CP-3 from B&K Precision for a DMM - Page 1
Forum section: electronics / testgear

author: PLS
author_rank: Newbie
timestamp: November 06, 2023, 04:12:31 am
content: In my work I need to be able to measure DC milliamps down to 100-200mA but all the way up to 20A. Finding a meter that can do this repeatedly, safely, and accurately is a challenge as I really don't want to carry two meters. I am currently lugging a Hioki DT4282 and Fluke 376 but want to ditch the 376 because I don't really trust it.My question is, could I use the CP-3 or a similar clamp with the Hioki (or any other DMM with a milliamp range)? Or does it require a certain type of meter? My plan is to use the clamp for the higher current measurements at work (and troubleshooting fleet vehicles issues when needed) and ditch the 376 altogether.

author: bdunham7
author_rank: Super Contributor
timestamp: November 06, 2023, 04:31:22 am
content: That clamp and many like it put out 1mV/A, so 20A would be 20mV--meaning you need a meter with a 200mV range if not lower--not a current range. Zeroing will always be an issue--note that the tolerances are 2% + 2A, quite a bit worse than your 376. Is your Fluke 376 broken or unreliable--or are you just having difficulty getting consistent readings with it?

author: Kleinstein
author_rank: Super Contributor
timestamp: November 06, 2023, 04:34:57 am
content: The CP-3 should work with any meter that can read mV. However it is relatively large (physically and with a 400 A range) and the accuracy specs are not very good. So one may not really be able to read 100 mA DC reliably.An alternative may be the UT210E clamp meter that also includes DC. chances are it is physically smaller and cheaper than just the CP-3 clamp. Having it all in one is less hassel than the extra wires connecting to a separate meter. There are quite a few reviews around for the UT210 versions. AFAIR the accuracy should be better, though still not great. Measuring DC with a clamp is a bit tricky, because it reacts the magnetic field. The smaller size can help for better resolution.

author: PLS
author_rank: Newbie
timestamp: November 06, 2023, 04:39:33 am
content: To clarify, I only use the 376 for the larger current measurements.My issue is that between the 376, 381, and 325, I will consistently read two to three different readings. While measuring inrush with the 376 and 381, I never get the same result on both. That's a super important thing for me and when they're 0.5A-1A apart it's difficult to trust them. Unfortunately I don't know which is correct at the moment.

author: bdunham7
author_rank: Super Contributor
timestamp: November 06, 2023, 04:52:45 am
content: Quote from: PLS on November 06, 2023, 04:39:33 amWe'd need more details, but that mostly sounds like life with clamp meters. I don't think the accuracy is specified for the inrush measurement and depending on the device/circuit, the actual inrush may be very different from instance to instance. What current are you measuring that you get a 0.5-1A difference? Are you measuring inrush on an AC or DC circuit? That's a 1000A clamp meter with a 0.5A accuracy floor, so it may not be the best device for your use--but unless it is broken it will be better than your proposed replacement.

author: PLS
author_rank: Newbie
timestamp: November 06, 2023, 08:46:56 am
content: Quote from: bdunham7 on November 06, 2023, 04:52:45 amI’m measuring a 24VDC circuit. It’s a large solenoid that draws 16A for a little less than half a second and then drops to roughly 1A.I’m not opposed to acquiring the appropriate meter so I’ll look around for an alternative. I wasn’t savvy on spec sheets when I bought it. Only learned recently when I noticed the inconsistencies that I’m not too happy with its performance in my situation.