Products > Test Equipment
DMM safety
J-R:
I have the Amprobe-branded version of the BM089 and sent some reasonable voltages through the uA DC mode as a test. I think their rating limit of 1,000VDC/VAC is correct, but above that it may have to sacrifice a component or two. I didn't try it...
My opinion on these safety ratings is that they are not something you should trust on a daily basis, no matter what some governing body states. Even measuring typical mains voltages a homeowner should have safety glasses along with insulated gloves and shoes, then only use one hand to take the measurement. If you go around using two hands to shove test leads into sockets on a regular basis without a second thought, then the one day you do it out of habit with wet hands and some test leads that maybe have some cracks in the insulation, you're going to have a bad day.
Of course if you're in the industrial space, you are going to be schooled up on proper PPE for this stuff, so honestly the ratings on the test equipment don't even matter for your personal safety, IMHO. Multiple protections will have to fail before there is an incident. So maybe measurement device protections, PPE, good habits, and maybe even a buddy to get help just in case!
BeBuLamar:
--- Quote from: bdunham7 on December 02, 2022, 12:50:07 am ---
--- Quote from: Traceless on December 02, 2022, 12:15:16 am --- Long ago I 'blew up' my unfused Mastech-built Harbor Freight meter by the time-proven method of testing a wall socket with the lead in the amp jack. Blew the traces off the board, burned up the test lead and wall socket and tripped the breaker. Both I and the meter survived (with repairs) but the wall socket didn't. I now have a meter for electrical work that makes this impossible (Fluke 116).
--- End quote ---
I wonder what happens if one try to measure voltage with the 116 and the dial is set at microamp position?
--- End quote ---
2N3055:
--- Quote from: Traceless on December 02, 2022, 08:21:37 am ---At first glace that seemed like pretty horrible design safety-wise. If you look at the specs more closely though, they say that the DC µA range of that meter has a burden voltage of 3.5mV/µA aka. 3.5kV/A which is pretty high. Still DC µA will create a short across the mains and there is a lot of energy involved...
--- End quote ---
No it will not create a short on mains. It's internal resistance is equivalent to 3500 Ω in that mode. At 240 V that is 70mA. And there are protection circuits to limit current going into the meter. Brymen says it is protected up to 1000V.
And amount of energy in mains voltage is directly related to where are you measuring. That is what CAT categories are all about.
Your socket inside normal office or apartment will pretty much make medium loud "poof" when shorted, without much drama.
Doing that on 400A master fuse going into the building (with wires as thick as your finger) will be different story..
I would hope people would not play there if they are not certain what are they doing.
It is all about available short circuit current...
mqsaharan:
--- Quote from: Traceless on December 02, 2022, 10:54:44 am ---
--- Quote from: mqsaharan on December 02, 2022, 09:52:01 am ---Also, their design choice of using 2xAA for a chip with 2.5V low battery threshold (2.85V low battery for Cap and Hz), in my opinion, is a poor choice. There is a little mistake in the manual regarding 2 captive screws on the battery cover. The picture on the next page clearly shows that there will be only one. Anyway, not important.
--- End quote ---
Yes that is not great but can probably be mitigated a bit by using 1.7V lithium-AAs.
--- End quote ---
You specifically mentioned 1.7V lithiums. I guess you are going to discharge them a bit or put a schottky or germanium diode in series with them. Because some meters like Brymen 235 don't accept them. At least they'll not leak.
--- Quote from: Traceless on December 02, 2022, 10:54:44 am ---
--- Quote from: mqsaharan on December 02, 2022, 09:52:01 am ---I particularly liked the high sensitivity mode for phase rotation measurement for motors. It is a unique feature.
--- End quote ---
This is indeed a cool feature but not the only nice trick that meter has up its sleeve. It also supports 1-lead-contact-phase detection and thus can replace a voltage-tester and enable you to find the phase even without access to a ground terminal.
--- End quote ---
I haven't used many meters personally but a few meters that I have used so far that have high input impedance can do that trick (shows higher voltage when input jack is connected to phase than to the neutral).
--- Quote from: Traceless on December 02, 2022, 10:54:44 am ---
--- Quote from: mqsaharan on December 02, 2022, 09:52:01 am ---Edit: Oh, I forgot to mention that in my humble opinion, it is always best to use fused probes like Fluke FTP with industrial mains regardless what meter someone is using.
--- End quote ---
Fused probes would be nice, but I took a look at the Fluke FTPs and they cost almost twice as much as the Brymen including accessories :o.
--- End quote ---
Sorry about that. I used it only as an example and suggested only for industrial work. There are a few other manufacturers in Europe offering fused probes, fused leads and even small fused attachment that connects directly to the meter and accepts normal probes.
HKJ:
--- Quote from: mqsaharan on December 02, 2022, 10:13:59 am ---He is talking about uADC function, which is, as per manual, using input jacks for measurement. Thus the concern regarding the safety of the user and meter when there is no mention of fuse in its literature.
--- End quote ---
A uA range can/will piggy-bag on the same protection as the ohms ranges, it is basically the same current. Only disadvantage is that the burden voltage is higher than on a traditional uA range with a fuse and diodes.
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version