What multimeter to use for motor control panel?  240v - Page 1
Forum section: electronics / testgear

author: Housedad
author_rank: Frequent Contributor
timestamp: March 01, 2017, 09:13:10 pm
content: I have a VFD motor control panel that I designed and built for my milling machine. 1.5HP 3 phase motor on the VFD and everything else runs off a 750VA transformer. I am about to do the initial testing of the unit and I assume that a catIII meter would be needed. What would you recommend as a safe meter to use? I have a BK precision 2709B in the mail, but I'm not quite sure it would be safe for that circuit. If I should get a more robust meter, I'd need to keep it south of $200. This meter will basically replace the two (really) old handheld meters I have and be used for everything that does not go on my test bench. The 2709b and two bench DMM's I havenwill never leave the bench.I have a blog about the design that I haven't updated in months as I had surgery and could not use my arms much but it shows the circuit and machine.http://www.thebionicuniverse.com/vfd-design-and-implementation/Thanks!

author: Jeroen_Bezemer
author_rank: Contributor
timestamp: March 01, 2017, 09:39:10 pm
content: Quote from: Housedad on March 01, 2017, 09:13:10 pm240V equipment should need at least 600V Cat3 meter for being safe. Do not go below that, and don't pick a cheap Chinese meter with ChinaExport logo.Verstuurd vanaf mijn SHIELD Tablet met Tapatalk

author: The Soulman
author_rank: Super Contributor
timestamp: March 01, 2017, 10:43:03 pm
content: That BK precision 2709B probably won't blowup when used appropriately and is true rms and can do frequencymeasurement, it even has a 600 Volt cat III rating.However a meter should inspire confidence and I'm not to sure if its doing that for me, for you it can obviously be different.I have a metrawatt metrahit 2+ (M205A), a fairly basic meter but its build quality is very high and even comes with acalibration report.It's available at amazone around the 250 us dollar mark, comparable to the fluke 175 but still much prefer the metrawatt.Personally I would't use a meter from a price point below that (with inevitable a lower build quality and/or from unknown brand)for that type of work.It's all about confidence.If you don't have any, invest in (cat III rated) grippers/clamps/magnets that makes taking measurements so much easierand most of all safer.Probably also wan't to buy a current clamp.

author: james_s
author_rank: Super Contributor
timestamp: March 01, 2017, 11:24:05 pm
content: You can't go wrong with a Fluke.I would probably just use the meter you already have. Do give it a checkout if you don't know the history. Make sure it has a fuse of the proper type and value installed, not bypassed with a wire or something. Check the test leads to make sure they're in good shape and of reasonable quality. Take care not to do the classic stupid move of trying to measure voltage while using the amp settings.

author: CustomEngineerer
author_rank: Frequent Contributor
timestamp: March 02, 2017, 01:55:58 am
content: For a little over $200 I would recommend the Brymen BM869S. Rated 1000V Cat IV and has a VFD measurement setting.http://www.tme.eu/en/details/bm869/portable-digital-multimeters/brymen/bm869s/

author: Paul Moir
author_rank: Frequent Contributor
timestamp: March 02, 2017, 07:56:33 am
content: Personally I don't see what the big deal is. This is at best a CAT III 300V situation you're talking about here, and the meter you have in the mail is rated for CAT III 600V. While its CAT II 1000V rating is suspicious in these modern times, you are not using it here. While not a Fluke nor a Gossem it's not some no-name brand either. And being on a machine tool you'll probably appreciate the magnetic holster.Personally I would go out and buy some handy quality reasonably CAT rated probes such as alligator clips or those big hook probes Fluke sells. With some helpful tools like that can make your life easier and lower the chances of electrocuting yourself, which I think is far more likely a problem than having your meter blow up on you.Note that lurking inside the VFD are voltages over 400V, but that should be no problem for that meter either.http://content.fluke.com/promotions/promo-dmm/0518-dmm-campaign/dmm/fluke_dmm-chfr/files/safetyguidelines.pdfEDIT: ... then it's apostrophe s. Scalliwag!