High Resolution Clamp Meter for Current Measurement

[VanIsleDSM]

Until a few years ago clamp-on meter resolution only allowed you to measure to the nearest 100mA, which is no good for power LEDs and such, but recently meters have advanced as far as allowing a 0.1mA resolution, negating the need to measure the voltage across current sensing resistors to check current.

Now you don't even need to break the loop to check, just clamp one of these meters on.

I'm wondering if anybody has tried this meter:

http://cgi.ebay.ca/Clamp-Meter-with...emQQptZLH_DefaultDomain_0?hash=item1c0d60f1b3

It's very well priced, and claims to measure down to 1mA AC/DC, perfect for what I want. The 3 digits concerns me though, how is it supposed to show 4A down to the closest mA with only 3 digits?

If anybody has tried this meter out, or has a suggestion for another one, I'd love to hear about it.. if not, it's cheap enough, I'll probably just order it and see what it's like.

Thanks!

 

[SirJMD]

- Ebay
- "High quality"
- Good price

Three things thats usually a warning sign.


I really doubt that it will be able to meassure DC current with the clamp! Im quite sure that you need to use the banana-plugs. The reason why a clamp works for AC, is because of the changing electromagnetic field.

EDIT: typo.

 

[VanIsleDSM]

I'm well aware of the concerns with Chinese merchandise, I know it's not going to be quality like a fluke meter, but as long as it does what is advertised to do, that's all I care about, it's not going to be used in a harsh working environment.

I will obviously double check the accuracy with a current sense resistor to see what it's like, just thought I would ask to see if anybody else has used this meter, or another like it. Lets keep it on that topic.. not the reliability of Chinese merchandise.

 

[65535]

My concern would be just that, it probably won't do what it is advertised to do, or not accurately. If you are willing to try it out go for it. Do they have a good return policy?

 

[VanIsleDSM]

Well.. I bought it, I guess we'll see how it works.

I could have spent $300+ on the EXTech unit, which I will probably end up doing if this one is a dud, but for the price.. I'm too intrigued not to try it out.

I looked into the company that makes it, and they're small, but seem decent:

"Based on over ten years experience,standing ahead the modern technology,our R&D department design all the products under the requirement of IEC-1010.All of our products are qualified with CE(LVD & EMC)safety standards and ISO9001-2000."

I'll test it out and let you guys know how accurate it is.

 

[Mr Happy]

That meter has a 3,999 count display. Which means that on the 4 A range it can read up to 3.999 A, which is 1 mA resolution as it claims. However, do not confuse resolution with accuracy. The accuracy is given as 2.0% of reading ± 3 digits. So if the meter reads 0.500 A (500 mA), you can expect the actual current to fall in the range of 500 mA − 2% − 3 mA = 487 mA and 500 mA + 2% + 3 mA = 513 mA.

That's probably the best accuracy though. If you do not measure current in a long straight wire with no stray magnetic fields around you can expect the accuracy to be worse.

However, the price does look good compared to some other meters costing $100's, so do let us know how it works out when you receive it.

 

[digitor]

I really doubt that it will be able to meassure DC current with the clamp! Im quite sure that you need to use the banana-plugs. The reason why a clamp works for AC, is because of the changing electromagnetic field.

EDIT: typo.

DC clamp meters have been around for a long time - they use the Hall effect to measure DC currents, and can be quite accurate.

Cheers

 

[VanIsleDSM]

Indeed they have been around for a while, I have one that has a 400A and a 1000A setting that I use for checking the current on welding machines at work, but it's only good to the closest 100mA, not 1mA like this one.

The 3 and 3/4 digit thing was confusing me, as usually that means 3 digits, with a 1 in front, and a -/+. Somehow I didn't notice the 3999 counts, thanks Happy!

I would think the accuracy readings would be worst case, and as with most tolerance specs they leave themselves some room on either side, and it usually falls somewhere in the middle, but I'll definitely check it out.

Funny thing is, the EXTech expensive meter that's similar, it's also +/- 2.0% +/- 3 digits, and I ended up going with a slightly better Kilter meter than I first posted, that is only 1%, so my readings on 500mA could be 492mA - 508mA, completely acceptable if it ends up working as claimed.

 

[Frank E]

Most clamp meters are 2-3% accuracy on DC A and top of the range meters eg a Fluke 902 give 1%. A good hall effect plug in hall effect current clamp would also give about 1% but you'd have to factor the uncertainty in the meter and the uncertainty in the clamp..
To get any better accuracy with resolution on a handheld that on a dc clamp you are looking at a loop clamp calibrator which will be a resolution of0.01mA accurate to 0.2% or 5 counts but you would be limited to 4 to 20mA range
That would be a total waste of money. If you want to check the accuracy, send the meter to a calibration lab, I think the quoted accuracy is fine for the application.

 

[VanIsleDSM]

Most of the inaccuracy will come from the drift in the hall effect sensor seen from temperature change. How well that is compensated for will make the biggest difference.

I don't think I need to send it to a calibration lab to check the accuracy, I'll just check it against using a current sense resistor to see how how far off it is.

 

[SirJMD]

DC clamp meters have been around for a long time - they use the Hall effect to measure DC currents, and can be quite accurate.

Cheers

Ah yeah, of course. Ive even read some articles on such ICs.


As for the accuracy: What about using a good multimeter/ammeter in series with whatever youre drivining, and then see what the clamp meassures - and compare those two.

 

[jhellwig]

Even the fluke dc mA clamp meters are not to great of resolution for electronic circuits.