Products > Test Equipment

Big Clive's "Trashy" meter, unboxed ( Duratool D03047 multimeter )

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Someone:

--- Quote from: joeqsmith on April 27, 2023, 12:39:49 am ---
--- Quote from: Someone on April 26, 2023, 09:38:58 pm ---
--- Quote from: joeqsmith on April 26, 2023, 01:07:57 pm ---
--- Quote from: Someone on April 26, 2023, 07:43:45 am ---Every mains socket outlet is CAT III, ...
--- End quote ---
Provide a reference in any of the IEC standards from any country that states that.
--- End quote ---
I quoted the AS61010 standard in the other thread that this has split into. Not having any of the international examples to hand at the moment that will do, and you're free to provide quotes from others.


--- Quote from: Someone on April 26, 2023, 11:03:53 am ---61010 measurement categories are really simple:
"CAT III is for measurements performed in the building installation"
--- End quote ---
Good luck trying to argue that a mains socket affixed to the wall is something other than the building installation. But we have several people trying to be "clever" and say either side of the socket outlet should be treated the same, when the standard says that is the point of distinction.

--- End quote ---
My home has a tiny little service coming into with a small distribution transformer.  Nothing like the feeds for the buildings where I worked.    Outlets at my house are several feet from the main feed and are behind small CBs which is behind another small one.  Worse thing that will happen if I pull and outlet and short the wires, I blow a breaker.  Hardly CAT III or risk of an arc flash.       

Even at work where we have larger services to plug into, it's a long way from the main lines and again fed though various CBs.  Lots to limit the current.  Some of the larger factories I have worked will have their own distribution systems outside in fenced areas. 

I'm not going to get all concerned about my home toaster repairs and my CAT III outlets because it's just not the same thing.
--- End quote ---
So what's the supply impedance at those socket outlets? Because over here we do see impedances at the outlets low enough in residential installations to require >1kA breaking capacity in a meter hence the need for at least CAT II for mains connected devices. I've not worked on or measured a high current residential supply with lower impedances, but with electrification of vehicles they will become more common and then you're into the CAT III fault currents (100A 2% droop) before considering transients/faults.

Yes, it may well be that there is no need for the higher ratings of CAT III somewhere (or anywhere) between the socket outlet and the supply feeder in your installation, that will vary from location to location. I'm not disagreeing with that but the standards have to cover a huge range of possible situations and almost (but not guaranteed) worst cases so most real world examples will be far below the limits. The standard is a way to have a quickly and easily understood delineation point, which you and others are going to great lengths to try and muddy/blur/confuse for some unknown reason.

IanB:
I have a small question for everyone in this thread: do your lightbulbs have a CAT rating on them? When you twist a bulb into its socket, do you ever worry about it exploding in your hand? Do you wear safety glasses and rubber shoes when you change a lightbulb?

A DMM may be connected to the mains for a few seconds at a time to take a reading, and there is only one of them. All the lamps in your house are connected to the mains 24/7 and switched on for hours at a time. They could explode, cause a fire, or cause human injury. The risk is vastly higher than with using a DMM.

Why are there many threads about meters, and no threads about household appliances and electrical devices? There are millions more of the latter, and a proportionately higher hazard, statistically.

EEVblog:

--- Quote from: IanB on April 27, 2023, 02:34:25 am ---Why are there many threads about meters, and no threads about household appliances and electrical devices? There are millions more of the latter, and a proportionately higher hazard, statistically.

--- End quote ---

Because engineers like to nitpick about test equipment.

EEVblog:

--- Quote from: joeqsmith on April 27, 2023, 01:18:44 am ---
--- Quote from: EEVblog on April 27, 2023, 12:53:36 am ---The robustness of bench meters is effectively stamped on the front. Both of mine (Keithly and Keysight) are CAT II 300V. That screams "I'm delicate please don't hurt me!"
No need for testing, just assume all bench meters are delicate snowflakes.

--- End quote ---
Or test them to a common standard and see how they shake out which is what David is asking about.   No big deal to benchmark them.   

--- End quote ---

Sure, but I'd bet few people would care. It's not like you'd use that as a buying decision for a 4 digit priced bench meter.
And if you thought there are a lot of people complaining about blowing up DMM's is pointless, wait until you blow up expensive high end bench meters.
But hey, knock yourself out.

Someone:

--- Quote from: IanB on April 27, 2023, 02:34:25 am ---I have a small question for everyone in this thread: do your lightbulbs have a CAT rating on them? When you twist a bulb into its socket, do you ever worry about it exploding in your hand? Do you wear safety glasses and rubber shoes when you change a lightbulb?

A DMM may be connected to the mains for a few seconds at a time to take a reading, and there is only one of them. All the lamps in your house are connected to the mains 24/7 and switched on for hours at a time. They could explode, cause a fire, or cause human injury. The risk is vastly higher than with using a DMM.
--- End quote ---
I wouldn't change a light bulb unless the switch is turned off, no I don't tag out or prove the circuit de-energised but that works 99.999% of the time (yes I have been shocked from that approach and faulty power switch). Equally I wouldn't put my face near a lamp when powering it on for the first time, proximity to a handheld multimeter is generally very different.

Electrical fires in appliances/cabling, yep that happens more often.

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