Mzs1vmWZXa-XQ5EGBxVeRmFiqj-jO2c44IFcA?key=T01ITXVCa015U0x5WV9UZUV6dUdiSGdXUTBENF93

As you can see from the pictures, the pinout of the epoxy blob matches the DTM0660 and there is the tell tale 24c02 eerom, and even the two additional buttons needed for calibration, on the back of the PCB.

When I get a spare moment, I’m going to solder a couple of wires on to the thing and see if my hunch is correct. If so, this will be the cheapest 6000 count meter with RS232 (some soldering required) on the market. :¬)

Bear in mind I haven't actually proven that this is a DTM0660 meter, and I wouldn't actually recommend it as a multimeter, since the construction is incredibly cheap, but if you want something to hack, and are only using it for low voltage experiments, it would make a pretty neat $10 logging DMM.

http://www.ebay.com/sch/i.html?_from=R40&_sacat=0&_nkw=Victor+VC921&_sop=15

[Circlotron]

I was using my UT210E on the bench yesterday and after 5 minutes or so it would beep, then a short time later it would shut down. Nothing unusual about that, just saving the battery. The thing is, I would have to turn it off, turn the DC current I was monitoring off, turn the meter on again, put it to DC, zero it, then turn the DC current back on again! It would be so much better if when it beeped I could simply push one of the buttons and make it continue another 5 minutes. Any way to add that facility? Or does it already exist and I haven't seen it?

[3db]

I was using my UT210E on the bench yesterday and after 5 minutes or so it would beep, then a short time later it would shut down. Nothing unusual about that, just saving the battery. The thing is, I would have to turn it off, turn the DC current I was monitoring off, turn the meter on again, put it to DC, zero it, then turn the DC current back on again! It would be so much better if when it beeped I could simply push one of the buttons and make it continue another 5 minutes. Any way to add that facility? Or does it already exist and I haven't seen it?

I don't have mine here at the moment but from memory you hold down select then switch the meter on.
I'm sure that kills the auto poweroff.
3DB 

[thisguy]

Yes, 1 mA resolution DC and AC. But you have to keep in mind that simply moving the meter around in free air can on DC introduce +/- 10 mA easily, from earth's and other stray magnetic fields.
Still a great low current DC clamp meter for the price.

The DC reading on my new UT210E varies as much as +-120mA just from moving it around in free air. Is this typical, or does the meter have a problem?

[bitseeker]

Do not move the meter when taking a measurement with the clamp, especially for small DC currents. Zero the meter and read the measurement as soon as possible without changing its position and orientation. When you move the meter, you change the way any magnetic fields in the environment act on the clamp, and hence affect the measured value.

For AC current and large DC currents, the environment isn't a big influence relative to what's being measured. However, when using this clamp to measure very small DC currents, technique is important.

Edit: Tidied up wording.

[thisguy]

Do not move the meter when taking a measurement with the clamp, especially for small DC currents. Zero the meter and read the measurement as soon as possible without changing its position and orientation. When you move the meter, you change the way any magnetic fields in the environment act on the clamp, and hence affect the measured value.

Thank you. I understand. But is +/-120mA typical for the meter?  Rotating my meter by 180deg can change the reading by 240mA. Thats 1 1/3 mA change in reading per degree of rotation. If that magnitude is typical and expected due to the earths magnetic field, then I've learned something and I'll keep in mind that a very steady hand is required to get 10mA accuracy, and that it's probably not possible to get better than 5mA accuracy by hand. On the other hand, if it indicates that the meter has a problem, I'll return it for a better copy.

[bitseeker]

That's a pretty high variation, but consider that the Earth isn't the only source of magnetic fields. You may be picking up something from other electronic devices, power lines, large metal objects (desk/workbench?), etc.

See if you get the same behavior outdoors. It's possible the issue is with the meter, but it'd be the first I've heard of it for the UT210E.

[thisguy]

That's a pretty high variation, but consider that the Earth isn't the only source of magnetic fields. You may be picking up something from other electronic devices, power lines, large metal objects (desk/workbench?), etc.

See if you get the same behavior outdoors. It's possible the issue is with the meter, but it'd be the first I've heard of it for the UT210E.

Thanks for the suggestion.
There are no major transmission lines visible from my location, and local power is distributed via underground wires. I took the meter outside and tested in two different locations separated by 100 feet or so.  Before being zeroed, the meter reads in the 320-430mA range.  After zeroing the meter, I tested variability based on orientation.  Slightly rotated and tilted up and it read 130mA . Tilted it down, -75mA.  The variation was similar when tested in the other location.  (Biggest change tends to happen when tilting up vs down.)  So today, outside, the variation is around 210mA. I saw earlier in the thread that the meter could become magnetized and require degaussing.  I understand this could cause an offset in the reading, but it's not clear to me if it could also cause the variation based on orientation that I'm seeing. Also, I'm not sure which of my power tools or appliances would leak enough EMF to use as a degausser.
So my question is is this typical behavior for the meter, or should I exchange it for another? What do others see?
Thanks

[bitseeker]

Thanks for doing the additional tests. It sounds unusual to me, but let's see if anyone else has more info.