Which Clamp Does This?

[Randy222]

I am looking for an AC/DC amp clamp, but one that is better suited for say 10A or less, and can accurately read to 1mA.
Category of sub $100(US) $75(GBP)
Suggestions?

[BILLPOD]

Good Morning Randy222, I have both, the UniT UT210E and the OWON CM210B.   They are both in your price range and both are similar in specs, but the Owon has Bluetooth, which is why I also bought it.   They both measure down to the low mA with accuracy that meets my requirements.   Several threads, here on The Forum about both.

[Aldo22]

I am looking for an AC/DC amp clamp, but one that is better suited for say 10A or less, and can accurately read to 1mA.
Category of sub $100(US) $75(GBP)
Suggestions?

It depends on what you mean by “accurately read to 1mA.”
I have the OWON CM2100B and am very happy with it.
It has a resolution of 1mA.
If you need to know 1mA very accurately, you would probably need a resolution of 100µA or better.

[Martin72]

   Several threads, here on The Forum about both.

https://www.eevblog.com/forum/testgear/good-clamp-meter-for-low-dc-currents/

Even on the first page here...

[Randy222]

I went with a UT210e, the 1mA resolution is ok for my need.
The UT211b has nice specs, but price is too high, about 3x that of the 210e, and, 0.1mA resolution is on AC.

In the other thread the DM-268B WINAPEX DC AC 0.1mA High Precision Clamp Meter  is touted, BUT, read the specs, it's only 0.1mA in AC, and 1mA in DC. The UT210e is less $$ for DC 1mA.

I see sub 1mA resolution for AC. I found one that was a really great price, but it was AC only amp clamp (and no dvm stuff). Finding sub 1mA for DC is not cheap.

[Randy222]

It depends on what you mean by “accurately read to 1mA.”
I have the OWON CM2100B and am very happy with it.
It has a resolution of 1mA.
If you need to know 1mA very accurately, you would probably need a resolution of 100µA or better.

If I want to see down to 1mA then we need at least resolution to 1mA, even if accuracy is not that great. It might show 0.001A but actual might be 0.0014A or even 0.0009A. Wouldn't make sense to have a screen that was 000.00000A yet resolution was 0.02A. I mean it could be, but why would I need two trailing zeros all the time.

However, if the meter is accurate to 1mA then we should expect resolution to be at least 1mA. Wouldn't make much sense to pay for a 1mA accurate meter if the display was at best 000.0A

Did I get that right?

[Aldo22]

Did I get that right?

Both clamp meters (Uni-T and Owon) have an accuracy of ±(2%+8dig) in the lower DCA range.
This means that the last digit can fluctuate by ±8mA due to the ±8dlg alone.
So if you want to be sure that 1mA and not 2mA is present, this is not accurate enough, even if it's not quite as bad in practice.

[Martin72]

The problem is that neither the Uni-T UT210E nor the Owon CM2100 are suitable for accurately measuring currents in the lowest mA range.
It would be too good to be true to get high-precision measuring instruments for just a few euros or dollars.
But hope never dies, which is why such products always have a chance on the hobby market.

The lowest range for both current clamps is 2A.
That is 2000mA, which, when you think about it, might give you an idea that you cannot measure small currents accurately with them.
Yes, both devices have a resolution of 1mA = 0.001A – but that does not mean that they are accurate up to that point.
For both models, accuracy in the 2A (DC) range is specified as 2%, +8 digits.
With AC current, it's a little more.
That's not particularly accurate anyway, but it's OK for the price range.
But the point is something else: the digits.
+8 for DC, +10 for AC – and the last digit is the 1mA position.
In other words, the last digit is a gamble with both current clamps.
If you want to reliably measure currents in the low mA range, the measuring range must be at least 200mA, not 2A.

Edit Aldo was faster

[Psi]

Just remember you have to press the cal/ref/zero button to zero the readings on clamp meters, especially low amp ones. The environment around them changes the readings so zeroing is compulsory unlike a normal meter. 

So take that intro account if the speed of taking readings is important.

[Aldo22]

That may now sound worse than it is.
If you consistently zero it, you can work with it.
But you have to expect fluctuations of around 1-3 mA.

[Randy222]

210e
2%+3 on DC amps (it's not +3dig)

10mA reading could be 6.8 to 13.2mA actual
That's technically +- 32% ! That seems pretty dismal.

[KungFuJosh]

If the difference of 1 or 2mA matters to you, then you need to go up in budget. You might consider buying two meters. 1 for the low mA readings with higher accuracy, and another if you need to go up to 20A or whatever. Higher accuracy in low mA/uA ranges usually comes with a lower current range.

[Aldo22]

210e
2%+3 on DC amps (it's not +3dig)

The manual states ±(2%+8dig) for the 2A range.
https://static.eleshop.nl/mage/media/downloads/UT210E_manual.pdf

My practical experience with the CM2100B is significantly better, but it is certainly not accurate to the mA.

[Randy222]

210e
2%+3 on DC amps (it's not +3dig)

The manual states ±(2%+8dig) for the 2A range.
https://static.eleshop.nl/mage/media/downloads/UT210E_manual.pdf

My practical experience with the CM2100B is significantly better, but it is certainly not accurate to the mA.

This buy is my 2nd meter for lower amp measures, I already have a General 600A (dvm amp clamp) for electrical & hvac use. It has useful inrush capture making evaluating motor starts easier for diagnostics.

I looked up (again) accuracy nomenclature, when it's written just "+3" (no dig) that usually means 3 units of the range min reading.

8dig? It's only a 4dig display. What does +8dig represent on a 0000mA or 0.000A (2A range) scale?
Do you just add the 4dig to end, so that 4dig display would be 0000.0000mA where 8dig is 0000.0001mA ? So 1/10000mA.

+-(2%+1/10000) on a 0000mA display is basically 2% = +-0.02mA , heck, anything +8dig on a 4dig display makes the "+" almost meaningless.

Also, website and manual shows deviations not using "dig", so I am confused as to what they mean, for both site page and manual.

Do they mean to say "dig"? I suspect they do.

[Aldo22]

It's about the last digit.
In this case, ±8 means that, for example, 8mV is displayed as something between 0mV and 16mV (plus the % deviations) afaik.
In practice, it's not that inaccurate for me, but those are the specifications.

In the end, the fact is that you cannot reliably distinguish between 1mA and 2mA with these devices.

[Randy222]

It's about the last digit.
In this case, ±8 means that, for example, 8mV is displayed as something between 0mV and 16mV (plus the % deviations) afaik.
In practice, it's not that inaccurate for me, but those are the specifications.

In the end, the fact is that you cannot reliably distinguish between 1mA and 2mA with these devices.

Your example is what I said earlier, w/o the "dig" part usually means units of least significant in display. Hence "+3" is different than "+3dig"

+3dig on say the 20A range in a 4dig display is not the last dig, it's the 3rd dig, or .1A
The 100A scale can display 000.0A, so 3rd dig here is 1A.

If I am reading what "+8dig" means correctly, on a 0000mA display, the device has 1/10000mA sensitivity on that range but can only display down to 1mA (4dig). The device has to use a rounding method, assume 1/2 up/down, 5000*1/10000 could round up to 1mA, 14999*1/10000 could round down to 1mA.

[Aldo22]

Hence "+3" is different than "+3dig"

Where did you get the idea that this is something different?
I'm not aware of that.
Neither are the spec sheet writers, apparently, since they don't make any distinction.

[Bobson]

You can spool 10 turns of wire around one of the jaws and get 10 times the value.

[Aldo22]

You can spool 10 turns of wire around one of the jaws and get 10 times the value.

Yes, but it's usually difficult without interrupting the circuit.
And if you have to do that anyway, it's better to use a normal DMM for mA and μA.

[Randy222]

Hence "+3" is different than "+3dig"

Where did you get the idea that this is something different?
I'm not aware of that.
Neither are the spec sheet writers, apparently, since they don't make any distinction.

If we agree Uni-T manual is using wrong notation, that it should be +8dig, and the meaning is 8 counts of least significant, 8 counts of LSD in the 0000mA scale means the the meter is basically useless until real amps get closer to 800mA because +-8mA from 800mA falls into 1%, Any real amps less than 800mA and the total error goes well above 1%. Hence the meter is more like a 000.0A meter up to 100A,

There's certainly a diff in the meanings. +8 (units) vs +8dig (8 counts of LSD). Specifically for 0000mA display, the error is the same at 8mA.

But if I go by (use) the definition as defined below, +8dig on a 0000mA display says the extra error is 8 counts of the least significant value in the 4dig display, here being 1mA. Thus 2%+8dig would be +-(2%+8mA).

If we use counts of least significant, on the 0000mA display, 1mA reading could be +-(0.02mA +8mA), 8 counts of 1mA, meaning actual current could be in range of 0-8.02mA and meter would still just show 1mA. On the high end that is 800% error.

If it were 00.00A scale on display , +2 is 2A, +2dig is 2 counts of LSD, or 2x 1/100A.


Ref: https://www.designworldonline.com/how-to-determine-digital-multimeter-accuracy/

Understanding Accuracy Specifications
Accuracy Definitions

    (2% + 3): This means the accuracy of the measurement is ±2% of the reading plus an additional error of 3 units. For example, if the reading is 100 volts, the accuracy would be calculated as follows:
        2% of 100 = 2 volts
        Total accuracy = ±2 volts + 3 units = ±5 volts
        Therefore, the actual value could range from 95 to 105 volts.

    (2% + 3 digits): This specification indicates the accuracy is also ±2% of the reading, but the additional error is expressed in terms of digits. Here, "3 digits" means the error can be ±3 counts on the display. For instance, if the reading is 100 volts:
        2% of 100 = 2 volts
        Total accuracy = ±2 volts + 3 counts (assuming counts refer to the least significant digits, like 0.001 volts)
        If the meter has a resolution of 0.001 volts, the total accuracy could be ±2.003 volts, meaning the actual value could range from 97.997 to 102.003 volts.


Key Differences
Specification   Calculation Example   Total Accuracy Range
(2% + 3)   ±2% of reading + 3   Wider range (e.g., 95 to 105 volts for 100 volts)
(2% + 3 digits)   ±2% of reading + 3 counts   Narrower range (e.g., 97.997 to 102.003 volts for 100 volts)

In summary, the main difference lies in how the additional error is defined: as a fixed unit (3) or as a count of digits (3 digits), which can lead to different ranges of accuracy depending on the reading and the meter's resolution.

[Aldo22]

If we agree Uni-T manual is using wrong notation

Most manufacturers write ±(x%+y).
Even if your distinction is correct, which I find hard to believe, it is irrelevant if no one adheres to it.

[Randy222]

Most manufacturers write ±(x%+y).
Even if your distinction is correct, which I find hard to believe, it is irrelevant if no one adheres to it.

Seems to be mixed bag vs "most". I think the use of word "dig" means something different than w/o it.
Maybe they all mean to say "dig"?

Ref: https://files.owon.com.cn/specifications/OWON_35_Digital_Multimeter.pdf

[Randy222]

UT210E showed up today. Did not know about the geometric zero'ing crap-ola requirement.

Manual says the zero'ing must be done in the position used to make measurement. So I guess that explains it. Such weirdness for using it makes it a bit difficult to use as a mA DC clamp.

I'll run my own mA tests, but trying to keep an amp clamp in same orientation as zero'ing is a bit absurd for practical use.

I also ordered up the OWON CM2100, adding to my glut of meters. It too (manual) says exact same thing for zero'ing DC amps.

Low budget items give low budget features.

[Aldo22]

Did not know about the geometric zero'ing crap-ola requirement.

These clamp meters use a Hall effect sensor for ADC, which also reacts to the Earth's magnetic field and other magnetic fields.
https://en.wikipedia.org/wiki/Hall_effect_sensor

Zeroing helps to counteract this. However, this should be redone for each environment.

[Randy222]

An interesting vid worth watching.
The UT210E was the only one that did accurate measurement of DC clamp amp down to 1mA.

The 20000 count of the Owon didn't seem that helpful.