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Posted By: Andrew CAT ratings on multimeters. - 10/01/03 02:54 PM
I'm just getting back into industrial work and I see that Fluke keeps pushing their CAT ratings on their meters. I have an older Fluke that works just fine but doesn't seem to be CAT rated. It seems like it is some safety standard. Can anyone help me understand whether this is important or whether it's just another marketing gimmick? Are other meters CAT rated?
Posted By: rmiell Re: CAT ratings on multimeters. - 10/01/03 03:23 PM
I'm not sure, but the CAT ratings must be for the ability to interface with a computer, via one of the rated cables (CAT 3, CAT 5, CAT 6), in order to download info to a software program. If you are not doing this, then the rating is useless to you.

My opinion only.

Rick Miell
Posted By: ThinkGood Re: CAT ratings on multimeters. - 10/01/03 04:00 PM
I believe it has to do with overvoltages:
http://relays.tycoelectronics.com/lexicon/Overvoltage.stm
Posted By: Redsy Re: CAT ratings on multimeters. - 10/01/03 04:00 PM
The rating pertains to how close to the utility line you may be while using the meter.
I believe CAT1 being suitable for branch circuit measurement, CAT4 being suitable for measurement right at the secondary terminals of a distribution transformer.
The others, somewhere in between.


[This message has been edited by Redsy (edited 10-01-2003).]
Posted By: Bjarney Re: CAT ratings on multimeters. - 10/01/03 07:25 PM
Er, Fluke ain’t makin’ this stuff up. It’s evolved from UL Standard 61010B-1. The various “CAT” ratings are installation/overvoltage categories with Category III and IV having the highest overvoltage withstand.

One way to look at it... The higher the circuit voltage and short-circuit capability where the meter is applied, the higher the needed CAT rating. {It's nice if the meter in your hand does not vent flames or detonate in the process of checking voltage in a live panelboard.}




[This message has been edited by Bjarney (edited 10-01-2003).]
Posted By: Bjarney Re: CAT ratings on multimeters. - 10/01/03 07:36 PM
Aside — The “CAT” installation-/overvoltage-category ratings here are not the same as that for bandwidth in EIA/TIA 568 datacomm wiring.
Posted By: Bjarney Re: CAT ratings on multimeters. - 10/01/03 08:01 PM
UL’s stated objective of “1010” is to: …provide adequate protection for the OPERATOR and the surrounding area against:

- electric shock or burn;
- mechanical hazards;
- excessive temperature;
- spread of fire from the equipment; …
- liberated gases, explosion and implosion.



[http://ulstandardsinfonet.ul.com/scopes/61010B-1.html]




[This message has been edited by Bjarney (edited 10-01-2003).]
Posted By: iwire Re: CAT ratings on multimeters. - 10/01/03 09:02 PM
Quote
{It's nice if the meter in your hand does not vent flames or detonate in the process of checking voltage in a live panelboard.}

You safety minded folks take all the fun out of being an electrician. [Linked Image]

Fireworks are beautiful any time of the year. [Linked Image]

OK, I admit it, I have a Category III. [Linked Image]
Posted By: Bjarney Re: CAT ratings on multimeters. - 10/01/03 09:27 PM
Those miniature 250V glass fuses in some multimeters will very effectively make your ears ring during unintentional 480V “interruptions”—believe me. They may also bring rapid and unwanted attention from superiors—and not of the “atta’ boy” variety.
Posted By: iwire Re: CAT ratings on multimeters. - 10/01/03 09:41 PM
Kidding aside I think we can forget that using any meters can be dangerous.

Someone I know received some serious burns on both hands from a phase rotation meter.

Apparently the 3 permanently attached leads where they entered the meter had a short in them from years of use and probably abuse (carrying it by the leads)

Now of course he should have had PPE on but this goes back to forgetting that S*** can happen even when doing the most mundane tasks.
Posted By: Trumpy Re: CAT ratings on multimeters. - 10/02/03 05:51 AM
From IEC 1010:
  • Cat I: Signal level, special eguipment or parts of equipment used in telecommunications or electronics.
  • Cat II: Local level mains, appliances and other portable equipment
  • Cat III: Distribution level mains, fixed installation wiring.
  • Cat IV: Service drop wiring to building(outside).

Personally, I'd never use a DMM for any thing closer to the Distribution wiring than the Main switchboard and I would most certainly not use one to test the incoming mains on the pole or at the metering.
IEC 1010 also does mention that DMM's used
for Electrical testing, must have the inputs marked with a certified Cat rating on them!. [Linked Image]
Posted By: bigrockk Re: CAT ratings on multimeters. - 10/04/03 02:12 AM
This might help: http://www.electricsmarts.com/content/testers_multimeter.asp
Posted By: Trumpy Re: CAT ratings on multimeters. - 10/04/03 06:33 AM
bigrockk,
Thanks for that link!. [Linked Image]
Having said that, I would never use a multi-meter to test anything more than appliances while they are live.
I normally use Duspol solenoid testers above 230V and for 400V work.
Above this I use a Modiewark for Voltage sensing at voltages 3.3kV-66kV on the end of a Hotstick.
I also have a Phasing out set, for use on 3.3- 66kV.
You have to be Verycareful working with High Energy circuits, these things really pack a punch if wrong connections happen!.
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