Products > Test Equipment
Multimeter CAT II Rating Discontinuation
bdunham7:
--- Quote from: alm on July 25, 2023, 11:39:44 pm ---Overvoltage ratings are about safety, not the ability to measure. Maybe some internal amplifier would clip, the accuracy would be severely degraded due to V^2/R heating in the divider, or maybe it would even be damaged if exposed repeatedly to 1000 Vrms but not harm the user. Again, IEC 61010 does not care if the equipment keeps working or dies as soon as you turn it on. It's a safety standard, not a quality standard.
--- End quote ---
I don't know what is in the current regulations, but I recall seeing quotes or references to specific language requiring the meter to be able to detect and display the presence of hazardous voltages even after the transient test. There was some discussion about degraded accuracy and such, but this is clearly a safety issue as well--if a transient can suddenly cause the meter to display 000.00V when the circuit is still live, that's not good.
I think it is likely that manfacturers could interpret all this in different ways, and one takeaway point is that just like with accuracy specifications, it is not very helpful to directly compare instruments from different manufacturers solely by their specified ratings.
From a Fluke advertorial:
In the impulse testing phase, Fluke multimeters are subjected to repeated jolts of high voltage to prove they can withstand voltage spikes from lightning or other causes without damage to the product or harm to their users. The higher the voltage or measurement category where the product will be used, the higher the test voltage applied—up to 12,000 volts for products designed for CAT IV/1000V environments
https://www.fluke.com/en/learn/blog/safety/fluke-lab-tortures-test-tools-so-technicians-feel-no-pain
bdunham7:
--- Quote from: tautech on July 25, 2023, 08:51:20 pm ---Normal industry ratings.
1kV rated meters generally max out at 750VAC.
--- End quote ---
I get it, I've seen many and I'm used to it. I think it is unhelpful and especially confusing when you have a CAT I/1000V rating and the separate AC measurement limitation is not on the face of the meter. If you have to read the manual to know something as simple as the maximum voltage rating, that's not optimal.
tautech:
--- Quote from: bdunham7 on July 25, 2023, 11:55:44 pm ---
--- Quote from: tautech on July 25, 2023, 08:51:20 pm ---Normal industry ratings.
1kV rated meters generally max out at 750VAC.
--- End quote ---
I get it, I've seen many and I'm used to it. I think it is unhelpful and especially confusing when you have a CAT I/1000V rating and the separate AC measurement limitation is not on the face of the meter. If you have to read the manual to know something as simple as the maximum voltage rating, that's not optimal.
--- End quote ---
Yet operating the meter beyond ratings is normally met with OL on the display.
One normally expects those playing with such voltages have some idea what they are doing.
How much need a manufacturer hold the hand of their users ? :-//
Martin72:
Actually, not at all, it is enough to indicate to what extent you are allowed to use the device.
I don't know where it is regulated differently, but here only trained electricians are allowed to measure voltages that go beyond what is just not life-threatening.
Someone:
--- Quote from: bdunham7 on July 25, 2023, 11:38:15 pm ---It the standards are vague enough to allow some manager somewhere to claim that the CAT II bench meter is good enough for the scenario I laid out, then they aren't helping much. But I'm a bit doubtful that they would be that flawed or that Fluke would deliberately (or even negligently) publish false information that clearly contradicts what you are claiming is the standard. My best guess, based only on speculation and language from Fluke's reference, is that there is additional language specifying a single-phase receptacle/plug, not just any receptacle/plug.
--- End quote ---
You're on point here, the standards do not have a string of complex clauses for the definitions of Measurement Categories, its laid out plainly as I provided direct word for word quotes of.
Yes, the delineations are not perfect but there is no perfect delineation as the world is complex. This is layers of abstraction as the Measurement Categories define the limits of the safety tests, so all that compliance to a specific Measurement Category defines is that the product won't cause a hazard within those defined synthetic test conditions..... which have been chosen by the committees based on historical data and experience to generally cover the real world situations.
Why is it so hard for people to understand????
The standard is a specific limit that is considered representative of the real world.
There will be real world examples worse than that (but they will be very few/unusual)
There will be real world examples that are benign and never even approach the limit (common, routine, normal, typical, most situations)
Otherwise you end up with an impossible to meet standard that covers a soaking wet gorilla probing a socket outlet outside in the rain, which is connected back to the poles with some obscure 120mm2 cable, during lighting strike on the nearest pole.... and the meter needs to continue operating perfectly afterwards despite being on current mode and connected across the phases.
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