Simple clamp ammeter - Page 1
Forum section: electronics / testgear

author: Rachie5272
author_rank: Regular Contributor
timestamp: October 12, 2013, 02:59:09 am
content: I'm looking for a clamp ammeter to use for a science demonstration. I'm going to be rewiring a microwave transformer as a high current power supply, and need a way to measure it. I'm expecting somewhere around 100-200 amps AC, but 1000 amp capacity would be nice for paralleled transformers.Can anyone recommend one? Is it feasible to get something half decent in the $50 range? Accuracy isn't the greatest importance, and safety isn't a big concern with clamp meters, but many of the reviews I've read have been terrible.Can any of these meters give a power reading as well, using the leads to measure voltage? I can live without it, but it would be nice.

author: skipjackrc4
author_rank: Regular Contributor
timestamp: October 12, 2013, 03:29:02 am
content: You could go for a Fluke Y8100 on eBay. It's just the clamp--you need to use another volt meter to get a reading. However, they work pretty well. I think I paid $30 for it about a year ago for mine. Others may chime in with more integrated solutions.

author: Wytnucls
author_rank: Super Contributor
timestamp: October 12, 2013, 03:42:29 am
content: I would recommend the UT 231, if you can't find anything cheaper in the States. 10,000 count TRMS.It does power and is good up to 1000A AC. I doubt you will find something for 50$ with those features, unless it is a well used second-hand clamp. You also get internal data logging (99) and USB interface, as a bonus.180$ deliveredhttp://www.ebay.com/itm/UNI-T-Digital-Power-Clamp-Meter-UT231-/390305496144?pt=LH_DefaultDomain_0&hash=item5ae0053c50

author: Wytnucls
author_rank: Super Contributor
timestamp: October 12, 2013, 04:00:26 am
content: Other cheaper options:UT202A 600A AC, no power measurements, not TRMS:24$ free shippinghttp://www.ebay.com/itm/Uni-T-UT202A-Digital-Clamp-Multimeters-DMM-DCV-ACV-TEMPERATURE-/221132859546?pt=LH_DefaultDomain_0&hash=item337c8ba89aUT205A 1000A AC, no power measurements, not TRMS:47$ free shippinghttp://www.ebay.com/itm/UNI-T-UT205A-UT-205A-Clamp-LCD-Digital-Multimeter-Current-AC-DC-Tester-Meter-/171073439622?pt=LH_DefaultDomain_0&hash=item27d4c58786UT207 1000A AC, no power measurements, TRMS:140$ free shippinghttp://www.ebay.com/itm/True-RMS-Clamp-Multimeter-DC-AC-1000A-600V-66M-ohm-66MHz-Surge-Current-UT207-/300985185622?pt=LH_DefaultDomain_0&hash=item46141d7556

author: Rachie5272
author_rank: Regular Contributor
timestamp: October 14, 2013, 09:59:39 pm
content: The UT 231 looks tempting, but it appears to have a horrible user interface.I forgot to mention, DC current is somewhat important, since I might be using lead acid batteries for power in some cases. I'm making a marinov motor, if anyone is curious. It might be used for a railgun as well.I never know how to pick out test gear. Maybe I should just get the cheapest I can find, and consider it disposable.

author: AG6QR
author_rank: Frequent Contributor
timestamp: October 14, 2013, 10:30:50 pm
content: Do you already have a voltmeter? There are several adapters that use hall effect current sensors (which work for both AC and DC) and put out a voltage proportional to the current they detect. You plug them into a voltmeter or oscilloscope to use them. That saves the cost of display.I own a Tecpel CA-60 clamp, which goes from 0 to 60 amps. The same maker builds a CA-600, to 600 amps. I've seen this same current clamp apparently rebadged by many makers. Prices vary widely, but some suppliers seem to be within your $50 budget. Search the web using terms like "CA-600 current clamp".My CA-60 seems to work well enough, though I don't have lots of precise equipment to compare it against. I've measured both DC and 60Hz AC currents with it and compared it to my Fluke 179 on the 10A range, and the measurements are comparable over the range where both methods could overlap. That's not a resounding endorsement for lab quality work, but for getting in the right ballpark on a demonstration, it's probably going to do the job.

author: TMM
author_rank: Frequent Contributor
timestamp: October 15, 2013, 09:12:35 am
content: The Uni-T UT204 (not to be confused with the 204A*) does AC TRMS and DC, is in your price range (~$55 shipped on ebay), reasonably accurate, however no power measurement capability and only up to 400A.*The 204A isn't True RMS, but is otherwise very similar and a few dollars cheaper.

author: ivan747
author_rank: Super Contributor
timestamp: October 15, 2013, 11:36:51 am
content: I just figured out having a true RMS clamp meter is more important than I thought. TRMS gives you the real AC measurement, as opposed to averaging multimeters. Traditional multimeters assume you are measuring a sine wave, but that is often not the case. You only get alternating current flowing like a sine wave when you attach a resistive load to an AC source, but if you use a different load like a switch-mode power supply or simply a traditional power supply you will get a current waveform that looks very different to a sine wave.In electric installations this should (in my opinion) happen more often than non-sinusoidal voltage. That's when TRMS in a clamp meter is important. In electronics you will get a mix of both non-sinusoidal voltage and current, specially in power electronics with all those TRIACs, PWM and such.

author: Rachie5272
author_rank: Regular Contributor
timestamp: October 16, 2013, 06:53:30 am
content: It looks like I'll go with the UT204 then. Thanks everyone.

author: Wytnucls
author_rank: Super Contributor
timestamp: October 16, 2013, 08:25:03 am
content: Quote from: Rachie5272 on October 16, 2013, 06:53:30 amHere my review of the 204 that might be of interest to you:https://www.eevblog.com/forum/testgear/uni-t-ut204-clamp-meter-review-and-tear-down/

author: Rachie5272
author_rank: Regular Contributor
timestamp: October 28, 2013, 10:36:29 pm
content: I got the meter, and so far it seems pretty decent. The last digit of the ammeter keeps fluctuating almost randomly, even when set on a table, but provides reasonable rough measurements, which is all I need.Unfortunately, I didn't properly estimate how much current my project is using: the meter maxes out on the 400 A range. Oh well.