Fluke 21 series 2 multimeter cat rating - Page 1
Forum section: electronics / testgear

author: 11mrjones
author_rank: Contributor
timestamp: September 26, 2025, 06:04:50 pm
content: Help with a quick question: my old fluke 21 series 2 is what CAT rating? I'm guessing I should label it as 1000V CAT II. On the front of the meter it doesn't label that CAT rating. In the manual it states under safety, class 2. It gives specs for 100V operation and also mentions that for current measurement to stay under 600V.So I'm guessing I could put a label on it as "1000V CAT II"..?See attached showing front of meter (there is now safety rating given on the back) and sections of manual.ThanksVictor

author: Someone
author_rank: Super Contributor
timestamp: September 26, 2025, 10:56:09 pm
content: The older standard is not compatible/equivalent so your proposed markings would be misleading.

author: Kean
author_rank: Unknown
timestamp: September 27, 2025, 11:41:42 am
content: Applying your own measurement category rating is invalid. The design has to go through standardised impulse voltage testing.In any case, CAT II has apparently been discontinued as a rating for handheld multimeters.https://www.eevblog.com/forum/testgear/multimeter-cat-ii-rating-discontinuation/

author: 11mrjones
author_rank: Contributor
timestamp: September 27, 2025, 07:42:32 pm
content: I'm not trying to be in strict accordance with regulatory bodies here. I wanted to simply put some label on it to remind me where and where not to use it. I had been using it around the house for generic wiring repairs before I was even aware of cat ratings,. So probably it's an equivalent to cat I (if that's still even a valid class as per the link given) and suitable only for electronics type repair, and probably should not be used on mains wiring. Perhaps I should just put a cat I on it, or not label it all?My 2 other meters are both agilent u1252a labeled as " cat iv 600v cat iii 1000v."Probably from now on I should use those for electrical wiring measurements or anything electronic or electrical which involves mains.And the fluke, where could one use it, up to 1000V but only for low energy circuits I guess?

author: J-R
author_rank: Super Contributor
timestamp: September 28, 2025, 12:28:16 am
content: I don't see any reason for concern with using this DMM in a residential setting, even with the missing rubber case. All of the inputs are overload protected to 500V, the jacks are well recessed, and both current inputs are fused.As is the case with any DMM, make sure the fuses are the correct ones, and inspect the test leads to make sure they are in good condition and are of the safety banana plug type.In my opinion, basic safety equipment is more critical than the DMM. Some thoughts:- Wear eye protection especially when working on live circuits, but honestly it's a good idea for the bench at other times. Exploding components, solder or other splatter, etc.- Wear long sleeves/pants, rubber soled shoes and gloves particularly when working in a live breaker panel. You can go crazy with thick gloves, but practically even just some thin oil-change gloves or similar will increase your safety factor greatly.- Only use one hand at a time, such as when making/breaking connections.

author: 11mrjones
author_rank: Contributor
timestamp: September 28, 2025, 04:05:13 pm
content: Fuse is as per fluke manual/part number and test leads are shrouded and in good shape. Thanks allV