Do we need True-RMS clamp meter ?  - Page 1
Forum section: electronics / general

author: Kiriakos-GR
author_rank: Super Contributor
timestamp: April 24, 2010, 02:33:25 am
content: Well I am doing some thoughts about getting an clamp meter.All that I care as specs , are 400 AC/DC 100A Max.If there was an accessory as an clamp, to be connected on a multimeter, this one would do also.I found many Fluke 30 and 32 on ebay as used, but I do not know how old are they,plus I do not know if the True-RMS has any effect in the measurements of Amperage.The truth are that I am not willing to spent much, that why I am looking for used ones.

author: Unknown
author_rank: Unknown
timestamp: April 24, 2010, 09:41:06 am
content: Do you need a clamp meter? Not sure, you'll have to determine that for yourself. I've always considered most clamp meters as designed for industrial use, I don't handle anything near 100A, and my conductors are a lot smaller than those clamps. You should state your intended applications.You probably do want true-RMS, unless you know that your current waveforms are perfectly sinusoidal. For anything with switchers, you need true-RMS. Do note that multiplying voltage and current will give you VA (apparent power), not W (real power). Any meter not explicitly marked true-RMS probably isn't true-RMS.Other useful features are the ability to measure DC and the bandwidth (determines how well it measures higher frequency components). Fluke probably has a useful white paper about clamp meters

author: Kiriakos-GR
author_rank: Super Contributor
timestamp: April 24, 2010, 12:16:52 pm
content: Well , my only main interest are to be able , to measure low-voltage( 220 or less) amperes AC/DC .And so I will eliminate the need to split wires.I have a pile , of ampere meters and DMM's ( as known )If for an such "average" need , the 10$ ones can do it , them I will just take one of those.I do not care about the DMM on the clamp , I need just one clamp that could do mostly measurements in amperes.

author: PetrosA
author_rank: Frequent Contributor
timestamp: April 24, 2010, 01:27:59 pm
content: Kiriakos, I would recommend that you get a clamp for your Fluke. Beware, there are clamps for AC only, and clamps for AC/DC, you will need the one that measures both. You should be able to find something on eBay, but do your research first. When I was thinking of getting that kind of setup, it was recommended to look at Fluke and AEMC (Chauvin-Arnaux) clamps. There are also clamp meters designed specifically for low amperage measurements. Pay particular attention to the specifications to get what you really need.

author: Kiriakos-GR
author_rank: Super Contributor
timestamp: April 24, 2010, 07:10:42 pm
content: Thanks for the tip ... found the AC one .. Documentation here..http://www.tequipment.net/pdf/80I400_InstructionSheet.pdfI will investigate more , its not an urgent task.Still if any one haves any links about clamps for DDM , please add them .

author: Kiriakos-GR
author_rank: Super Contributor
timestamp: April 24, 2010, 08:00:53 pm
content: Hmmm I was not aware that the DC part about clams , was such an issue that leads the prices to crazy levels...I will start to split wires again ..I have all ready spent allot this month.

author: PetrosA
author_rank: Frequent Contributor
timestamp: April 25, 2010, 02:54:57 am
content: http://www.tequipment.net/AEMCMR411.htmlUnfortunately, they aren't cheap, but neither is a decent clamp meter. Fluke would probably be more expensive yet...

author: Kiriakos-GR
author_rank: Super Contributor
timestamp: May 18, 2010, 04:02:52 pm
content: The truth are that I am puzzling for two weeks now , I did found one AEMC 411 in a sweet price,but ... but .. its not True RMS at AC , I had even to register my self in France ( web page )so to find out that its only 45-65 Hz .. or any way its does not say cleanly what it does.Check attached file ..And the thunder came again from China .. by looking this UNIT-T product, that has incredible specs,and tremendous low pricing.http://www.uni-trend.com/UT204.htmlIts not a probe, its one complete unit.It looks to have it all .The only thing that looks tricky , are the operating temperatures VS accuracy .It says something like 23C +/_ 5 Celsius .In comparison with the AEMC , it looks to be stable at max 50 Celsius.The UNIT-T AC/DC True RMS clamp looks to be a product of 2005 = New .All that I care most are the 0 - 40 or 60 A .. AC/DC True RMS

author: PetrosA
author_rank: Frequent Contributor
timestamp: May 18, 2010, 10:54:06 pm
content: Quote from: Kiriakos-GR on May 18, 2010, 04:02:52 pmThe R.H. after the temperature stands for relative humidity. If you can wait for an AEMC at a good price, I would recommend that instead of this meter. This meter doesn't seem to have very good safety specs, and by definition, you will use a clamp meter near mains, especially if you're looking to read up to 60A. I wouldn't worry too much about stability at 50 Celsius, since that is really an extreme temperature, even for Greece. If you leave a meter in your truck or car and it heats up from the sun, let it cool down before using it.

author: Kiriakos-GR
author_rank: Super Contributor
timestamp: May 18, 2010, 11:20:36 pm
content: @PetrosADo me a favor and check the attachment above ( PAC 12 .pdf ) to see by your self , if the AEMC are True RMS ..After the first pages , it has English ones.

author: PetrosA
author_rank: Frequent Contributor
timestamp: May 19, 2010, 11:37:52 am
content: Quote from: Kiriakos-GR on May 18, 2010, 11:20:36 pmTable 4 on page 10 indicates that AC measurements are RMS, so probably TRMS. Since it's a dedicated AMP meter, that would make sense.

author: Unknown
author_rank: Unknown
timestamp: May 19, 2010, 03:49:29 pm
content: RMS may also just mean Vp-p / (2*sqrt(2)), which is correct for pure sine waves. If the bandwidth is 45-65Hz, it's unlikely to be true RMS, since anything will be a sine with such a narrow bandwidth. And even if it is true RMS, the harmonics that distort your sine are likely to be outside that range. If it were trueRMS, I would expect them to proudly announce it, like Fluke does on (almost) every true RMS instrument.

author: Kiriakos-GR
author_rank: Super Contributor
timestamp: May 19, 2010, 09:00:51 pm
content: I do not know what to do ... The " Good " clamp was made at 2004 .Looks to be RMS by having in mind the center of 50Hz ..The UNIT-T has one model called as UT-203 , that the only deference with the UT-204 ,are that the 204 are True Rms .. just for that reason, they made a new clamp model !!What I need to do , are to be able to measure the Amperes in the output of UPS Battery Backup systems.The Input its AC Mains , any clamp can do that .The output when running on batteries , its the upcome of the internal inverter.No one can tell how good quality will be ( Clean output in Hz ) .Because of the UPS Battery Backup systems , I got the Fluke 87-5 , so to be able to measure the volts .Now I need one damn good clamp , so to be able to measure the Amperes too.If I did not had to deal with UPS Battery Backup systems , I would not bother to get the Fluke DMM at all.

author: PetrosA
author_rank: Frequent Contributor
timestamp: May 20, 2010, 03:16:10 am
content: Do you need to measure the load on the batteries (before the inverter) or the AC after the inverter? If you need to check the load on the batteries, any ACDC clamp will be accurate, since there wouldn't be any waveform distortion involved. I'm not sure what benefit you would have from measuring the load after the inverter, but you would definitely need a TRMS meter for that since IIRC, most UPS inverters don't output a sine wave when on battery.

author: Kiriakos-GR
author_rank: Super Contributor
timestamp: May 20, 2010, 03:38:20 pm
content: By the though that I will get something good , I like to be able to do it all .Even measuring the Load of the AC output.My expensive APC does have an basic output load indicator ( 5 LED's), the cheap ones does not have.Found an alternative solution, EXTECH MA120 , but its very hard to get it, in Europe.Even from ebay.

author: Kiriakos-GR
author_rank: Super Contributor
timestamp: May 20, 2010, 07:17:22 pm
content: I killed many hours even today at searching from US to Japan, and back and for worth , and I realize that even in the category of smart clamps ,the manufacturers baptize their products with what ever title they like ...Found as expensive True RMS AC clamps , some that does AC current measurement at just 50/60Hz ..and calculate the True RMS by software ..The made in France one, does 45/65HZ ( The best so far )Before few minutes found theTriplett 9320-ATrue RMS AC/DCAC 40/100Hz, First place so far ...Resolution 0.1A and very good accuracy .http://www.jewellinstruments.com/pdffolder/triplettpdfs/84-858.pdfThe AC bandwidth at Current measurement , are the most delicate spot in all .The one that it does this well , it does all the rest too.Still looking, but now at list I know how to compare them.And what to look in the specs .

author: PetrosA
author_rank: Frequent Contributor
timestamp: May 20, 2010, 11:00:09 pm
content: The price on this one is good:http://www.tequipment.net/ReedST-9800T.asp

author: Kiriakos-GR
author_rank: Super Contributor
timestamp: May 20, 2010, 11:44:14 pm
content: I did took a look , does not look special in specs .For the same Price I can get the Triplett 9320-A , that looks like an more refined product.Another issue that bothers me are the Dollar Euro Balance ..Any way I will wait, until to find the best ever solution.