Is CAT II a useful rating for a multimeter? - Page 1
Forum section: electronics / testgear

author: Fungus
author_rank: Super Contributor
timestamp: April 26, 2023, 08:41:54 am
content: The is a branch from another topic where I was wondering if "CAT II" is a useful safety marking.The standard says that:CAT III:Appliance outlets with short connections to service entranceCAT II:Outlets at more than 10 meters (30 feet) from CAT III source.Outlets at more than 20 meters (60 feet) from CAT IV source.( ref:https://www.fluke.com/en/learn/blog/safety/multimeter-guide)So, given that:a) There's basically no difference in price between a CAT II multimeter and a CAT III multimeter.b) You can't tell what rating a mains socket is just by looking at it so you have to assume it's CAT III.What use is CAT II when you're looking to buy a multimeter? Shouldn't you just go for CAT III and be done with it?To me CAT II marking just seems to say "Don't buy me, get a CAT III meter instead!"nb. I'm not arguing that there shouldn't be a difference between CAT II and CAT III safety precautions and procedures, eg. use of PPE in CAT III environments. Maybethatshould be separated out from the markings on test gear.

author: Fungus
author_rank: Super Contributor
timestamp: April 26, 2023, 08:45:50 am
content: The other thing that came up in that discussion is that CAT I seems to have been deprecated and removed from the IEC standards.To me CAT I seems like a useful rating, it says "I'm only safe for low energy measurements".If I was in charge of removing one of the ratings from multimeters I'd have removed CAT II, not CAT I.I'd have renamed then, too, to avoid confusion. As noted above I'd be fully behind a movement to separate the markings on meters from safety procedures when using them.

author: Someone
author_rank: Super Contributor
timestamp: April 26, 2023, 11:03:53 am
content: Fluke isn't following the standard from which those categories are defined (61010) and would be misleading intypicalinstalls in Australia and the UK (and probably other countries that I am less familiar with).61010 measurement categories are really simple:"CAT III is for measurements performed in the building installation""CAT II is for measurements performed on circuits directly connected to the  voltage installation"As mentioned in the other thread(s), its very very simple: something that plugs into a socket outlet is immediately CAT II, unless you are on the other side of safety isolation/insulation and then its up to you to know what the range of voltages/currents could be (perhaps use a more modern standard to help) and check that the multimeter/measurement tool has suitable withstand and/or breaking capacity.

author: EEVblog
author_rank: Unknown
timestamp: April 26, 2023, 11:18:49 am
content: Easiest to just keep this basic rule, if you work on anything to do with the mains, either plugin or fixed mains wiring, have a certified CAT III rated meter as a minimum.If you are an industrial or plant electrician you'd want a CAT IV. I'd personally use a 1000V CAT IV meter in that scenario (Fluke don't even offer one of those AFAIK)The biggest risk though is a meter that physically has a current range and accidently using it on a mains connection.A huge surge on a mains line that blows up your CAT III/IV meter in voltage mode in most common scenarios is so rare it borders on negligable risk.

author: EEVblog
author_rank: Unknown
timestamp: April 26, 2023, 11:22:31 am
content: That brings up a the question, what is the safest/bested meter on the market?Check out this bad boy, and that connector spacinghttps://www.hdt-electronic.com/en/products/digital-multimeter-series-200xx/digital-multimeter-autorange-and-trms-1000v-cat-iv-1000v/

author: Gyro
author_rank: Super Contributor
timestamp: April 26, 2023, 11:33:36 am
content: It's a shame they put the uA range on the voltage input jack.

author: Fungus
author_rank: Super Contributor
timestamp: April 26, 2023, 11:40:52 am
content: Quote from: EEVblog on April 26, 2023, 11:22:31 amBut does it have this fuse?(with shield installed)https://www.eevblog.com/forum/testgear/any-experience-with-an-amprobe-hd160c/

author: Fungus
author_rank: Super Contributor
timestamp: April 26, 2023, 11:46:45 am
content: Quote from: Gyro on April 26, 2023, 11:33:36 amIt doesn't have amps so maybe it's only "uA" for flame sensor testing, like theFluke 116.ie. No fuse and chunky internal protection on that range.

author: Fungus
author_rank: Super Contributor
timestamp: April 26, 2023, 11:56:01 am
content: Quote from: EEVblog on April 26, 2023, 11:22:31 amIf I had to choose a Fluke for poking around industrial things I'd probably go for theFluke 113.CAT IV 600V, only two input jacks, only two dial positions, mostly automatic function selection.Fluke doesn't do CAT IV 1000V so that's their top CAT rating combined with their lowest possibility of operator error.Why would I pick a Fluke when other brands do higher CAT ratings? Yellow meters get you past the guards at the gate and make the site foreman leave you alone to get on with the job - that's another safety feature.

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: April 26, 2023, 12:10:58 pm
content: Quote from: Fungus on April 26, 2023, 11:56:01 amFluke T5-1000 I recommend though I don't like the detachable probes.For bullet proof, I rocked the Fluke T2 for many years. No switches or buttons. Mine died finally. They did have some recall issues, so don't know how good it's blast protection was/is.

author: EEVblog
author_rank: Unknown
timestamp: April 26, 2023, 12:28:55 pm
content: Quote from: Fungus on April 26, 2023, 11:46:45 amYep, no fuse needed. Well, they probably use a chunky fusible resistor followed by big MOVs.

author: EEVblog
author_rank: Unknown
timestamp: April 26, 2023, 12:30:08 pm
content: Quote from: Fungus on April 26, 2023, 11:56:01 amYeah, if I was an electrician that's what I'd carry.

author: xrunner
author_rank: Super Contributor
timestamp: April 26, 2023, 12:41:02 pm
content: Quote from: Fungus on April 26, 2023, 08:41:54 amI'm brushing up on this stuff myself, hadn't thought about it for a while. As I understand it, between CAT II and Cat III, after the breaker, there is nothing but wiring (am I wrong?). Yet you could have some outlet strips (extending the CAT II scenario from the outlet by a few feet) with surge protection so it's not that simple from another point of view. Maybe it is simpler to just use CAT III for everything up to the device power input connection.

author: EEVblog
author_rank: Unknown
timestamp: April 26, 2023, 12:55:07 pm
content: Uni-T make a 1700V meter, but it's only CAT IV 600Vhttps://meters.uni-trend.com/product/ut196/and the UT892 for 2000Vhttps://meters.uni-trend.com/product/ut892/Inside:https://www.eevblog.com/forum/testgear/new-uni-t-ut892-2000v-acdc-high-voltage-multimeter/msg4404907/#msg4404907

author: madires
author_rank: Super Contributor
timestamp: April 26, 2023, 12:58:10 pm
content: Alternative: Benning has some nice DMMs for sparkies and industrial applications. IIRC, my Duspol (not a DMM) is CAT IV 1000V.

author: EEVblog
author_rank: Unknown
timestamp: April 26, 2023, 01:11:54 pm
content: APPA S3 2kV:https://www.avo.co.nz/products/low-voltage-and-contractor-tools/digital-multimeters/1439-appa-s3

author: madires
author_rank: Super Contributor
timestamp: April 26, 2023, 01:23:05 pm
content: 1500 V AC/2000 V DC: BENNING MM 10-PV (https://www.benning.de/products-en/testing-measuring-and-safety-equipment/digital-multimeter/pv-multimeter-mm-10-pv.html). Looks very similar to the APPA S3 2kV.

author: joeqsmith
author_rank: Super Contributor
timestamp: April 26, 2023, 01:27:22 pm
content: Quote from: Fungus on April 26, 2023, 08:41:54 amFault currents change which I would assume drive up the cost of safety fuses and other materials. I wouldn't be surprised that the costs for certification are not higher as well. I'm sure the ignorant will chime in with how testing should not cost much and fuses are free.

author: Neilm
author_rank: Super Contributor
timestamp: April 26, 2023, 06:29:00 pm
content: IEC61010-2-33 is the part for multimeters. it states that meters must be rated for 300 V CAT III at a minimum.

author: switchabl
author_rank: Frequent Contributor
timestamp: April 26, 2023, 07:30:51 pm
content: Well, Part 2-033 applies to "hand held meters that have a primary purpose of measuring voltage on a live mains circuit". That is more or less CAT III (or IV) by definition. A lower-rated one (or a bench multimeter) would just fall under Part 2-030 instead.An example is the Uni-T UT131 series:https://www.triopak.fi/files/product/UNI-T/UT131%20Series%20CE-LVD.pdfBut electricians won't buy something like this and they probably make up most of the (serious) multimeter market. So it doesn't make much sense as a product unless it is very low-cost. Or a specialized meter for the electronics market (most bench meters are CAT II).