Good clamp meter for low DC currents

[HKJ]

I may have misinterpreted the description of the Benning that I linked to, which is why I deleted my previous question.
If I managed to understand correctly, then a
The uA measurement does not apply to the clamp meter...
The clamp meter measures with a minimum scale of 10mA.

Clamp meters measures the magnetic field around a wire and calculates the current from that, when measuring DC the earths magnetic field is a issue for low current measurements.

For that reason most clamp meters works with resolutions of 0.01A or worse, but there are a few meters with better resolution, many of them they are not really more precise and the extra digit is hard to get any reliable information from.

A few like the above Fluke and above Benning are made to really work at low current, the Fluke with 0.01mA resolution and the Benning with 0.1mA resolution. I do not know much above the Fluke, but the Benning can be used to see current a bit below 1mA (it requires careful use).

A few clamp meters has regular DMM shunt for low current measurement, the above do not, but uses the clamp.

[Martin72]

The Owon sounded so interesting to me that I ordered it and it should arrive tomorrow.

Actually arrived today.
I still have the UT210e, so it will be easy to compare.
First impression of Owon after unpacking:
Good touch quality, I wouldn't have thought.

[Martin72]

Clamp meters measures the magnetic field around a wire and calculates the current from that, when measuring DC the earths magnetic field is a issue for low current measurements.

It would be better if they were equipped with the current compensation method, which increases a current through a winding on the core until the difference to the measured current is 0.
These current clamps can then also be easily demagnetized; they have a corresponding function for this.
But unfortunately this is not feasible in such price ranges, perhaps the fluke in question has this in order to be able to measure so sensitively at all.
In any case, the Owon showed an "insane offset" when you switch to DC - I find over 300mA intense.
You can zero it with the "Zero" button, but that only conceals it.
I have now taken a few measurements, preferably in the lower mA range, pictures are currently being prepared.

[Martin72]

Here are a few measurements, which I will soon make a little more detailed (other currents, voltages, resistance, etc.), possibly in a new thread.

[csuhi17]

In any case, the Owon showed an "insane offset" when you switch to DC - I find over 300mA intense.

I have 6-1 of these, I could have left one
At 2A, I have an offset from -150mA to 600mA.
But the measurement is not affected.

[wasedadoc]

There are two quite different situations:

1.  The clamp meter is in a fixed position and the current can be turned off when zeroing.

2.  The current cannot be turned off, so the clamp meter must be in different places when zeroing and measuring.  Even worse is when the meter is being handheld.

[Kean]

I may have misinterpreted the description of the Benning that I linked to, which is why I deleted my previous question.
If I managed to understand correctly, then a
The uA measurement does not apply to the clamp meter...
The clamp meter measures with a minimum scale of 10mA.

Yes, it isn't at all clear from the CM 10-PV data sheet.  After looking at the user manual it shows the only range that uses the clamp meter is the Amp range.  All other measurements including the microamp range require using the probes.

As mentioned above the Fluke 771/772/773 clamp meters have a 10uA resolution but have a limited range to 110mA.  They are specialist meters for process control and priced accordingly.  The Kyoritsu 2500 is similar with 10uA resolution and max 120mA.  I bought my Fluke 771 many (~10) years ago, and apart from my Tek scope it was one of the most expensive pieces of test equipment I owned at the time.  I still have it and it still works fine.

The only handheld microamp resolution clamp meters I have come across are for AC leakage measurement, but there may be some specialist ones I haven't seen.  I have the UT251A which measures up to 60A AC, but has a resolution of 1uA.  I believe it is 6000 count, so max 6mA at that resolution.

The best way to do low current measurements with a clamp meter is to pass the wire being measured through the clamp multiple times, but that isn't always practical and still doesn't come close to the resolution you can get by inserting a current shunt into the loop.

I own a few of the UT210E clamp meters, but I find their readings are inconsistent.  One in particular needs calibration as it has a large offset that I can zero out but otherwise cannot remove even with careful degaussing.  I also have a couple of TENMA IN05268 clamp meters with a 1mA resolution, and while they are more expensive than the UT210E, they are my preferred DC clamp meters.

Yes, I own a few meters... 

[Martin72]

A few...

I have now compared the two with DMMCheck Plus.
The Owon not only has 20000 instead of 2000 counts, but also frequency measurement and duty cycle.
Neither of them can measure voltage with 10kHz AC.
But that's not what they are designed for.
Should I continue here or should I open a new thread?

[Kean]

Should I continue here or should I open a new thread?

I suggest continuing here.  A search will find the posts either way.

I will try do some similar comparisons later today of a few of my clamp meters against my Advantest R6142 and Keysight 34465A.

[HKJ]

Yes, it isn't at all clear from the CM 10-PV data sheet.  After looking at the user manual it shows the only range that uses the clamp meter is the Amp range.  All other measurements including the microamp range require using the probes.

I do not know about the CM10-PV meter, I only talk/write about the Benning CM11 meter.

As mentioned above the Fluke 771/772/773 clamp meters have a 10uA resolution but have a limited range to 110mA.  They are specialist meters for process control and priced accordingly.  The Kyoritsu 2500 is similar with 10uA resolution and max 120mA.  I bought my Fluke 771 many (~10) years ago, and apart from my Tek scope it was one of the most expensive pieces of test equipment I owned at the time.  I still have it and it still works fine.

Working low current DC clamp meters are expensive.

The only handheld microamp resolution clamp meters I have come across are for AC leakage measurement, but there may be some specialist ones I haven't seen.  I have the UT251A which measures up to 60A AC, but has a resolution of 1uA.  I believe it is 6000 count, so max 6mA at that resolution.

Measuring low AC current is not that hard, the earth magnetic field do not change fast, i.e. it do not affect AC measurements.

The best way to do low current measurements with a clamp meter is to pass the wire being measured through the clamp multiple times, but that isn't always practical and still doesn't come close to the resolution you can get by inserting a current shunt into the loop.

Using multiple turns in the clamp can make any clamp meter good at mA or even uA range with enough turns.
Measuring low mA or uA DC current with a clamp meter is not common.

I own a few of the UT210E clamp meters, but I find their readings are inconsistent.  One in particular needs calibration as it has a large offset that I can zero out but otherwise cannot remove even with careful degaussing.  I also have a couple of TENMA IN05268 clamp meters with a 1mA resolution, and while they are more expensive than the UT210E, they are my preferred DC clamp meters.

The UT210E is a fairly good low cost meter at low currents and one I will recommend for hobby usage, but if you really need to measure a few mA with a clamp meter, the Benning CM11 (or similar, like Fluke) is the answer.

Yes, I own a few meters... 

Who doesn't.

[Martin72]

I suggest continuing here.

OK...

Here is a table with the values, on the far left are the actual calibrated values from DMMCheck Plus.

I like the Owon better, currently.
It could be the successor to the UT210E as a low-cost clamp meter, with higher resolution and slightly more functions.

[DaneLaw]

If I recall the Owon CM2100/B had a tendency to drift alongside a heavy offset, and with a very barebone input protection close to non-existent, but that is Owon meters in a nutshell..
but like always with these cheap meters.. it can vary a lot from unit to unit and how lucky you are in that lottery.

but cheap clamp meters with 1mA DC resolution, are a dime a dusin these years and can be had for around 25 euro and up.
even AC+DC clamp units with 1mA DC & 0.1mA AC on the clamp is from 30 euro and up (incl. delivery and 25% EU VAT)
but none of them seems optimized for low current with a small gap/eye, so the performance will likely be around the norm, as we see with the likes of 210E & co.

[Martin72]

If you really need accuracy in the mA range, you unfortunately have to spend money, you can't have certain things cheaply.
I still like the Owon better than the Uni-T, but that shouldn't cloud the fact that we're talking about 40€ devices here.
I think you can expect something "serious" from the Benning onwards.

[BILLPOD]

Well Martin, at least you got batteries with yours   And I sprung for the model with Bluetooth, as I have a penchant for meters with it.   My comparison was not exacting as yours, but my UT210E and CM2100B ran neck in neck, always within a couple counts, (least significant digits).
I find the bluetooth app is better than most of my other BLE meters,
as it has multiple recording options.  I'm going to put my UT210E in the Owon pouch and keep it in my vehicle and keep the Owon on my bench,
or within easy reach. 

[Kean]

Sorry that I didn't get a chance to run these tests last year... but here are the results.

I've attached the spreadsheet of comparison data in PNG and CSV formats.  I skipped recording a few results where they were not meaningful.

For the Fluke 771 with currents below around 1mA it could take about 10 seconds to settle, but did a pretty decent job.

I ran the tests twice to verify they came back much the same.  I also experienced a power failure in the office while doing this, so I ended up having to redo half of it a third time.  I tried not to move anything, but I am sure there was some drift during the hour this all took.

Forgot to mention here, that the current source was my Advantest R6142.  Also, none of my gear has recent calibration - but my 34465A, 34401A, and 34972A all agreed within a few counts when last compared.

Happy New Year!

[Martin72]

Thank you, it could hardly be any clearer...
Then I'll test the Benning CM11 at work next week.

[Martin72]

Well Martin, at least you got batteries with yours

And a screwdriver !

[Kean]

Thank you, it could hardly be any clearer...

I was a bit surprised at the final results in the 1-5mA range, as I didn't expect them to read so close to the actual value.  I did have to re-do the zero a couple of times to get them stable at the start, and again when they did an auto power off twice mid-way through all the measurements.

My UT210E #1 device has a note on it that it was not reading stable values when I used it in early November, but it came good after cycling the range switch a few times.  The other two UT210Es have a note that they read low, which matches the results.  I bought these UT210E's on ebay from a Chinese seller back in 2017.

ST-337 #1 (aka TENMA IN05268) has been my go-to clamp meter.  I hadn't noticed that ST-337 #2 was also reading more than 10% low.  I bought these both from Element14, one in 2009 and the other in 2012.  From the serial numbers, it looks like #1 is actually the older one.  These each cost more than all three of the UT210Es.

I can't find a record, but it looks like I probably bought the Fluke 771 back in 2008 at the RS trade counter.  That would make sense as 2008 is when I started doing my electronics consulting business.  Back then it would have cost close to 20x the price of a single UT210E bought nearly 10 years later, and is still at roughly the same multiplier now.

If the Benning CM11 was available in Australia, and was available for less than 10x the cost of a UT210E, then I might consider getting one of those as well.   

[BILLPOD]

I got the screwdriver, but no batteries, which is no biggie, as they are probably junk alkaline that would leak and ruin the meter.  I put in a pair of Nimh, but I don't think they will last long, as supposedly the meter cuts out at 2.2 volts.  I am considering lithium primaries, but wonder how the higher voltage will play out

[Kean]

The OP hasn't replied at all, so I'm wondering if they got the answer they were after... or just have more questions...

They've been active on the forum since starting this topic, and even the last few posts, but not actually posted anything new.

[KlausF]

After 2 years, my UNI-T 210E suddenly does not function any longer, DC amps is defective, I would say for no reason. It was rarely used and if it is was, then only indoor and for low currents. Cheap Owon CP2100 looks like UT210E, I want something better. Any suggestions ? What would be a good alternative for let´s say up to 400 bucks ?
I was about to get me a Benning CM 11, but its "performance" is not what I am looking for.

[HKJ]

After 2 years, my UNI-T 210E suddenly does not function any longer, DC amps is defective, I would say for no reason. It was rarely used and if it is was, then only indoor and for low currents. Cheap Owon CP2100 looks like UT210E, I want something better. Any suggestions ? What would be a good alternative for let´s say up to 400 bucks ?
I was about to get me a Benning CM 11, but its "performance" is not what I am looking for.

I have not looked at the video, but in my experience it is way better at low current then the 210E (I have both).
For clamp meters I have two groups: Low DC current and general purpose. CM11 wins in low DC current, but for general purpose it lacks high current ranges. Because I work with electronic I mostly need low DC current measurements, this makes CM11 my favorite clamp meter.

[Martin72]

I have not looked at the video,

I looked at it, a bit hair-raisingly done...
The biggest disadvantage of the CM11 is that you have to be very careful not to overrun it in terms of current.
If you keep this in mind, it is very suitable for small currents.

[HKJ]

I have not looked at the video,

I looked at it, a bit hair-raisingly done...
The biggest disadvantage of the CM11 is that you have to be very careful not to overrun it in terms of current.
If you keep this in mind, it is very suitable for small currents.

I have still not looked at it, but if the issue is that the clamp get magnetized at higher current, I do not see that as a serious issue.
I played a bit with it here: https://lygte-info.dk/info/DMMClampDemag%20UK.html

[Martin72]

First, a mixed current is measured (direct rectification without an electrolytic capacitor) and it is wondered why the display jumps back and forth.
Then at some point the CM11 is connected between a load and the supply and it is criticized that it is reasonably accurate - with regard to the values displayed at the load and the supply and other errors.
A somewhat adventurous "review".