Low Current DC Clamp Meter - Page 1
Forum section: electronics / testgear

author: Mike Warren
author_rank: Unknown
timestamp: July 03, 2015, 10:31:17 pm
content: More and more often we are needing to measure the standby battery current in cars with everything shut down.This used to be a rare occurrence, so the inconvenience of disconnecting the battery wasn't an issue, but with the increasing use of electronic accessories in cars now days we have to do it more often. This is complicated on modern cars as many of them will draw well over an amp when the battery is first connected, which means the person doing it needs to make sure the meter is shorted out for a few seconds on initial connection. Mistakes are made and multimeter fuses get blown.I thought I'd see if anyone knew of a cheapish clamp meter that will measure DC current with at least 10mA resolution (preferably 1mA) and will fit over a car battery cable, which might be up to 13mm or so. Accuracy is not particularly important. It would take the job from minutes down to seconds.I haven't used a clamp meter for many years, and that was only on reasonably high current AC.

author: retiredcaps
author_rank: Super Contributor
timestamp: July 04, 2015, 01:29:52 am
content: No idea if this is any good or meets the car requirements, but saw this thread earlier when it got bumped.https://www.eevblog.com/forum/testgear/a-look-at-the-uni-t-ut210e/

author: Stray Electron
author_rank: Super Contributor
timestamp: July 04, 2015, 02:01:00 am
content: I frequently troubleshoot automotive wiring by looking at and tracing the current flow. It's a MUCH better way of troubleshooting some problems, such as mysteriously draining batteries, than by trying to look at voltages. What I do is to find a junction that I can break AND that I can also that I can connect amp meter probes to something on each side of. I connect the amp meter probes BEFORE I break the connection and then break the circuit. That way I never lose power to the automobile's circuits. After I'm done checking, I reconnect the junction, then remove the amp meter and I don't have to reset the alarm, the clock, the radio code, stations, etc etc.One place that I can usually break a junction is at the battery. I can't reliably connect to most battery posts so that's out but frequently the wires connecting to the various major devices areboltedto the battery clamp so I can connect one side of my amp meter to the battery clamp and the other to the wire. After the meter is set and connected, just unbolt that one wire and start reading.If there's no place to connect the amp meter to on the battery side I have resorted to having a helper push a probe against the top of the battery post and holding it there while I unbolt the clamp and slide it off of the post (thus breaking the circuit). I then have the helper hold the clamp above the battery post and with the insulated probe sticking through the clamp. As long as they can hold everything in place, you're go to go! Obviously this is only good for checks that you can make quickly. But if you need more time they can just slide the clamp back on the battery post and take a break while you figure out what to do next.PS: To avoid the possibility of shorting the battery, it's better to connect the amp meter in the return (aka ground) circuit instead of the "hot" side whenever possible. That way if you accidentally short something to ground there'slittleif any voltage difference and no current flow.

author: PTR_1275
author_rank: Frequent Contributor
timestamp: July 04, 2015, 02:06:55 am
content: Hi Mike,I know Altronics do one. I've had my eye on it for a while for the same reason. Never tried it so can't say the quality / accuracy but their gear is normally pretty good. The jaw might be a bit on the small side for big cables.http://www.altronics.com.au/p/q0968-compact-acdc-clamp-meter/

author: Mike Warren
author_rank: Unknown
timestamp: July 04, 2015, 02:37:29 am
content: Thanks for the replies.That Altronics one looks perfect, especially since we have a wholesale account with them and order regularly. I did look at it briefly, but missed the 4A range. Not sure how, since it's clearly written twice.I'll order one on Monday.

author: PTR_1275
author_rank: Frequent Contributor
timestamp: July 04, 2015, 02:44:07 am
content: Brilliant. Let me know how it goes and I might be persuaded to buy one as well.

author: Lightages
author_rank: Unknown
timestamp: July 04, 2015, 03:24:51 am
content: I believe that this is the original brand, just re-branded to for other companies.http://www.ebay.com/itm/DT337-AC-DC-Measurement-Mini-Digital-Clamp-Meter-Tester-Multimeter-for-CEM-/171741076657?pt=LH_DefaultDomain_0&hash=item27fc90dcb1

author: mtdoc
author_rank: Super Contributor
timestamp: July 04, 2015, 04:34:38 am
content: I bought one ofTHESEGTC branded meters a few years ago and am very happy with it. Martin Lorton did a review some time ago ( see below) As I recall it has decent accuracy in the millivolt range. I can't recall the exact specs but I did check it when I first got it and it was within those.It may be a rebrand of the cheaper ones above though it looks somewhat different. For one thing it's a right handed meter....

author: Someone
author_rank: Super Contributor
timestamp: July 04, 2015, 08:16:05 am
content: Clamps tend to wander around with their offset quite a bit, and can be a bit trying to use around the low end of their rating. Is a clamp a 100% requirement? You mention blowing fuses on meters, where a Fluke 87 has 1mA resolution to 6A and 10mA resolution up to the full 10A with a 20A surge rating. The high resolution and min/max/average modes are great for working on power systems.

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: July 04, 2015, 08:21:28 am
content: Frankie sold me one similar to those.Seems ok, but doesn't like the 1.2 volt NiMh rechargeable batteries.

author: BravoV
author_rank: Super Contributor
timestamp: July 04, 2015, 08:26:32 am
content: Quote from: Someone on July 04, 2015, 08:16:05 amAgreed, especially for clamp type measurement, a stable reading for DC low current within mA resolution is tricky.I own Agilent U1213A clamp meter, the specification for DC current at 40 Amp range is with resolution of 10 mA, but the reality that its useable resolution only at 100 mA.As the earth magnet it self can affect the sensor, cause just by waving the meter at the air at different orientation, the offset can jump within +/- 20 to 50 mA.Turning or waving the clamp orientation at nearby huge metal object like big metal drawer or machinery can affect DC amp reading even worst.

author: nctnico
author_rank: Super Contributor
timestamp: July 04, 2015, 09:06:13 am
content: When tracing low currents in a car it is better to disconnect the batter (the minus) and put a multimeter in series. Just don't turn over the starter or turn on the lights.

author: 0xdeadbeef
author_rank: Super Contributor
timestamp: July 04, 2015, 09:06:41 am
content: The Metrawatt Gossen meters (at least the X-TRA) can measure from 100µa to 10A (16A for short duration) via a single connector jack and a single fuse.https://www.gossenmetrawatt.com/english/produkte/metrahitx-tra.htmNote very cheap though. Offcial price (including VAT) is close to 600€.

author: HighVoltage
author_rank: Super Contributor
timestamp: July 04, 2015, 11:44:50 am
content: Quote from: PTR_1275 on July 04, 2015, 02:06:55 amThat indeed is a very good looking clamp meter with 1mA resolution.Is this Altronics brand specific to Australia?It seems they are not offering international sales.Where would one buy one of these in Europe?

author: Mike Warren
author_rank: Unknown
timestamp: July 04, 2015, 12:18:34 pm
content: Quote from: Someone on July 04, 2015, 08:16:05 amThe important thing is for the unskilled people using this to quickly get a feel for if the vehicle is drawing more than about 50mA or so. At the moment they are so scared of blowing up meters that they call me from my work to do the test for them. And it's getting more regular.Since this meter is so cheap, it's worth giving it a go.I did think about making a device with a small shunt and a couple of solid alligator clips that could be clamped between the battery negative terminal and its cable and then they could just use a meter on mV, but the speed of a clamp has a lot going for it. If the meter fails, I'll build the adaptor.

author: Mike Warren
author_rank: Unknown
timestamp: July 04, 2015, 12:20:38 pm
content: Quote from: 0xdeadbeef on July 04, 2015, 09:06:41 amI shudder to think of how that would be treated in our installation bays.

author: Mike Warren
author_rank: Unknown
timestamp: July 04, 2015, 12:27:14 pm
content: Quote from: HighVoltage on July 04, 2015, 11:44:50 amYes, but they just re-brand Chinese stuff.QuoteLightages posted a link to what looks like the same meter on ebay:http://www.ebay.com/itm/DT337-AC-DC-Measurement-Mini-Digital-Clamp-Meter-Tester-Multimeter-for-CEM-/171741076657?pt=LH_DefaultDomain_0&hash=item27fc90dcb1

author: 0xdeadbeef
author_rank: Super Contributor
timestamp: July 04, 2015, 12:28:10 pm
content: Quote from: HighVoltage on July 04, 2015, 11:44:50 amAs noted above, this is most probably a rebadge of some Chinese meter.Despite of the different buttons and the flipped design (if this isn't just the image), I would assume this Voltcraft rebadge is exactly the same thing.http://www.voelkner.de/products/501606/VOLTCRAFT-Stromzange-Hand-Multimeter-digital-VC-539-CAT-III-600-V-Anzeige-Counts-4000.htmlMaybe an alternative for Europeans:http://www.voelkner.de/products/210/Benning-Stromzange-cm-2-AC-DC.html

author: HighVoltage
author_rank: Super Contributor
timestamp: July 04, 2015, 12:52:43 pm
content: Very interesting.I found the re-branded Voltcraft VC-539 about 10 km away from me in a Conrad store.Thanks for all your suggestions, I will get the probe next week and test it out in the mA range.

author: Rupunzell
author_rank: Frequent Contributor
timestamp: July 04, 2015, 02:55:55 pm
content: The classic clamp on DC current meter was the hewlett packard 428 (1958) the 428B (1961). It is a flux gate magnetometer based current meter. The 428B version had a full scale range of 1mA to 10A. Range sensitivity can be increased by adding a loop or loops of the wire carrying the current to be measured around the current probe aperture. Or splitting the current by using one or more wires to carry the current to be measured.Notable in the hp 428B, at the 3mA and 1mA full scale current range, there is an adjustment to compensate for the earth's magnetic field. If this compensation is not done, measured current accuracy is affected.There is a large aperture probe for higher currents and a magnetometer probe for measurement of magnetic fields.http://www.hpl.hp.com/hpjournal/pdfs/IssuePDFs/1961-11.pdfYes, is fire bottle based and work really well in good condition. Fire bottles are not a reliability or service life liability.When hp discontinued the 428B after decades of production, Applied Physics purchased the design and produces two version of this clip on current meter to this day, 428C and 428D along with a portable version 428P. These Applied Physics current meters are fully compatible with the all hp current probes made for the 428.http://appliedphysics.com/products/products/Bernice

author: 0xdeadbeef
author_rank: Super Contributor
timestamp: July 04, 2015, 06:32:12 pm
content: For the sake of completeness, for ~300€ (incl. VAT) Benning offers the CM 11 which has a 300mA DC range with a 0.1mA resolution (±1%+10 Digit)http://www.benning-shop24.de/stromzangen-benning-cm-11-044067-p-784.htmlBTW: why prefer the VC-539 over the Uni-T UT210E? Well, Uni-T doesn't have the best reputation, but at least the manufacturer is clear. Besides, the input protection looks better, it's True-RMS, has better (claimed) accuracy in the lowest DC ampere range (±2%+3 digits vs. ±4%+10 digits) and costs half of the VC-539...

author: korlatos
author_rank: Regular Contributor
timestamp: July 05, 2015, 02:45:25 am
content: AEMC K100 provides 1mV/mA output signal and can measure from 100uA to 4.5A DC.http://www.testequipmentdepot.com/AEMC/accessories/current-measurement-probes/ac-dc-microprobes/k100.htm

author: korlatos
author_rank: Regular Contributor
timestamp: July 05, 2015, 02:58:55 am
content: Quote from: korlatos on July 05, 2015, 02:45:25 amBTW, K100 uses flux gate magnetometer technology, just like HP 428B.http://www.aemc.com/products/html/view.asp?id=204&dbname=products

author: nowlan
author_rank: Frequent Contributor
timestamp: July 05, 2015, 04:26:55 am
content: Review: CEM DT-337 milliamp clamp meterhttp://www.cem-instruments.com/en/pro/pro-519.html

author: 0xdeadbeef
author_rank: Super Contributor
timestamp: July 05, 2015, 06:49:02 am
content: I stumbled over another mA clamp meter made by company called Prova from Taiwanhttp://www.wisoft.com.tw/prova/jsp/provafront/prova.jsp?lang=en#The Prova 11 (TrueRMS) claims ±1.5% +5dgts in the DC mA range (0-4A).Pretty expensive though (230€-300€) for an unknown brand and a little hard to come by.There's also a probe version of this called Prova 15.The Prova 11 is obviously also rebranded asExtech 380942

author: mcinque
author_rank: Unknown
timestamp: July 05, 2015, 08:40:24 am
content: I suggest PICO TA018, it's relatively cheap (€ 150) and has a good sensitivity and a better rejection noise than its previous version. I acquired it recently, and I'm very satisfied.100mV/A on 20A range, so 10mV/100mA with 10mA minimum sensitivity (but it's readable even with 5mA), should fit your needs10mV/A on 60A rangehttp://www.picoauto.com/current-clamp-small.html

author: 0xdeadbeef
author_rank: Super Contributor
timestamp: July 05, 2015, 10:21:45 am
content: Quote from: mcinque on July 05, 2015, 08:40:24 amLooks like a rebrandedCA-60which is sold under different brand names.Also theHantek CC-65seems to be a very close relative.

author: mcinque
author_rank: Unknown
timestamp: July 05, 2015, 02:17:03 pm
content: Probably, until your post I was convinced that Pico doesn't do rebrandingIs this a known behavior of Pico? Or who's rebranding who? (Or who's copying who?)EDIT: Found that TECPEL seems to offer his UNI-T UT81 (http://www.tecpel.com/Oscilloscope-multimeter-OS-81B.html) or it's UNI-T that rebrands TECPEL?Also Tenma offers a rebranded UT81, don't kow if TECPEL or UNI-T.The rebranding is a very disappointing thing.

author: 0xdeadbeef
author_rank: Super Contributor
timestamp: July 05, 2015, 02:36:34 pm
content: Yeah, it's all a big mess. I also noticed that thisTecpel DCM-043looks exactly like the "GTC CM100" mentioned earlier in this thread.I sometimes wonder if at least all these Chinese and Taiwanese companies know who copies from whom. But honestly I tend to think they lost the overview as well.

author: Rupunzell
author_rank: Frequent Contributor
timestamp: July 05, 2015, 03:55:06 pm
content: K100 & K110 might use a flux gate as a measurement device. Both have a percent of reading and + or - 150 to 200 uA ( 1mA/mV or 1mA/10mV) added tot he reading making both not very accurate at the 1mA range. With that much error, both would be more of an indicator of current than accurate measurement.Measurement error is further increased by the accuracy of the instrument used to make mV measurements. Accurate measurement of millivolts is no easy task for any volt meter. Then there is stability and drift to deal with.K100http://www.aemc.com/products/pdf/1200.67.pdfK110http://www.aemc.com/products/pdf/2111.73.pdfBeyond this, noted at the bottom of their spec sheet is absence of magnetic fields. This likely means the flux gate sensor is not well shielded and subject to stray field pick up and there appears to be no compensation for the Earth's magnetic field.Sensing device type alone does not give an inherent measurement advantage unless the design, implementation, construction has the required details to make it a truly useful instrument.BerniceQuote from: korlatos on July 05, 2015, 02:58:55 amBTW, K100 uses flux gate magnetometer technology, just like HP 428B.http://www.aemc.com/products/html/view.asp?id=204&dbname=products

author: Mike Warren
author_rank: Unknown
timestamp: July 08, 2015, 03:52:21 am
content: The Altronics meter arrived today. It's definitely identical to the CEM DT-337 that MJLorton reviewed.I'm not impressed with it; build quality and UI quirks, but I think it will do what I want.Looking inside, it seems they forgot that CAT III 600V meters are supposed to have some sort of input protection.

author: PTR_1275
author_rank: Frequent Contributor
timestamp: July 08, 2015, 04:07:27 am
content: That's a shame.I don't think I've ever used my clamp meters for voltage readings before. I just checked my der ee and finest clamps and both are rated cat 2 600v. I wouldn't trust the der ee at 600v but I've not looked inside at input protection.How does it go with current accuracy / resolution?

author: Mike Warren
author_rank: Unknown
timestamp: July 08, 2015, 04:19:39 am
content: Quote from: PTR_1275 on July 08, 2015, 04:07:27 amI won't be using this one for anything other than DC current, so it doesn't matter to me. I just opened it up because I thought some people here might be interested.QuoteMuch like the results Martin gets. It's finicky to get right. The zero button is a latch. That just doesn't make sense. You have to tun it off and back on before each reading.As well as testing it on the bench, I tried it on 9 cars we have here. A couple of them have battery cables that are too thick for the clamp. I found the best accuracy was obtained by holding the meter right next to the cable I wanted to measure, zeroing the meter, and then clamping it on, keeping the angle the same as it was while zeroing it.

author: retiredcaps
author_rank: Super Contributor
timestamp: July 08, 2015, 05:51:31 am
content: Quote from: Mike Warren on July 08, 2015, 03:52:21 amThanks for sharing pics of the insides. Martin never showed the insides in his video.The green component by the flat flex connector might be a MOV (varistor)? That yellow component is a PTC and labelled as such.