Tacklife CM01A and CM02A clamp dmm opinions please. - Page 1
Forum section: electronics / testgear

author: shteii01
author_rank: Frequent Contributor
timestamp: March 03, 2019, 02:30:16 am
content: Anyone has one?Any teardown pics?Are they toys or can I actually put them on 460VAC 3 phase motor and they will survive?(Is the CAT rating real or just a pretty picture?)Interestingly, 01 clamp will do dc and ac current, but the continuity is not a separate function. On the other hand, 02 has low z and separate continuity function, but clamp only does ac current.cm01a:https://www.amazon.com/Multimeter-Auto-Ranging-Continuity-Electrical-Capacitance/dp/B01N014USE?th=1cm02a:https://www.amazon.com/Multimeter-Auto-Ranging-Continuity-Electrical-Capacitance/dp/B071CLZF4J?th=1

author: totalnoob
author_rank: Regular Contributor
timestamp: March 03, 2019, 01:21:04 pm
content: I would put good money on the CAT rating being pretty much bogus on these. Obviously, you are asking to use these in a commercial/industrial environment and pretty much noone here would recommend one of these for such use. Personally, I think you'd be OK with using the clamp part since there should be no contact between anything inside the meter and the actual circuit, but I would not use the other features on anything but <50V electronics and even that I would not use in a commercial/industrial setting since there is a risk you may accidentally test the higher energy side, if you run into a poorly marked controls cabinet (like for an air handling unit or other equipment). Anyway, I believe you are probably looking to only carry one meter, but if you were to buy this meter, you would need a two meter solution, the clamp on meter I believe will be OK for taking amp readings but for any other multimeter work, you'll need a good and safe multimeter.Pretty much the general consensus here is the Brymen meters are the best bang for the buck, as their CAT ratings are not bogus and they are as robust as the Fluke's, for less money. I didn't check to see where you're from, the problem with Brymen is that they are pretty hard to find in the US. They are sold under the Greenlee brand here and have a significant markup. The EEVBlog branded Brymen would probably be a very good meter for what you need and I believe it is sold in the US on Amazon. There's also a Polish site (TME.com.eu?) that you can buy a Brymen for a reasonable price and have it shipped, not sure if the tariffs now changed the price difference between buying a Greenlee vs. importing from Poland, but you can look into it. Now, Brymen DOES make clamp meters which may also meet their CAT ratings, I am not sure if there are any reviews, but perusing Brymen's website and looking through their materials may point you to a clamp DMM that you could also safely use the other functions on, not just the clamp.

author: gby
author_rank: Frequent Contributor
timestamp: March 04, 2019, 12:52:48 am
content: I saw the Tacklife CM01A on Amazon for only $14.38 delivered and bought one to get a clamp meter DC and AC up to 400 A. It seems to be pretty good but it does have two problems:- The Amazon listing said it was TRMS. If definitely isn't TRMS. 1 Vrms 100 Hz sine wave reads correctly while 1 Vrms square wave reads 1.11 Vrms which is what you would expect if the meter just rectified the input and took a dc reading scaled to read correctly for sine waves.- The color scheme of white lettering on orange background on the black plastic case is a bit hard to read in marginal light.For measuring line frequency motor currents I think you would be OK. I agree that we should be suspect of the CAT safety rating when using leads. But, for using the clamp meter to measure current even for 480 Vac lines I would feel safe with this meter. Not so much for putting high voltage on the meter in Ohm mode for example.For my day job I design servo drives for Kollmorgen and when I tried to measure motor current on a 480 Vac PWM inverter driven motor I did not get a good reading with this meter. I bench tested the meter frequency response and it was -3 dB at 7 kHz so it should have been OK rejecting the 11 kHz PWM of this drive. Ideally it would have worked but I will admit I did not put a lot of effort into figuring our what was going on. Maybe the motor speed was too low and the amp clamp doesn't like 20 Hz and less in ac measurement mode.For the price I paid I am happy with it but I would not recommend it as a lab grade instrument.

author: totalnoob
author_rank: Regular Contributor
timestamp: March 04, 2019, 12:42:17 pm
content: Good point about the issue with trying to read motor current when its driven through a VFD. Our Electric Shop had to lend a true RMS clamp meter to an HVAC testing and balancing technician because the technician could not get an accurate current reading from his clampmeter when we were testing an exhaust fan that was just installed. The exhaust fan was driven through a VFD. Yet another reason to get a reputable clampmeter if you are going to use this in a commercial/industrial environment. If you have supply your own tools for work, I'd get a Brymen. Yes, its more expensive than other options and I know with tax law changes, you likely won't be able to write off such an expense as in the past, it's still better to get equipment that will give you an accurate reading and be safe.

author: shteii01
author_rank: Frequent Contributor
timestamp: March 04, 2019, 06:05:33 pm
content: As far as VFD driven motors (which is all I do really), I am not worried about current. We usually have 0.5-1 A running from VFD to motor.