Current clamp problem

[russellr]

Hi,

I have am AC current clamp that outputs 1mV a.c for each 0.1 Amp a.c.

The instructions say to set the DMM to the 3V a.c. range.

Here's my problem: neither of my DMM's have a range close to that - they both start at 200 VAC.

As a result, no measurement is useful.

Help please!

Can I:

1. Add in a resistor before the DMM connection to multiply the voltage? If so, how would I figure out the right value?
2. Buy a cheap $10 DMM on eBay and expect to get reasonable measurements? I'd be happy with 0.5 amp accuracy.

thanks,
RR

 

[KeepItSimpleStupid]

1. Add resistor, no
2. Yes.

Current clamps usually need to be zeroed. Most of the accuracy will depend on the clamps specifications.

 

[squishy36]

You might want to buy a more suitable multimeter. My 20+ year old Fluke 83 has AC ranges of 0.4, 4, 40, 400, and 1000 V -- and I find I use all of them a lot.

Also note that your measurement accuracy will probably be substantially less than the DC measurement accuracy the marketers love to stick in your brain. Typical multimeters have AC accuracies of 1% to 3% or even worse. The composite measurement might have e.g. a 5% measurement accuracy. You might also need to worry if the current waveform you're measuring is not sinusoidal -- even if the meter is an RMS meter, check the bandwidth, as the cheap meters have cheap bandwidths.

 

[crutschow]

Resistor networks can only attenuate, not amplify (multiply).

I didn't see any cheap multimeters on ebay with a low AC range. You may have to buy a slightly better one with low AC ranges such as this from Harbor Freight which has a 2V AC range.

 

[kiriakos-gr]

There is no chance to operate an Current clamp probe with a cheapy DMM.

Accuracy comes mostly from the DMM it self.
It should have also 10Mohm impedance, plus low AC range,
you do not need much, just one Agilent U1272A.
Read the review here.. agilent-u1272a-review-kiriakos-triantafilloy-greece.html

The specific DMM got the most of the admiration, because it is the " best ever " about operating with Current clamp probes.
Read about the scale function, so to educate your self.

 

[SABorn]

If all you need is a low resolution AC amp reading then its cheaper to buy a complete tong meter with the built in display and a small multimeter built into it off ebay for around $10.00, i have one and it works quite well, it is also more accurate then the multimeter addon one i have.

Something like this one.