Why CAT ratings are so important AND safe practises

[Assafl]

So CAT ratings are important. Education is more important but without education people only have CAT ratings to help guide them. Companies that lie about safety ratings of their products should be fined, and/or closed down.

Disagree with the first point. If Cat rating provide guidance - Absolutely nothing about my Cat IV 600V / Cat III 1000V rated Agilent makes me qualified to open a distribution panel, an industrial breaker cabinet or an elevator control panel - Absolutely Nothing. If it is guidance it is absolutely false guidance.

And nothing about using the DMM will protect me or my life. Maybe an arc flash (or worse) won't happen - but there are other things that can burn and blow up when I short the 380V delta that can hurt me. And who says that the DMM (that guided me to the foolishness in the first place) would cause the demise? Maybe it is the uninsulated (non rated) pliers that fall, short the bus bars and vaporize? Maybe it is a finger that wanted to feel the curly heat dissipating braking resistor (not realizing that the huge resistors are not insulated).

So if a Cat is mentioned, or if there are symbols of DANGER in red and Yellow and if there are signs that the equipment is powered from multiple sources or has Arc Flash warnings - the beginner is not qualified to touch it. Not even open the cabinet to have a look inside. It matters little what DMM they have and what guidance those DMM offer.

Companies that lie about safety should be shut down? maybe. But currently it seems they are rewarded by having more customers.

NB - What comes to mind is that if indeed you are right and multimeter marking become construed by beginners as "guidance", and OSHA (and others) identify a trend that "beginners" probe and blow up industrial cabinets with "safe" multimeters - that in itself is good enough reason to restrict Cat III and Cat IV multimeters to licensed electricians.
I hope the concept of "guidance" provided by IEC61010 is just wishful thinking (or a concocted rationalization to buy a more expensive multimeter) rather than a reality. BTW - a bit intrigued I waded through a couple of Fluke brochures: The Cat ratings are not used as marketing to beginners. Only to electricians. So not everyone uses this approach of "guidance".

[Lightages]

Huh? What did say? Oh let me repeat myself: "Education is more important".

[Assafl]

Huh? What did say? Oh let me repeat myself: "Education is more important".

Huh? What did say? Oh let me repeat thyself: "Education is more important but without education people only have CAT ratings to help guide them."

No it isn't. Without an education, and even with an education (if they didn't pass the exam) Cat is of absolutely no guidance to them. They shouldn't be near an Arc Flash area, let alone probe one.

[Lightages]

You are making straw man arguments. When did I ever say that people should look at a multimeter rating and then decide they are experts in high power distribution? If you don't have the education to understand how a multimeter is falsely rated and still try to climb the utility pole and measure the input to the transformer, then CAT ratings and education won't help. You are an idiot.

I said "help guide them" not be their only information on how to use a multimeter in any situation.

[b_force]

Wait, whaaaat?
Are now people who're actually agreeing with each other actually f.. ...fighting each other? 

I guess this is a good definition of miscommunication 

[Assafl]

Wait, whaaaat?
Are now people who're actually agreeing with each other actually f.. ...fighting each other? 

I guess this is a good definition of miscommunication 

There is nuance in the discussion: We both agree that a rated, tested, reliable DMM is better. And we both own such meters.

But does a beginner need one? Assuming one cannot afford one (or won't be willing to spend on one) is it better to use a simple "just insulated to 300V" DMM or (the alternative) run blind without a DMM at all.

Some would say that it is essential. If you are a hobbyist you must own a entry level Fluke or Brymen or Escort or the like. The alternative is to work without a DMM (run blind) or not be in the hobby.

I (and several others) think that running blind on live circuits is far riskier than using a less than perfect DMM (Cat 2 rated or insulated to a few 100's of volts). Hopefully they like the hobby and upgrade to something better soon.

[joeqsmith]

Interesting read.  I did not understand EEVBLOG was for hobbyist only and that hobbyist did not care about CAT ratings.  Learn something new every day.   

Nothing I have not posted before but for my home hobby electronics, I care very little about the CAT ratings.  I'm more interested in a meter's ability to survive some basic transients.  I don't work on anything at home where arc flash would be a concern.  That said, looking at the meters produced by major brands that have been certified to meet the EMC and safety standards have certainly proven to be some of the most robust meters I have looked at.   So in that regard, these higher end meters do give me some comfort that they will survive most of what I would throw at them.    I don't think a higher CAT rating guarantees a meter will be robust, even if it has been certified.  I've seen some pretty high end meters flop at some pretty low levels.   Some are taken out with nothing more than a little static discharge.  And certainly I know that if I turned stupid and started trying to measure the output of a MOT that even the most robust meters I would not expect to survive. 

Of course, if I were only using <50V, I would not even care about the electrical robustness beyond some basic ESD handling.  Electronics is such fun.  So diverse.  It never gets old.

[nctnico]

I think you have to seperate between two uses:
If a DMM is going to be used on household mains then do yourself a favour and get a CAT rated one from an A brand like Fluke or Keysight.

If a DMM is going to be used on low voltage (<=48V) and low current electronics then you can use any DMM you like.

The user being aware of the dangers is a totally different story. Simple rule: 'don't mess with mains unless you have had and education/training so you know the rules and dangers'.

[Mr. Scram]

This is what happened to the CatIV 600V rated Fluke.



There is this "below the radar" trend on EEVblog to tell beginners to get a CatIII or a CatIV Expensive (called by proponents "independently certified") DMMs and that these DMM will "save them" when they fool around probing in a wanton fashion (since they are beginners). Eddie was not a beginner (at least not according to the employees interviewed) but used his expensive Fluke on a >2000V 1200A starter equipment.

Carelessness is never rewarded by electricity. At best really expensive components release the magic smoke. At worst, the careless EE does. A careless beginner should take up sawing or embroidery. Or stick to "Arduino on Battery".

BTW - A regular, fused home circuit (15A, 20A, etc.) cannot sustain what took place there. Neither the current capability nor the voltage.

Why is this used as an example how a good meter won't save you? It's a situation an at home hobbyist will simply not encounter.

[Mr. Scram]

I think you have to seperate between two uses:
If a DMM is going to be used on household mains then do yourself a favour and get a CAT rated one from an A brand like Fluke or Keysight.

If a DMM is going to be used on low voltage (<=48V) and low current electronics then you can use any DMM you like.

The user being aware of the dangers is a totally different story. Simple rule: 'don't mess with mains unless you have had and education/training so you know the rules and dangers'.

The problem is that a beginner doesn't always recognise dangers correctly. A good meter helps keeping him safe. Elsewhere, someone gave a car battery as an example. It's just 12 volts, but a lot of amps, and might easily catch a beginner out.

There are always ways to stupidly hurt yourself, but making inevitable mistakes hurt less is key.

[b_force]

I think you have to seperate between two uses:
If a DMM is going to be used on household mains then do yourself a favour and get a CAT rated one from an A brand like Fluke or Keysight.

If a DMM is going to be used on low voltage (<=48V) and low current electronics then you can use any DMM you like.

The user being aware of the dangers is a totally different story. Simple rule: 'don't mess with mains unless you have had and education/training so you know the rules and dangers'.

The problem is that a beginner doesn't always recognise dangers correctly. A good meter helps keeping him safe. Elsewhere, someone gave a car battery as an example. It's just 12 volts, but a lot of amps, and might easily catch a beginner out.

There are always ways to stupidly hurt yourself, but making inevitable mistakes hurt less is key.

And similar to my previous post on the previous page, I don't agree on this statement at all!
In fact, I believe it's very dangerous advice.
A good meter, or machine or whatever doesn't safe lives!

If the situation is so dangerous for a beginner something else than the meter would be already a much bigger problem.
Especially if you don't recognize the dangers!

But like other people already mentioned, a normal 'hobbyist' will never ever enter those high CAT rated situations.
Why? Because you're simple not allowed to enter these areas without permission (actively checked, or passively secured) 
Maybe, but just maybe, the only potential dangerous situation, is working on your own fuse/distribution board/box. which is allowed in some countries, the rest is all CAT II and CAT I.
If you do anything else, I think (but correct me if I'm wrong) you're in violation and probably committing a 'crime'.
So if you do harm to yourself or someone else, you have a very big problem anyway.
Which automatically solves the whole issue.

[Mr. Scram]

And similar to my previous post on the previous page, I don't agree on this statement at all!
In fact, I believe it's very dangerous advice.
A good meter, or machine or whatever doesn't safe lives!

If the situation is so dangerous for a beginner something else than the meter would be already a much bigger problem.
Especially if you don't recognize the dangers!

But like other people already mentioned, a normal 'hobbyist' will never ever enter those high CAT rated situations.
Why? Because you're simple not allowed to enter these areas without permission (actively checked, or passively secured) 
Maybe, but just maybe, the only potential dangerous situation, is working on your own fuse/distribution board/box. which is allowed in some countries, the rest is all CAT II and CAT I.
If you do anything else, I think (but correct me if I'm wrong) you're in violation and probably committing a 'crime'.
So if you do harm to yourself or someone else, you have a very big problem anyway.
Which automatically solves the whole issue.

It's not a binary thing. A good meter creates more of a buffer between the user and serious hurt. A bad meter makes that a more narrow area. No one supposes that magic meters exist that prevent any and all harm, but by creating that buffer, they will save people's butts.

Again, a car battery is a decent example how a beginner might get himself in trouble. A good meter will blow a fuse, a bad meter might cause serious heat of cause an actual fire, and the performance of in-between meters may vary.

[Lightages]

To be clear, once again, I said that education is better than anything else. CAT ratings are there to help people be safer. If you don't have any education then you should have a properly rated meter that helps, HELPS, mitigate wrong use.

The proper CAT rating for a home user who has the opportunity to test a wall outlet is CATIII 300V, minimum. CATII is to be used on any circuit that is at least 10m from the distribution panel. How many houses have all of their outlets further than 10m from the distribution panel? The requirement for CATIII is not mine, it is in the IEC standards.

If you have the education or experience to understand the limitations of a multimeter, regardless of its rating, then use what you are comfortable with. You are taking an educated risk. If you don't have the experience or education, then you should follow the guidelines and/or regulations that are put there to help keep you safe. These regulations also will help save you money in some circumstances. Meters melting down instead of blowing a fuse, cost money. Meters that are made to high standard that can pass CAT ratings, truthfully, also are more likely to be higher quality and be a better buy for the money.

The assertion has been made that poor people do not have the "luxury" to buy properly rated equipment. A quick search found a multimeter for less than $30 that is CATIII 600V with third party certification. The Amprobe AM-500.
http://content.amprobe.com/certifications/AM-500_CSA.pdf

So if your life or safety is only worth $5, that is up to you, whether you make $5 per day or not. Just know what you are getting into, education, remember? IMHO, better to spend another $25 and have a better time for me overall.

[Assafl]

I think Dave had an interesting experience with a CatIII 600V rated Extech (Flir systems) Tweezers that blew up in his hands.

If my memory serves me right Dave discovered there was a design flaw in a switch that the probes pressed against. While I think Extech do not regularly cut corners like others (after all they are Flir). And the fact they could certify SMD tweezers to CatIII which I don't think they should have. So they discontinued it.

Let alone joeqsmiths experiments correlate the quality of the instrument with its labelling. Even for brands considered good quality.

My guess would be that the main objective for manufacturers with Cat ratings (in a beginners POV) would be legal liability. If a product is rated and can be shown to be falsely rated opens the manufacturer up for liability.

But even in the case of the Extech: 1. It did blow up but did not hurt Dave - it contained the blast; 2. Flir pulled it from the market upon learning of the design flaw; It would be hard to prove they designed the flaw on purpose...

But the flip side of this is that if the beginner used an independently verified DMM like a Fluke 87 - good luck suing Danaher (Fluke's Parent Company). Many standards are legal tools used to avoid liability (e.g. car safety standards).

Juxtapose the Gossen which is printed Cat II/ Cat III because it was made before the Cat IV specs were finalized. The exact same meter is Cat III/ Cat IV a mere 2 years down the line. And no - it isn't a series or a S/N away. Metrawatt consider them as Cat III/Cat IV devices and took down the Cat II/ Cat III specs. The inside seems to be the same. So YMMV if you look at the printed text.

BTW - There are ultimately better solutions for high energy circuits. Stuff like a Fluke T5 (That has no jacks or other exposed surfaces and real tough probes) - or voltage sensors that are mounted on extension poles. 

[Lightages]

WTF is that rambling stream of conscious rambling. What are you trying to say?

[Assafl]

WTF is that rambling stream of conscious rambling. What are you trying to say?

That evidence seems to suggest that the hypothesis that the IEC61010 ratings on DMMs reflect quality or safety is inconsistent at best.

It does not necessarily reflect on the quality or the safety of the meters. It may for some - but not for others.

So why would a beginner be told to depend on something that even we view with suspicion (until tested or verified)?

[vk6zgo]

WTF is that rambling stream of conscious rambling. What are you trying to say?

To quote Uncle Martin "You are a very redundant young man, young man!"

[Z80]

Some good points raised and it all applies to pros as much as hobbyists, but I exclude pros because they should already be aware of the hazards and don't need me or anyone else to teach them to suck eggs.  I totally agree that CAT ratings are just a certificate of compliance to a standard and not an indication of suitability for any particular scenario, that is an important distinction.  Taking the title of this thread, I would reverse the order and say that 'Why safe practices are so important and cat ratings', that's the message I'm trying to convey.  For example there is often mention of the 'annoying' insulation socks going down to the probe tip, well I unfortunately have had first hand experience of a colleague who had a bad habit of resting his fingers on the probes when measuring.  Not a problem 99% of the time but the occasion he went to measure a live transformer primary was a different story and I had to kill the power before it killed him.  He was 'live working' certified, but that training didn't mention not touching the probes, maybe it was too obvious.  There are many other examples like this I can quote.  There is unfortunately a lot of snobbery and almost evangelistic rantings here sometimes when it comes to test gear and particularly dmms.  This forum has a lot of respect associated with it so it would be easy for the uninitiated to believe it literally.  I have a lot of respect for mains electricity and everyone else should have to, but there is a gaping chasm between what you get in your home and what you get in a factory and the two should not be confused.

[b_force]

High CAT rated probes can only have a 4mm exposed tip, so it it surprises me a little.
Nevertheless, it's a good example that there is much more involved and what happens when people don't think.
I also have seen people using fully exposed tips, because they lost the isolation sleeves of the probes for example, or are to "lazy" to find them.
The lazyness factor is pretty common in a lot of accidents

[MrW0lf]

Around here you are subject to physical insight into physics of car accidents, when doing drivers license:
https://klimbergak.ee/wp-content/uploads/2017/01/kokkuporkesimulaator.jpg
https://klimbergak.ee/wp-content/uploads/2017/01/ymberp88ratav_auto.jpg
It would be utterly pointless to explain to people that their laptop might kill them in case of collision (due to massive inertia), let alone passenger w/o safety belt.
Cant help to see some parallels here.
Possibly need to buzz some sensitive body part at EE training until smoke comes out?
Only lone madmen have concept of safety w/o living thru some painful example.

[vk6zgo]

For decades, most test probes supplied with multimeters did not have the "insulation socks", & somehow, people measured voltages of the order of several hundreds of volts, both ac & dc.
(AVO extended the insulation down the probe for years, but were an exception).

Voltages of that order were the norm in earlier years, so people learnt to be careful.

It's not rocket science, for Pete's sake!

My first project at around 14 was a "one valve radio".
This used a 1T4 tube in a regenerative circuit, powered by a 1.5volt "D" cell for the filament, & , eeek!,
a massive 45volts HT.(from a battery)

It didn't work properly, (in retrospect, I think I connected the feedback winding backwards).

My next project was Mains operated------Horrors!

I believe that the general public was better informed of the dangers of Mains Electricity in those days, so that "beginners" were not as clueless as today.

[vk6zgo]

Around here you are subject to physical insight into physics of car accidents, when doing drivers license:
https://klimbergak.ee/wp-content/uploads/2017/01/kokkuporkesimulaator.jpg
https://klimbergak.ee/wp-content/uploads/2017/01/ymberp88ratav_auto.jpg
It would be utterly pointless to explain to people that their laptop might kill them in case of collision (due to massive inertia), let alone passenger w/o safety belt.
Cant help to see some parallels here.
Possibly need to buzz some sensitive body part at EE training until smoke comes out?
Only lone madmen have concept of safety w/o living thru some painful example.

That never used to be the case.
People had sufficient general knowledge  to understand things without  simulations & suchlike  crap.
A classic case is that of phase--- hundreds of students learnt about this & formed mental images  without the slightest difficulty.
The standard now seems to be that students absolutely have to have simulations, or set a display up on a
'scope.

It seems that imagination is no longer original equipment with humans.

[MrW0lf]

It seems that imagination is no longer original equipment with humans.

Who needs imagination when you have media shaping picture for you. Constantly being fed concept of higher than actual chance of survival when something goes wrong. Just have fun, I'll all work out just fine

[Mr. Scram]

Back in the day, we didn't even have isolation on our wires and we liked it that way!

[b_force]

aaah, yes, back in the day.
You know what?
Back in the day, back in the day was everything better as well.
And back in the day, back in the day, also back in the day was everything better.

Maybe we should go back living in caves again