Multimeter voltage ratings - Page 1
Forum section: electronics / testgear

author: diawollo
author_rank: Newbie
timestamp: August 23, 2016, 08:12:28 am
content: Hello, I'm little confused about multimeters ratings. Often they claim 600V VAC RMS/DC. Shouldn't it could be rated for 1.4 x 600VAC RMS for DC voltage? Or it's because of short peak duration on AC voltage?

author: Blastcap
author_rank: Regular Contributor
timestamp: August 23, 2016, 09:56:31 am
content: My guess, is that if something fails in a DC application it can continue arcing, opposed to AC that goes thru zero and will extinguish itself (unless the voltage/current is too high).

author: alanb
author_rank: Frequent Contributor
timestamp: August 23, 2016, 11:33:36 am
content: My guess would be that if the difference is significant you are not leaving a sufficient safety margin. If I needed to measure voltages in the 600v range I would want my meter to be rated for at least 1,000v and as such rms and peak would both be covered.

author: Neilm
author_rank: Super Contributor
timestamp: August 23, 2016, 06:48:23 pm
content: CAT ratings only apply for AC (mains). Some manufactures do put that sort of thing in their specifications, but technically it is wrong.Quote from: diawollo on August 23, 2016, 08:12:28 amNot necessarily. DC is there all the time, so creepage requirements go up significantly for DC versus AC at the same voltage (i.e. AC peak vs DC).

author: diawollo
author_rank: Newbie
timestamp: August 24, 2016, 01:20:11 pm
content: Both my multimeters is 600V RMS CAT III rated. I want to check PV system voltage 2-3kW power and up to 800V open circuit voltage. I've opened one multimeter and it has couple PTC's and MOV's. But all MOV's only rated to 510V strangelyIn what way they don't trip on 600Volts DC or AC RMS?It's UNI-T UT210e clamp meter.

author: Fungus
author_rank: Super Contributor
timestamp: August 24, 2016, 02:26:01 pm
content: Quote from: diawollo on August 24, 2016, 01:20:11 pmUni-T have been known to lie about their CAT ratings.I assume you want to measure voltage and current at the same time to get power.On balance: You'll probably be OK. The chance of a big spike from a solar panel is very small. The meter might die if something goes wrong but you'll probably live. Wear some work gloves for safety.(Important: Make sure the video camera is set up correctly for posterity...)

author: MosherIV
author_rank: Super Contributor
timestamp: August 24, 2016, 03:44:56 pm
content: QuoteWhat I have learned about MOVs is that they have 3 parameters :DC voltage rating (DC volts at which they will start to conduct)AC voltage rating (AC volts at which they will start to conduct)Clamp voltage rating (voltage AC or DC at which the MOV becomes a short circuit).I am not sure which one they print on the device case but it does not look good.

author: Lightages
author_rank: Unknown
timestamp: August 24, 2016, 03:48:26 pm
content: That voltages and currents on that solar panel array is enough to kill you instantly, before you can react. Don't play guessing games with Uni-T products not rated to handle those voltages. When dealing with these kinds of things you need to think about what you need and should do to protect yourself and not what might work. Use a multimeter rated for the voltages expected to be measured, ie 1000V, and follow proper high voltage procedures. Where rubber gloves, use one hand to connect things and keep one hand behind your back. Don't follow any advice to "give a try and let us know".For this kind of thing, get a Fluke, Brymen, Keysight, Gossen, Amprobe, Hioki, Sanwa, Yokogawa or other trusted brands with the proper ratings. Your life is worth the $150.