Electrical Measurement Categories - CAT I II III IV
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- čas přidán 22. 03. 2015
- Measurement categories for electrical measurement equipment such as multimeters.
CAT I equipment is not suitable for connection to the mains supply, CAT II and above is, but the distance from the energy source is important, with CAT IV being nearest to the energy source such as where power enters a building.
Arc Flash video: • 480 volt 3-phase Arc F...
Website: xo4.uk/?KaT - Věda a technologie
I spent ages trying to find out what the classes meant. You've nicely cleared it up in a concise manner.
You are a credit to youtube and your videos are very informative. keep them coming please.
Thank you for this vital piece of info, John. I didn't realise how dangerous a short at the mains cutout could actually be, nor did l realise the 'actual' importance of the CAT I,II,III,IV measurements.
The voltage indicator (which says that it is GS38 compliant) that l use was provided to me by a reputable online company, yet does not have a CAT listing on it at all.
It came free when l bought an Metrel Easitest MFT, which definitetly does have a CAT label on it.
But as for the voltage indicator, It states all the various values on the back of the unit but doesn't have a CAT label on it anywhere (including the probes). Nor does it have a manufacturer's name on it anywhere, which l think is very strange.
It defintely looks the part but after watching some of your videos,I'm now highly dubious regarding this device which l use all the time to prove for dead.
I think that its maybe time to upgrade.
Thanks again, John...
Your little Arc Flash Video sent me on a 3 day CZcams follow up clip rabbit hole.
And also worth noting is just because you have a cheap multimeter with say CAT III printed on it doesn't mean that it actually is rated for CAT III. They can basically print on anything they want.
as always the Brits are able to explain things in 10 min and its clear concise and makes sense were the Americans still are trying to explain it to themselves
thanks for the information it as usual has taught me allot
Just to add....... In relation to arc-flash, although I have seen that video that you have linked-to and it being a controlled arc-over, I also found another video where a person was actually killed by an arc-flash.
It turns out that he done multiple no-no's in a power distribution room: He opened a cabinet to find a fault. Although the doors were interlocked and could only be opened with the isolator in the OFF position, once he opened the door, he closed the isolator again, meaning that everything inside the cabinet was live again and exposed.
He then forgot the voltage of the cabinet he was working on. Taking his multimeter to check the fuses in the cabinet (which was probably rated for a maximum of 1000v) he then proceeded to probe away in the cabinet.
There was a massive blast. It didn't kill him instantly, but he did die from his injuries.
It turns out that he was probing away inside a 2300 volt cabinet with a multimeter rated for a maximum of 1000v.
Investigators found the remains of the multimeter on the floor right by the cabinet he was probing. It was completely unrecogniseable and looked like it was in a few pieces, so the multimeter (which was sat on the floor between his knees) probably exploded there and then and also conducted down to earth.
He also wasn't wearing a face shield. Being only at arm's length from the source, (instead of a fair distance away with the properly-rated hot-sticks) when the blast went off, he took the full force right in his face.
He was also working alone when instead, there should have been a crew of at least two in the distribution room. He also failed to notify anyone that he was entering the distribution room, hence why he was in there alone.
Link: czcams.com/video/hfnEuRA7-vo/video.html
-BoomBoxDeluxe.
Thank you.
This video was perfect, Helped me greatly understand, never played around with house wiring the multimeter, Only stuff for my Arduino, which I guess don't even get classed as CAT 1 once ran on batteries. Again, thank you very much.
Great video John very informative! 👍🏼
Not just the current range that it applies to- also the voltage ranges.
The 240v is the *nominal* voltage but everytime something is switched off, that current wants to keep going- due to inductance. It produces a short lived spike in the voltage, potentially many thousands of volts.
Higher up the chain means more current flowing in a given wire, means those excursions are larger when they occur.
A 600v cat IV needs to survive an 8000V transient, vs 4000V for a cat II
Very useful information.
Thanks for the very informative videos. They have been very helpful. Keep up the great work.
fantastic series of videos clear and informative 10 out of 10
LOVE THE FRAMERATE OF THIS VIDEO
Hi John thank you very much ref borehole motor cable. You have confirmed my own thinking.
i never knew and now i do, thanks John
Great video. Very interesting.
AWESOME Content
Hi John, I was wondering would you recommend MCB testing and if so How?
as I understand it there are 2 bits inside A typical MCB,
the 1st bit reacts to over heating ( bi-metalic ) and the 2nd uses magnetic flux both driven by the fault current!
question is how does one replicate real world conditions and test them!
I don't fancy messing about with resistors and I have a healthy respect for low impedance mains!
perhaps the charge capacitance of a large capacitor could be utilized to create a large pulse! and do it as a dead test.
stoned again
kind regards
our consumer unit is right next to the meter and the providers fuse with a very small length of cable between them in this situation would the consumer unit be a cat iv?
I took basic electricity at the local community college. Recently, I have an opportunity to apply what I have learned to an actual job. The position requires a CAT ll certification. Your definition is clear but am still wondering what might be on the test when electrical properties are the same for all categories. I was able to check my personal volt ohm meter, and I discovered that I have one rated for category lll. I didn't even realize that the caps came off but it makes since for arcing scenarios.
very useful videos
plugged in rubbishy probes awesome john ward
Nice explanation, Thanx for showing,
-BoomBoxDeluxe.
_6th April 2015, 02.54_
Legend clever guy John
Thanks for the clear no fuss explanation.
I bought an LCR meter with cat 2 rating and max to ground of 60volts.
Does that fit with what you said about televisions having 100s of volts stored say in capacitors ?
Im interested in fixing cassette decks that have audio noise or dim displays.
.
Appliances are CAT I, so CAT II meter is fine for those.
Capacitors need to be discharged before testing as when charged they can damage some meters, and for the high voltage ones they can cause injury.
I want to use a multimeter for household devices and my projects. Will a multimeter of CAT 3 work or a multimeter of CAT 2 + CAT 1 is needed? Will there be any difference in measurements?
You are topman J.W.
Thanks for the video =)
Thanks John, I appreciate your videos. 02DEC2017
The categories on testing equipment means that if there is a fault the test equipment will not explode or go on fire if thee is a fault, if used in the correct category area?
whats the scenario where at cat 3 600v would fail and a cat 4 600v would survive especially for voltmeters
Hi John can you plse advise cable size from dist board 115 metres to pump house and 100 metres down to borehole for water pump in Africa. The cable from dist board to pump house will be underground for protection reasons. Many thanks
Sorry John forgot to mention motor is single phase 230 volts and 1.5hp thks
4mm² based on the likely running current, although 6mm² may be better depending on the type of motor. Voltage drop is the main issue here - if the voltage drops too low, the motor may not start.
So if I connect 100 9Volt batteries in series, that's Cat I?
i see a cheap multimeter the probes are molten and vaporesaded and the multimeter is exploded under messering 400V on setting 10 amps :(
Oscilloscope CAT I, probe CAT II can you measure mains?
In theory yes - although use of an isolation transformer to power the device under test is essential to avoid the possibility of shorting out the mains supply and destroying the oscilloscope.
Another consideration is that the scope inputs will have a maximum voltage, and that is peak voltage, not AC. 240V AC is actually nearer to 340V peak. 10:1 or 100:1 probes are normally used, so that the voltage at the inputs is far lower, and it's also essential that the probes themselves are rated for the voltages being applied to them.
Some mains supplies can be noisy and have larger voltage spikes on them, so even with the correctly rated probes, voltages can still exceed the rating of them.
What make are the probes with the caps?
cumberland1234 Cheap TENMA ones from CPC, cpc.farnell.com/tenma/72-9340/test-leads/dp/IN06175
***** cheers
+John Ward Well done J.W.
Very good video, thank you!
But I wouldn't use a multimeter for measuring in the mains. First they have a too high impedance, you'll see a voltage (aprox. 60 up to 90V) where is actually none (reactive voltage through capacitive coupling). And you'll have to turn away your sight from the testing point to read the indication of the multimeter. Standing on a ladder and try to measure voltage with a multimeter is not very comfortable.
That's the reason why they are not allowed in the german regulations to use them to test if a circuit is de-energized, only 2-pole voltage testers are permitted.
I knew a guy that had a CAT V wife. They called him ol' no spark Finton.
be carefull! at my parents the meter is direct next the fuse box! 4 times 70 mil come in!i think all under cat4 does not poke into mains! i have a socket 1 phase and 3 pahse 63 amps next my fuse box!
Niceeeeee
Why does the meter care? If things become unsafe at 600V CAT3, why is it suddenly safe for 1000V CAT2? It's not like it's any different. voltage is voltage after all. If it arcs it arcs at a certain voltage for a given distance (and air pressure, moisture, etc). The meter is connected by leads, and everything internal is fixed. So I don't understand.
The only problem I can see here is with the amount of power something can deliver. But that's a function of voltage and current. P = U * I. But even 1V can melt your leads and meter at 100A. It wouldn't kill you of course, but then again it was 'safe' to put across your 600V rating. So what's the deal with that?
The difference is the amount of energy available. A short circuit fault within an installation will have a relatively low amount of energy due to the impedance of the circuit cabling, the same fault at a main distribution board will have far more energy as the impedance is much lower.
Not so much for 600V cat iii Vs 1000V cat II.
But there's also the matter of transients- whenever a current is interrupted by being switched off, it produces a momentary spike in voltage, due to inductance in the system, potentially 1000s of volts but for a brief brief period of time.
Wires higher up the chain are carrying more current, and thus the spike can be higher if it does occur. Higher level meters must be rated for larger spikes, even at the same voltage.
another eg. on arcs: czcams.com/video/6hpE5LYj-CY/video.html
John I do not agee with you, most of multimeter CAT refers to overvoltage cattegory not short cicruit current. Look for category explanation Fluke ABC of multimeter safety. BR.
Yes, the rating is based on the voltage not the current although it is related to the circuit impedance and therfore prospective fault current.