UT210E out of whack

[mos6502]

I have a UT210E clamp meter that is always off when measuring DC current.

The meter is about a year old and has been very rarely used. Recently, I noticed that it showed an offset of around 4A, which would not allow it to zero in the 2A range. So I opened it up and aligned it using the three pots. I did an alignment before, shortly after I received the meter, and it worked fine then. I even built a degausser to demagnetize the clamp.

A 1A current is measured at around .65 amps, on all ranges. Similarly, a 100mA current is shown at around 65mA. It is very sensitive to the placement of the wire inside the clamp. And no matter how I adjust the pots, the absolute value remains the same. Also, the reading fluctuates pretty wildly when moving the meter around, like +/- 200mA, but I think it did that to some extent when new. It does zero out, but you have to hit the zero button a couple of times to get an actual zero reading. Again, I believe it did that when it was new. Voltage measurement is fine (within 4mV of my Fluke 87).

Any ideas? Or should I just toss it in the garbage?

[fzabkar]

Photos might help.

[mos6502]

Photos of what?

[Armadillo]

Here is the link if you want to see some;

https://www.eevblog.com/forum/testgear/a-look-at-the-uni-t-ut210e/msg560006/#msg560006


Upgrade;

[jfiresto]

If you end up needing another sensitive DC clamp ammeter with plus or minus 1% + 10 x 0.1mA accuracy, the Benning CM 11 looks like a good one. it is, however, about five times as expensive, but still less than half the cost of the durable-looking alternatives I could find. I have had one for a few months and so far it has been great.

[Armadillo]

I like that proximity live detection feature in this UT210E. Robust and Sturdy Construction.
Feels and work great and Cheap.

[fzabkar]

ISTM that there may be a problem in the vicinity of the op-amp. I would return the trimmers to their original positions (or to their centre positions) and measure the op-amp inputs and outputs.

BTW, @Maxlor's review states that the meter should not be moved after zeroing, presumably because it will be influenced by changes in the Earth's magnetic field.

[mos6502]

If you end up needing another sensitive DC clamp ammeter with plus or minus 1% + 10 x 0.1mA accuracy, the Benning CM 11 looks like a good one. it is, however, about five times as expensive, but still less than half the cost of the durable-looking alternatives I could find. I have had one for a few months and so far it has been great.

Looks good, but I already have two other "good" clamp adapters that I can use with my multimeters and scopes, one of them goes down to 1mA. After my last Uni-T abortion I vowed to never buy any of these crap meters again, but sadly I got suckered into buying the UT210E because it looked "nice and compact and it might come in handy". Unfortunately, the construction is garbage (one core glued in cockeyed, giant gaps between the cores) and like other Uni-Ts, in the back of your mind you're always wondering whether it's still good or whether it just crapped out and is only showing garbage. While googling for info about what might be broken I found a bunch of posts by other people who had defecive UT210Es; nothing similar to my symptoms, though.

[joeqsmith]

I have a UT210E clamp meter that is always off when measuring DC current.

The meter is about a year old and has been very rarely used. Recently, I noticed that it showed an offset of around 4A, which would not allow it to zero in the 2A range. So I opened it up and aligned it using the three pots. I did an alignment before, shortly after I received the meter, and it worked fine then. I even built a degausser to demagnetize the clamp.

A 1A current is measured at around .65 amps, on all ranges. Similarly, a 100mA current is shown at around 65mA. It is very sensitive to the placement of the wire inside the clamp. And no matter how I adjust the pots, the absolute value remains the same. Also, the reading fluctuates pretty wildly when moving the meter around, like +/- 200mA, but I think it did that to some extent when new. It does zero out, but you have to hit the zero button a couple of times to get an actual zero reading. Again, I believe it did that when it was new. Voltage measurement is fine (within 4mV of my Fluke 87).

Any ideas? Or should I just toss it in the garbage?

One of mine that is also about a year old became intermittent a month or so ago.  This meter was not modified in any way.  It gets a fair bit of use but I only use the clamp function.   In my case, it was obvious that the switch was starting to fail.  I could touch the knob and the readings would change several hundred mA in the 2A range.   It was actually bad enough that I could just shake the case and have it move like this.   In my case, I just removed the PCB and cleaned it along with the contacts.  Some nice black material on the swab.  It is now stable again. 

I still like the meter and have found that 2A 1mA res to be very useful.  Its a bit too early to say how it is going to hold up with this sort of use. 

[mos6502]

ISTM that there may be a problem in the vicinity of the op-amp. I would return the trimmers to their original positions (or to their centre positions) and measure the op-amp inputs and outputs.

BTW, @Maxlor's review states that the meter should not be moved after zeroing, presumably because it will be influenced by changes in the Earth's magnetic field.

The first time I aligned the meter I followed this procedure:

After that, it worked well. Better than with the factory settings, at least.

Even when it was working, I noticed that it was much more sensitive to external influences than my expensive amp clamps - probably due to the crappy construction with the giant gaps between the cores.

But now it seems even much more sensitive than before, even the tiniest movements will result in an fluctuation of 50mA or more.

Is there a schematic for this meter somewhere? I'm not sure I want to get into tracing the schematic myself, I've already wasted way too many hours on this ...

One of mine that is also about a year old became intermittent a month or so ago.  This meter was not modified in any way.  It gets a fair bit of use but I only use the clamp function.   In my case, it was obvious that the switch was starting to fail.  I could touch the knob and the readings would change several hundred mA in the 2A range.   It was actually bad enough that I could just shake the case and have it move like this.   In my case, I just removed the PCB and cleaned it along with the contacts.  Some nice black material on the swab.  It is now stable again. 

I still like the meter and have found that 2A 1mA res to be very useful.  Its a bit too early to say how it is going to hold up with this sort of use. 

Hmm, not very confidence inspiring. I just cleaned the rotary switch with some contact cleaner ... no joy. Gonna try and clean the entire PCB now with alcohol.

[Electro Detective]

I've been wanting to get a small clamp meter that does TRMS AC and DC for small leakage currents,

especially troubleshooting RCD/GFCI trip issues without the hassle of squeezing in a usual size ma clamp inside tight rats nests 

I was going to get one of these smallish UT210E meters (against my better judgement) but now it seems I either have to look elsewhere and spend a LOT more ( = NO!  ) 

or give it a miss and get along roughing it as I have,

or buy TWO UT210E meters, and pray that either one or both work and agree,

or both die on me eventually, and I end up butchering both to slap together one sort of working one (Franken-T ?  ) 


"Help us Obi-Wan..."   

[joeqsmith]

It's been a while since I made that video showing the higher bandwidth and alignment.   I remember setting the pots was a major pain to get right.  It's very sensitive and requires that diddle stick (not a metallic screwdriver).   As you have adjusted yours, I wonder if the pots are now having problems.  There isn't much to the meter to go wrong. 

I can tell you that I know where nine of them are that were all purchased at roughly the same time.   Of these, only that one that I mentioned has had a problem.   The first two I bought for home don't see a lot of use and are still fine.  I realigned both meters but only modified the hardware on that one unit.   

There are schematics available for this meter on-line.   

I wasn't expecting much for the $30 but so far I've been pleased with them.

Someone linked it here:
https://www.eevblog.com/forum/testgear/a-look-at-the-uni-t-ut210e/600/

[beanflying]

especially troubleshooting RCD/GFCI trip issues without the hassle of squeezing in a usual size ma clamp inside tight rats nests 

I was going to get one of these smallish UT210E meters (against my better judgement) but now it seems I either have to look elsewhere and spend a LOT more ( = NO!  ) 

or give it a miss and get along roughing it as I have,

...

Mine has been accurate and works great on DC or AC current which is all it gets used for in my tool bag. Small Jaw and form factor makes it possible to go places other meters simply can't (inside coffee machines in my case with the panels on). If it saves you 5-10 minutes on site a job by not having to remove extra wires and panels and you do 5 or 6 jobs with it throw it in the bin and buy another it owes you nothing at that time unless you work for free. At least that is how I am viewing this meter in my case. The NCV is a good feature too.

Different if your tools are a hobby or home thing then you only have a frustrating paperweight left.

As to plugging it into mains I wont be 

[Electro Detective]

especially troubleshooting RCD/GFCI trip issues without the hassle of squeezing in a usual size ma clamp inside tight rats nests 

I was going to get one of these smallish UT210E meters (against my better judgement) but now it seems I either have to look elsewhere and spend a LOT more ( = NO!  ) 

or give it a miss and get along roughing it as I have,

...

Mine has been accurate and works great on DC or AC current which is all it gets used for in my tool bag. Small Jaw and form factor makes it possible to go places other meters simply can't (inside coffee machines in my case with the panels on). If it saves you 5-10 minutes on site a job by not having to remove extra wires and panels and you do 5 or 6 jobs with it throw it in the bin and buy another it owes you nothing at that time unless you work for free. At least that is how I am viewing this meter in my case. The NCV is a good feature too.

Different if your tools are a hobby or home thing then you only have a frustrating paperweight left.

As to plugging it into mains I wont be 

I hear that!    the sockets taped over and supplied cheapie? leads won't leave the wrapper and stored or recruited for use elsewhere



My app as above would be only for AC ma clamping in tight spaces

and the ocassional DC go/no go check in a circuit where I don't want to cut wires (or risk hurried meter setting blunders)

add the ocassional 'parasitic draw' hunt in family/friends vehicles that we all love to blow a casual Saturday/Sunday afternoon on 
oh well, the beer and pizza is free at the end of it, and everyone happy
as long as the meter doesn't get dropped hard or driven over...     


For my purposes two of these may be the way to go, and still be cheaper than a decent cheap clamp meter
that may not go down as low as this niche gadget UNI-T clamp.
I can deal with the DC "zero out/don't move the meter" thing, I do that anyway with other clamps to get a steady come reliable reading

They may even last a while if I'm lucky (yeah, right... ) best I can do is keep packed in a Pelican foam lined case
with batteries removed after each use,
and pray I didn't cop two units from a Friday production batch 

anyways, hope OP gets his sorted asap

[mos6502]

It's been a while since I made that video showing the higher bandwidth and alignment.   I remember setting the pots was a major pain to get right.  It's very sensitive and requires that diddle stick (not a metallic screwdriver).   As you have adjusted yours, I wonder if the pots are now having problems.  There isn't much to the meter to go wrong. 

I can tell you that I know where nine of them are that were all purchased at roughly the same time.   Of these, only that one that I mentioned has had a problem.   The first two I bought for home don't see a lot of use and are still fine.  I realigned both meters but only modified the hardware on that one unit.   

There are schematics available for this meter on-line.   

I wasn't expecting much for the $30 but so far I've been pleased with them.

Someone linked it here:
https://www.eevblog.com/forum/testgear/a-look-at-the-uni-t-ut210e/600/

Thanks for the schematic! I'm a bit blown away that one exists. I'll attach it again so it's easier to find. Anyway, I did a bunch of measuring and everything seems fine, except: VR4 measures at 218 ohms instead of 500, VR+ measures at 3.24k and VR- at 3.21k instead of 5k. With the FPC connector disconnected, I'm measuring 452 ohms for VR4 and 6.45k and 6.27k for VR+ and VR-, respectively. Can anyone confirm if these values are still in spec?

Oh yeah, I'm using one of these for adjusting the pots:

[joeqsmith]

I would suspect the wiper's contact to the substrate, not the resistance across the substrate.  You may not be able to check them in-circuit.  Maybe just try adjusting them and seeing if the meter jumps.  I would be looking at mechanical problems first. Ribbon cable and connector, solder....   Maybe an outside influence (some sort of field).   

If you have a scope, you could track it down fairly quickly.  I would just inject an AC signal and watch the output of the instrumentation amp and see how it behaves. 

Yes, that is the tool you want to use. 

Someone posted a recent review of this meter.  I always enjoy how they randomly point at parts and ID them.   The quad op-amp is apparently the LCD driver and several resistors are diodes.  Rare I post a comment.  Looks like he blocked it. 

https://youtu.be/0WLpc0mfYi0?t=995

[mos6502]

I see, I was thinking that the substrate of the pots might have worn away or something. The pots seem to work fine and I can adjust the reading smoothly over the entire range, so I'm not sure. I do have a couple of scopes and an old HP3311A function generator. What sort of signal would I be injecting and where? Sorry, I'm not really an analog guy.

Is it possible that the hall sensors got damaged somehow? Now that I think about it, the meter did see >300 amps somewhere around the time it was last working.

[joeqsmith]

LOL!!  One of the first things I did when I got one of these meters was put it on the MIG welder and struck an arc.  That was pretty much the end of the meter.  After that it would only display OL.

I doubt the sensors would be damaged unless you were drop testing it on the clamp.  These things are held together fairly well and I assume you made no attempt to open yours. 

I would just wrap the head with several turns of wire and inject some amount of AC current. You should see the signal at the output of the LCD driver IC.     In that video, I show one place you could measure at.   Make sure it's not distorted and the ranges all work.   

Keep in mind it's $30 as well.  But the learning experience may be worth that alone. 

[fzabkar]

Please excuse my ignorance, but there are two Hall effect sensors in the circuit diagram. Are these installed at each end of the stationary jaw, presumably in anti-phase? Is this how the earth's magnetic field is nulled?

Does anyone have a datasheet for a suitable sensor? I can't find any that operate from an 0.8V supply.