Why CAT ratings are so important AND safe practises - Page 1
Forum section: electronics / testgear

author: TheNewLab
author_rank: Frequent Contributor
timestamp: December 07, 2016, 09:18:07 am
content: Hi I found this you tube video that i happened across that made me think of all the CAT ratings dialogue and Dave's discussion on itHere is the Link:

author: Assafl
author_rank: Frequent Contributor
timestamp: September 18, 2017, 04:50:24 am
content: 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.

author: Assafl
author_rank: Frequent Contributor
timestamp: September 18, 2017, 05:49:38 am
content: Quote from: blueskull on September 18, 2017, 05:03:58 amThere are indeed electricians that did not have the mindset to be one.There are also those that did 20 years in domestic installations and based on their certification were given employment at an industrial installation or utility (and needing a job did not approach their boss and admit to being terrified).And then there are the really good, careful ones, that one time (too many) were in a hurry to get home (kids birthday, anniversary, etc.).They are all dead... (with IEC60900 pliers and IEC61010 Cat IV rated Flukes spread around them).

author: Jeroen3
author_rank: Super Contributor
timestamp: September 18, 2017, 06:55:18 am
content: I often work around generators, floating my hands around 400V busbars. Because that is where the equipment is.Fooling around with not-enough AWG cabling and on-the-edge breakers. No problem.Please note: generators have a limited short circuit capability. Yet, enough to melt your banana leads in a seconds.However I do not touch or open grid side switchgear. The grid has aninfiniteshort circuit capability.

author: Lightages
author_rank: Unknown
timestamp: September 18, 2017, 07:36:32 am
content: CAT ratings are not safety.User experience is not safety.Being an idiot at any moment can end in tears.Being careful, diligent, and follow training can save your life.What do I mean by all of these statements? People make mistakes and safety ratings and procedures have been implemented to save you from your human stupidity. Follow check lists, procedures, and using proper equipment will reduce your risk to serious injury quite a bit. Unfortunately, making something idiot proof just produces better idiots. Sometimes luck just grabs you and you become the reason that safety standards get revised.In the home, CATIII/300V is enough for equipment. The examples posted in this thread so far are outside of the hobbyist's domain. If you are poking things into the kinds of systems that have been demonstrated in this thread, then you have no business doing so unless you are a high voltage industrial electrician. This has nothing to do with home electronics or home electricity.These images and videos illustrate the extremes of what can happen and perhaps provide caution. People should not just do something without thinking about the possible consequences.That being said, hobbyists need to understand CAT ratings. IMHO, if you don't understand CAT ratings, no hobbyist should buy a multimeter with less than a CATIII 300V unless they now why they don't need to. Full stop, opinion stated.

author: Electro Detective
author_rank: Super Contributor
timestamp: September 18, 2017, 09:28:58 am
content: Quote from: Assafl on September 18, 2017, 05:49:38 amThey are all dead because it was"only a job..."= wrong deadly attitudeHad they taken a keen interest learning and understanding the power systems they worked on, qualified or not,and been of a suspicious nature to not trust or assume anything,they would be with their families and friends now and surfing EEVblog forum and Youtubeinstead of buried fried maggot fodder

author: nctnico
author_rank: Super Contributor
timestamp: September 18, 2017, 10:09:32 am
content: Quote from: Assafl on September 18, 2017, 04:50:24 amWell, you can't fix stupid. He clearly used the wrong tool for the job. CAT rated doesn't meanindestructiblebuttested to certain limits. When working on 2000V you need equipment (CAT) rated for at least 2000V.

author: Fungus
author_rank: Super Contributor
timestamp: September 18, 2017, 10:57:00 am
content: There's other factors, too.If you have kids at home, would you want them to copy dad and connect a DT830B up to a mains socket and turn the dial?Quote from: Assafl on September 18, 2017, 04:50:24 amI always tell people about the $42 (delivered) Fluke 101. That's not expensive.I think the Fluke 87V is complete overkill for just about everything. $15 meters work fine for low voltage stuff, the 101 is great for household mains. Buy both and you can handle anything except industrial AC power for under $50.Get an 87V if your job requires one, otherwise it's a luxury item. I'd never tell a newbie to buy one.

author: CopperCone
author_rank: Super Contributor
timestamp: September 18, 2017, 11:09:19 am
content: just give er a real quick tap with your hands

author: b_force
author_rank: Super Contributor
timestamp: September 18, 2017, 03:55:25 pm
content: A re-post of a re-port of a re-port?So here we go again (and again, and again, and again)You know the fun part about safety rules?They are totally different in other countries.So I guess 'what is considered being safe' is even very subjective

author: Fungus
author_rank: Super Contributor
timestamp: September 18, 2017, 03:59:01 pm
content: Quote from: b_force on September 18, 2017, 03:55:25 pmCAT ratings are international.

author: nctnico
author_rank: Super Contributor
timestamp: September 18, 2017, 04:12:53 pm
content: Quote from: b_force on September 18, 2017, 03:55:25 pmWrong conclusion. Safety rules are usually very similar but can be different due to circumstances in a specific country. For example: there is no use for laws&regulations regarding winter tires if it never snows/freezes in a country.

author: b_force
author_rank: Super Contributor
timestamp: September 18, 2017, 04:17:07 pm
content: Quote from: Fungus on September 18, 2017, 03:59:01 pmExcept chinaThis topic is about CAT ratings & safe practices.A CAT rating is part of something, but definitely NOT equal to safety.Like other people already mentioned in this post.I was referring to safety rules in general, which are (apparently) pretty subjective.QuoteOn this whole never ending (so it seems) debate.This is the only proper response I have ever read!Most people won't even go any further than CATII or even CAT I .A smart person always works with a (properly fused) isolation transformer(That way you will always work in CAT I conditions)

author: b_force
author_rank: Super Contributor
timestamp: September 18, 2017, 04:21:29 pm
content: Quote from: nctnico on September 18, 2017, 04:12:53 pmThat definitely not a wrong conclusion.You're now talking about a very specific case.Obviously, I am talking about general stuff, so lets say wiring and how the fuse board/distribution board is being made.Also things like grounding/earth switch.Just compare what's being done and considered 'safe' in USA, AUS/NZ, NL, B (belgium), GER, UK and Spain for example (fill the list with more)It's like a comedy show. Things that are even a standard procedure in one country, are absolutely a no go in others.Anyway, the point are not the details, but the fact that there are significant differences.

author: Unknown
author_rank: Unknown
timestamp: September 19, 2017, 11:07:19 am
content: As this is an electronics forum, CAT ratings are irrelevant. Electronics is CAT I a mains socket is CAT II. If you need a CAT III or CAT IV meter, you are no longer an electronics hobbyist.

author: Fungus
author_rank: Super Contributor
timestamp: September 19, 2017, 12:32:43 pm
content: Quote from: Z80 on September 19, 2017, 11:07:19 amElectronics hobbyists don't build huge power supplies or Tesla Coils in their sheds??

author: Unknown
author_rank: Unknown
timestamp: September 19, 2017, 01:24:28 pm
content: Quote from: Fungus on September 19, 2017, 12:32:43 pmNo they don't. I know what you are trying to do but huge supplies & Tesla coils are not typical hobby projects. If you build such things then you better know what you are doing

author: Fungus
author_rank: Super Contributor
timestamp: September 19, 2017, 02:11:25 pm
content: Quote from: Z80 on September 19, 2017, 01:24:28 pmYou must be new here.OK, they're not "Instructibles-level" projects, but you're not on Instructibles, you're on EEVBLOG.And... people who don't know what they're doing have all the more reason to get a real CAT-rated meter.

author: b_force
author_rank: Super Contributor
timestamp: September 19, 2017, 02:23:47 pm
content: Quote from: Fungus on September 19, 2017, 02:11:25 pmThat's actually the wrong piece of advice.People don't know what they are doing shouldn't even touch electronics, period.Or only the very low voltage stuff (arduino 3V, 5V & 12V tops so to speak)This is a typical example that an higher rating meter is actually going to do more harm than good.Because untrained people think they are safe because of that rating.Simple psychology how peoples minds work."It's all safe because the equipment said it was rated for it".Exactly the reason why people advocate against strict rules, but that people should use their brains.If they don't (wanna) use their brains, just stay far away from it, don't even buy a meter!

author: Unknown
author_rank: Unknown
timestamp: September 19, 2017, 02:27:04 pm
content: Quote from: Fungus on September 19, 2017, 02:11:25 pmI see, you are one of those people. Ok, you say we are on EEVBLOG so perhaps you want to list Dave's videos where he builds or reviews huge stuff and Tesla coils? No? If you really feel strongly then you should contact UL and tell them electronics should not be listed as CAT I because clearly they don't know what they are talking about.

author: Fungus
author_rank: Super Contributor
timestamp: September 19, 2017, 02:44:00 pm
content: Quote from: Z80 on September 19, 2017, 02:27:04 pmDave doesn't, the forum members do.Show me a single one of Dave's multimeter teardowns where he doesn't talk about CAT ratings.Look at his latest one - the Sanwa pocket meter. He goes into detail of the CAT rating and specifically says he doesn't want current measurement. He's said many times he doesn't want current ranges on meters that might be poked into a mains socket.Quote from: Z80 on September 19, 2017, 02:27:04 pmMe?You'rethe one trying to fit the word "hobbyist" into a tiny little box.By any dictionary definition I'm only a hobbyist - nothing in my job description or CV has anything to do with electronics. Yes, I've built Tesla Coils.

author: Cerebus
author_rank: Super Contributor
timestamp: September 19, 2017, 04:09:54 pm
content: Quote from: Z80 on September 19, 2017, 11:07:19 amYes, this is an electronics forum. It is not exclusively ahobbyelectronics forum. There are a lot of professionals on here, some with someseriouspower systems chops. Even if it was purely hobbyist, just becauseyourhobby ends at 5V and 40 mA don't assume everybody else's does.

author: Assafl
author_rank: Frequent Contributor
timestamp: September 19, 2017, 04:36:45 pm
content: Huge power supplies above 240v/125kVA (the 125kVA exception) where an arc flash analysis must be made? That is more than a domestic feed of 3~ 230v 60A. Let alone an apartment.Or smaller than that.CAT ratings 3 and above are about Arc Flash sort of energies. The voltage rating is about the insulation.One can only hope those in Industry above the exception know that indeed they are in mortal danger. Whereas those at home avoid the utility feed and the fuse box.

author: Unknown
author_rank: Unknown
timestamp: September 19, 2017, 05:34:15 pm
content: Yes of course I am aware there are professionals hereand they already know what they are doing and are not the target of this discussion. If you are a responsible adult and have the money to spare then buy whatever makes you happy, no issue with that. I'm also well aware that Dave has a strong opinion on CAT and that is usually directed towards if they are likely to be real or fake. Everyone is fully entitled to their view. My view is this: For electronics (and since this is a point of contention) I will define it as CAT I and CAT II only, ie low voltage circuit boards and domestic mains outlets. If you want to play with big capacitor banks that is outside the scope and falls in the 'you know what you are doing' category.Buying a meter because it has a CAT IV rating is nonsense. There are more important criteria like accuracy, features, does it have max hold, a good continuity tester low current ranges, burden voltage, capacitor test etc. High energy safety is low on my list because I won't ever need it. It also irks me when beginners are directed towards expensive industrial meters for several reasons, notably: It gives a false sense of security and can lead to "I'm not sure if I should do this but..." moments. Secondly, many moons ago when I was knee high to a grasshopper popping a 300mA fuse was a common occurence. Not a problem, glass fuses (240V certified) are ten a penny and perfectly safe for low energy electronics and the mains. I worry sometimes that a youngster could have a meter with expensive HRC fuses and being skint, cheap out and buy fake crap of Fleabay or just wrap a bit of wire round the lugs. After getting bored and moving on to the next hobby, the meter ends up being sold and used in a real CAT III / CAT IV situation and that may not end well.

author: Lightages
author_rank: Unknown
timestamp: September 19, 2017, 06:58:20 pm
content: There is also another point about CAT ratings here. They are important, but what is also important is how to know when the CAT rating is real on a meter and is not just a lie to sell more meters. This is probably why Dave always does an inspection of a meter to see if it is possible it could actually meet its rating. It can be obvious when it can't possibly meet the claim. It is not see easy to see if it actually does.False CAT ratings are worse than none at all. A person might trust a meter to meet its CAT rating and have some big problems, kill the meter, or kill the DUT. A good example is the Uni-Trend UT61E. It was originally rated at CATIV 600V and CATIII 1000V. It is still sold this way world wide. It is a lie and could never meet these claims. The fuses are incorrect for this. There are other design considerations that don't meet the claims. There is a European version with GS certification. The fuses and input protection have been upgraded considerably but it is only rated at CATIII 300V and CATII 600V! In other words the falsely labelled one might fool someone into using it on the distribution panel when it appears it couldn't even be safe to use in a wall socket in a house.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.

author: Assafl
author_rank: Frequent Contributor
timestamp: September 19, 2017, 08:40:55 pm
content: Quote from: Lightages on September 19, 2017, 06:58:20 pmDisagree 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".

author: Lightages
author_rank: Unknown
timestamp: September 19, 2017, 08:45:13 pm
content: Huh? What did say? Oh let me repeat myself: "Education is more important".

author: Assafl
author_rank: Frequent Contributor
timestamp: September 19, 2017, 08:52:46 pm
content: Quote from: Lightages on September 19, 2017, 08:45:13 pmHuh? What did say? Oh let me repeat thyself: "Education is more importantbut 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.

author: Lightages
author_rank: Unknown
timestamp: September 19, 2017, 09:04:00 pm
content: 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.

author: b_force
author_rank: Super Contributor
timestamp: September 19, 2017, 09:24:22 pm
content: 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

author: Assafl
author_rank: Frequent Contributor
timestamp: September 19, 2017, 10:44:12 pm
content: Quote from: b_force on September 19, 2017, 09:24:22 pmThere 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.

author: joeqsmith
author_rank: Super Contributor
timestamp: September 19, 2017, 11:00:25 pm
content: 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.

author: nctnico
author_rank: Super Contributor
timestamp: September 19, 2017, 11:02:46 pm
content: 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'.

author: Mr. Scram
author_rank: Super Contributor
timestamp: September 19, 2017, 11:59:54 pm
content: Quote from: Assafl on September 18, 2017, 04:50:24 amWhy 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.

author: Mr. Scram
author_rank: Super Contributor
timestamp: September 20, 2017, 12:02:17 am
content: Quote from: nctnico on September 19, 2017, 11:02:46 pmThe 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.

author: b_force
author_rank: Super Contributor
timestamp: September 20, 2017, 12:32:39 am
content: Quote from: Mr. Scram on September 20, 2017, 12:02:17 amAnd 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.

author: Mr. Scram
author_rank: Super Contributor
timestamp: September 20, 2017, 01:07:46 am
content: Quote from: b_force on September 20, 2017, 12:32:39 amIt'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.

author: Lightages
author_rank: Unknown
timestamp: September 20, 2017, 05:24:42 am
content: 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.pdfSo 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.

author: Assafl
author_rank: Frequent Contributor
timestamp: September 20, 2017, 06:04:21 am
content: 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.

author: Lightages
author_rank: Unknown
timestamp: September 20, 2017, 06:10:56 am
content: WTF is that rambling stream of conscious rambling. What are you trying to say?

author: Assafl
author_rank: Frequent Contributor
timestamp: September 20, 2017, 07:00:15 am
content: Quote from: Lightages on September 20, 2017, 06:10:56 amThat 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)?

author: vk6zgo
author_rank: Super Contributor
timestamp: September 20, 2017, 08:35:14 am
content: Quote from: Lightages on September 20, 2017, 06:10:56 amTo quote Uncle Martin "You are a very redundant young man, young man!"

author: Unknown
author_rank: Unknown
timestamp: September 20, 2017, 09:06:38 am
content: 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.

author: b_force
author_rank: Super Contributor
timestamp: September 20, 2017, 09:46:00 am
content: 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

author: MrW0lf
author_rank: Frequent Contributor
timestamp: September 20, 2017, 10:07:54 am
content: 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.jpghttps://klimbergak.ee/wp-content/uploads/2017/01/ymberp88ratav_auto.jpgIt would be utterly pointless toexplainto 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.

author: vk6zgo
author_rank: Super Contributor
timestamp: September 20, 2017, 10:34:50 am
content: 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.

author: vk6zgo
author_rank: Super Contributor
timestamp: September 20, 2017, 11:51:33 am
content: Quote from: MrW0lf on September 20, 2017, 10:07:54 amThat 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.

author: MrW0lf
author_rank: Frequent Contributor
timestamp: September 20, 2017, 12:06:40 pm
content: Quote from: vk6zgo on September 20, 2017, 11:51:33 amWho 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

author: Mr. Scram
author_rank: Super Contributor
timestamp: September 20, 2017, 12:29:04 pm
content: Back in the day, we didn't even have isolation on our wires and we liked it that way!

author: b_force
author_rank: Super Contributor
timestamp: September 20, 2017, 01:10:43 pm
content: 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

author: HoracioDos
author_rank: Frequent Contributor
timestamp: September 20, 2017, 02:17:46 pm
content: I agree that CAT ratings are a guidance and education is a key. Customers (skilled and unskilled) should be more aware of it, like fat, sugar or calories in the food. Many things have changed since people is concerned about nutrition facts.We should ask manufacturers to stop lying about CAT ratings if we know for sure that their products are not in compliance.

author: Cerebus
author_rank: Super Contributor
timestamp: September 20, 2017, 02:49:40 pm
content: Quote from: b_force on September 20, 2017, 01:10:43 pmI thought that some of you antipodeansdid!

author: b_force
author_rank: Super Contributor
timestamp: September 20, 2017, 02:56:00 pm
content: Quote from: HoracioDos on September 20, 2017, 02:17:46 pmThan you also should stop asking the costumers to go for the lowest price and/or step away from the whole idea of making as much profit as possible.I guess the only thing you can do, is form some laws and regulations about it, but there are so many grey areas.Plus you don't want to much resistance in innovation.In the end it's a compromise, companies/countries need more 'technical skilled' people because the amount of work.So somehow they need to make a compromise between how difficult it is to get these skills and to fill all the vacancies.

author: b_force
author_rank: Super Contributor
timestamp: September 20, 2017, 02:57:01 pm
content: Quote from: Cerebus on September 20, 2017, 02:49:40 pmWell, according to the pictures they still use electricity, so.. alas.

author: Fungus
author_rank: Super Contributor
timestamp: September 20, 2017, 03:23:42 pm
content: Quote from: b_force on September 20, 2017, 12:32:39 amI've got a CAT III area inside my house. CAT IV if I snip a little wire that has a lump of lead squished onto it for 'safety' (as if that little wire would stop anybody, LOL!)

author: HoracioDos
author_rank: Frequent Contributor
timestamp: September 20, 2017, 06:17:07 pm
content: I understand your point but I look the whole thing in a different way.Quote from: b_force on September 20, 2017, 02:56:00 pmI think that's not the problem. Best decisions are usually made when we are well informedQuote from: b_force on September 20, 2017, 02:56:00 pmI don't trust governments for anything good, I don't like to feed bureaucracy monster. I guess that civil organizations could make their own statement to alert customers to avoid some products. It seems that mislabelled DMMs is not an issue for them.Quote from: b_force on September 20, 2017, 02:56:00 pmIf any company can't find good engineer to design a multimeter, they are in the wrong business in any market. It's a bad policy in long term for any company or country to allow these product get exported with wrong CAT ratings.

author: oldway
author_rank: Super Contributor
timestamp: September 20, 2017, 07:43:18 pm
content: If I understand correctly, the electrician tried to make a measurement with a multimeter on a high energy circuit of 2300V.It could only end badly.Which would have only caused damage to the multimeter in the case of a low-energy circuit, becomes a fatal accident with a high-energy circuit.This is not just a CAT problem.In the video, we have very well made a list of all the errors and breaches of the safety rules.which have been committed and there are many!An accident rarely has a single cause ... it is proved once again !.

author: mtdoc
author_rank: Super Contributor
timestamp: September 20, 2017, 08:04:23 pm
content: Quote from: blueskull on September 18, 2017, 05:03:58 amThis statement and this whole discussion reminds me a lot of similar discussions that take place in the climbing community.A common saying is "There are old climbers and there are bold climbers but there are no old, bold climbers".The issue in both settings are the same: Safety rules are important but they are not alone sufficient. There are many instances in climbing where blindly following the safety rules can give one a false sense of security and in some cases actually put you in mortal danger. I believe the same thing is true if working in high power electrical environments.Understanding the underlying principles, situational awareness and exercising good judgement are the most important thing.

author: b_force
author_rank: Super Contributor
timestamp: September 20, 2017, 08:15:19 pm
content: Quote from: HoracioDos on September 20, 2017, 06:17:07 pmTo be clear, I m not saying that I agree with all these things either.I am just trying to give a general explanation, why and how things work.Also, I wasn't talking about one company that isn't able to find workers.I was explaining when a lot of companies have a shortage in workers, that's becoming a national or even an international problem.Of course it's not in their policy that's allowed to make bad products.But rather a result of a compromise they made.Anyway, the point is that these work much more complex and are very far from black & white.

author: RGB255_0_0
author_rank: Frequent Contributor
timestamp: September 20, 2017, 08:55:23 pm
content: Quote from: oldway on September 20, 2017, 07:43:18 pmAnd then you see his colleague walking around with a metal chain down by his trousers.

author: HoracioDos
author_rank: Frequent Contributor
timestamp: September 20, 2017, 09:06:11 pm
content: Quote from: mtdoc on September 20, 2017, 08:04:23 pmPaul Petzoldt

author: Lightages
author_rank: Unknown
timestamp: September 20, 2017, 11:36:21 pm
content: Quote from: vk6zgo on September 20, 2017, 08:35:14 amYeah, I goofed up on some wording. Thank you for being such a word nazi.

author: Unknown
author_rank: Unknown
timestamp: September 21, 2017, 02:15:14 pm
content: You have to wonder why the cheapo companies bother with the fake markings, possibly because they are just copying the big brands and want them to look the same. I would hate to think that they are driven to do this by the consumer market wanting them as some sign of 'status' or thinking they are better, like the fake mAH ratings on battery banks or the ridiculous wattages on cheap 'hifi'. The fact remains that the consumer / hobby market doesn't need them, that's why your toaster / TV / fridge doesn't have them.

author: Fungus
author_rank: Super Contributor
timestamp: September 21, 2017, 02:39:36 pm
content: Quote from: Z80 on September 21, 2017, 02:15:14 pmWhat other reason could there possibly be?

author: b_force
author_rank: Super Contributor
timestamp: September 21, 2017, 02:53:13 pm
content: It's pretty simple. Because there is a market for and people are willing to pay some money for it.Their development costs are close to zero.And ones again, there are A LOT of people who don't know anything about CAT ratings.In fact, most professional electronics engineers I speak don't know much about it.It's only electricians who need to know something about it because they have to deal with it on a daily basis.So they simply see a label, and think it's a proper product.That's how marketing works.Maybe this is obvious for you (and us) that these meters are very doubtful in quality.Keep in mind that in some countries there are no strict rules and regulations.So from that point of view you can't blame the manufacturer, simply because he probably doesn't know any better.All his friends, family etc are also exporting cheap stuff, so why can't he do it?Keep in mind that Chinese business culture is a little different.From an engineering and cost price perspective I find it very interesting.Joe Smith showed it's not THAT hard to make a very good performing front end.So in a sense it would be possible to make a very good performing multimeter for just 25-30 bucks.

author: Fungus
author_rank: Super Contributor
timestamp: September 21, 2017, 03:05:26 pm
content: Quote from: b_force on September 21, 2017, 02:53:13 pmJoe never tests any meter on the current ranges.You'd need properly rated fuses for the current ranges and that could add $15 to the meter all by itself.(although I'm still not sure why those fuses cost so much)

author: b_force
author_rank: Super Contributor
timestamp: September 21, 2017, 03:12:56 pm
content: Quote from: Fungus on September 21, 2017, 03:05:26 pmThat's also part of your answer.Just because companies can.

author: Cerebus
author_rank: Super Contributor
timestamp: September 21, 2017, 04:12:58 pm
content: Quote from: b_force on September 21, 2017, 03:12:56 pmIt's also a question of demand. There are two companies (Bussman, Littelfuse) making fuses that fit the majority of the Fluke handhelds. The 11A fuse has a 20kA interrupting rating at 1000V DC and the 440mA a 10kA rating at 1000V DC, that's quite a tall order for a physically small fuse.By comparison, the household BS1362 13A fuse has an interrupting rating of 6 kA at 250V AC. These are made by every man and his dog and only cost around the £0.13 mark if bought from Bussman.A similar rated 20x5mm F 12.5A 250V HRC fuse comes in at around £1.50 for a very similar capability to the aforementioned BS1362 13A.So, the price factor for 'specialized' 20x5mm versus 'every household' BS1362 is about 111/2.It's plainly obvious that the material costs of a fuse are going to go hand in hand with the power it's rated to break, so the 440mA 'Fluke' fuse should cost around 6.7 times what the 20 x 5mm fuse does. And indeed, £1.50 is something close to the price of a 'Fluke' fuse divided by that 6.7 factor.So there's two factors.Middling demand fuses, such as multimeter fuses and high current 20x5mm HRC are always going to cost more than high demand items like BS1362 fuses which in fact are a bargain for their rated breaking capacity.Interrupting capacities of 10kA and 20 kA at 1000V DC are just going to be expensive to implement.

author: Fungus
author_rank: Super Contributor
timestamp: September 21, 2017, 05:50:12 pm
content: Quote from: Cerebus on September 21, 2017, 04:12:58 pmIt's mostly (all?) just a case of making them bigger. There's no fancy materials inside them, just sand+wire.It's been suggested that the problem is very tight tolerances in the timing of the way they blow but I find that hard to believe. We consume high-precision parts in every area of our lives for cents apiece. eg. The opening mechanism on soda cans.My only conclusion is they're overpriced just to reassure us that they're good.That doesn't explain why the Chinese don't make them for only double/triple the price of BS1362 fuses though.

author: b_force
author_rank: Super Contributor
timestamp: September 21, 2017, 05:55:38 pm
content: Be aware that quality isn't proportional to price.I know some audio companies who sell the same boards for OEM and consumers.Only the consumer prices are 6 timers higher.The BOM is almost identical.I have also seen other companies where I know the exact BOM (and therefore the production price).They sell their stuff for a much much higher rate.It's worse with companies that almost have a monopoly.

author: Cerebus
author_rank: Super Contributor
timestamp: September 21, 2017, 06:06:03 pm
content: Quote from: Fungus on September 21, 2017, 05:50:12 pmThe external construction of the 'Fluke' fuses is quite different to normal industrial HRC fuses of the same physical size (some sort of glass/kevlar reinforced plastic versus ceramics), and their breaking capacity per unit volume is a bit higher than standard industrial fuses. They have to be made more physically robust because they are expected to blow in hand held equipment, not behind the steel door of some switchgear. I wouldn't however expect this to contribute too much to the cost (cost as opposed to price), maybe a factor of two at most.But that's not the point, the point is the demand for them and the number of manufacturers versus more everyday fuses. It's economics, not technology.

author: Cerebus
author_rank: Super Contributor
timestamp: September 21, 2017, 06:14:55 pm
content: Quote from: b_force on September 21, 2017, 05:55:38 pmIt's got nothing to do with quality (beyond basic product requirements), it's quantity - a market of 10s of thousands versus markets of millions and two manufacturers versus dozens.. An economist would discuss it in terms like 'economies of scale', 'price sensitivity of demand', 'duopoly', 'market entry costs' and 'effective competition'.

author: madires
author_rank: Super Contributor
timestamp: September 21, 2017, 06:23:03 pm
content: You can get HRC fuses for DMMs also from ESKA and SIBA for a reasonable price.

author: b_force
author_rank: Super Contributor
timestamp: September 21, 2017, 07:36:12 pm
content: Quote from: Cerebus on September 21, 2017, 06:14:55 pmI can guarantee it's also not always quantity.Some manufactures just really ask bizarre prices.

author: Fungus
author_rank: Super Contributor
timestamp: September 21, 2017, 07:47:58 pm
content: Quote from: Cerebus on September 21, 2017, 06:14:55 pmNah. If they were cheaper then you'd see them in a lot more meters.

author: joeqsmith
author_rank: Super Contributor
timestamp: September 22, 2017, 01:39:58 am
content: Quote from: Fungus on September 21, 2017, 03:05:26 pmFrom a safety standpoint, nothing I have shown could be considered an improvement. The changes would need to be put to the test. That's not free. If you only sold one meter ever, that would be a lot more than $30 to recover your testing costs. Start adding zero's behind it.. lol.I showed a highly modified UNI-T UT61E where I attempted to lower the burden voltage and increase the current it could handle. I did a fair amount of testing with it but not for safety.

author: Lightages
author_rank: Unknown
timestamp: September 22, 2017, 05:05:32 am
content: The is not exactly on topic, but very relevant:

author: vk6zgo
author_rank: Super Contributor
timestamp: September 22, 2017, 05:11:54 am
content: Quote from: Lightages on September 20, 2017, 11:36:21 pmNah! I'm only a "word Neo Con" at worst.A real word nazi would have pointed out that you wrote "conscious" where you meant " consciousness".

author: vk6zgo
author_rank: Super Contributor
timestamp: September 22, 2017, 05:23:35 am
content: Quote from: Cerebus on September 21, 2017, 06:14:55 pmAnother point is that historically, instrument manufacturers dealt mainly with businesses who bought them for use by employees.To very large organisations, such as equipment manufacturers, Communications & Broadcasting companies, & the Military, the price of a few fuses, or indeed, a few multimeters would be lost in their other operating costs.The large scale ownership by individuals of DMMs of a fair degree of sophistication is only a quite recent phenomenon, & the manufacturers are just continuing with their time honoured pricing structure.

author: Unknown
author_rank: Unknown
timestamp: September 22, 2017, 09:14:27 am
content: Quote from: blueskull on September 22, 2017, 04:09:31 amYes absolutely, a little knowledge can be a dangerous thing. The biggest dangers from your home electrics are shock and fire, HRC won't help you with those. Even in the industrial world, arc flash / blast are fortunately quite rare because only trained professionals with the correct paperwork & permits are given the keys to the big stuff. I looked at the UK RIDDOR stats (this is an official govt accident report system) and the biggest source of injury or death amongst electricians by a country mile is falling / tripping, arc flash doesn't even get a mention.

author: HoracioDos
author_rank: Frequent Contributor
timestamp: September 22, 2017, 12:11:21 pm
content: Quote from: blueskull on September 22, 2017, 04:09:31 amGood to know! Here we say: Confidence kills a man and makes a woman to get pregnant

author: madires
author_rank: Super Contributor
timestamp: September 22, 2017, 01:52:35 pm
content: Quote from: Z80 on September 22, 2017, 09:14:27 amWe call those people "experts with dangerous half-knowledge"Quote from: Z80 on September 22, 2017, 09:14:27 amOver here a DMM with proper HRC fuses should be fine for home electrics because the main fuses are commonly 35A. They are located in a dedicated sealed box and may only be accessed by the electricity supplier or a licensed sparky. Anyway, I would use something like a Duspol for checking mains and a clamp meter for current measurements. In typical cases a DMM is simply the wrong tool for mains. And someone poking around in industrial environments should have a sound education for that kind of work.

author: Assafl
author_rank: Frequent Contributor
timestamp: September 22, 2017, 01:56:04 pm
content: BTW - using a fake rating DMM or a non rated DMM (albeit I think ALL have maximum voltage - even the old ones - no?) is the same as using gadgets "made in china" (crap gadgets - not the good stuff).What about laptop bricks that have very little isolation (especially going to a nice metal case laptop)?Some are worse like the water heater that just uses electrodes of 220v into a cup?All of these can kill a beginner in much the same way a bad DMM can.

author: Fungus
author_rank: Super Contributor
timestamp: September 22, 2017, 02:39:39 pm
content: Quote from: Assafl on September 22, 2017, 01:56:04 pmTwo wrongs don't make a right.

author: b_force
author_rank: Super Contributor
timestamp: September 22, 2017, 02:58:30 pm
content: Quote from: Assafl on September 22, 2017, 01:56:04 pmOfficially older multimeters can be considered as a 'non-rated multimeter'.Most meters produced before 1997 don't meet the standards.Like the original Fluke 70-series.Newer ones are mostly under-rated.Isolation and proper (earth) grounding is a whole different story.

author: Assafl
author_rank: Frequent Contributor
timestamp: September 22, 2017, 03:05:54 pm
content: Quote from: Fungus on September 22, 2017, 02:39:39 pmFor the obvious snide remark - yes they do. One shock stops the heart, and the defibrillator one gets it pumping again.Sorry - had to.That said the laptop is probably worse:1. It is in your lap. I have yet to stuff my DMM near my crotch once.2. It is used much more than the DMM - for most. Hence the exposure to the risk is much higher.3. Hopefully a DMM user can open his DMM and check the layout. In a brick - all you can do is trust china.4. The percentage of DMM users aware of the risks is higher than the rate of brick users who do.So bricks are substantially more dangerous. And like crap DMM makers, these also love fake or self certifications.I say we shame them all.

author: Electro Detective
author_rank: Super Contributor
timestamp: September 23, 2017, 09:16:11 am
content: Blah blah blah...Once the plastic screw posts crack in MOST Flukes and other meters, you can kiss the BANG! containment CAT ratings goodbyeOption 1:A couple of duct/duck tape layers on the sides of the meter 'MAY' keep it together during a BANG!/POP/POW!still a lot better than relying on tired flimsy cracked postsand deluded brand loyalty BSOption 2:Rather than rely on 'coin toss' CAT ratings from any meter manufacturer, join some religion that can reserve you a spot in their afterlife program,in case the hyped meter you are grasping goes nuke when performing a dumbass 'terminal' measurermentOption 3: (My personal choice)DO NOT TRUST ANY METER!Use what you have wisely, your family and friends have better things to do than visit your sad ass in hospital, rehab, or crematorium/ditch siteOption 4: Use FUSED LEADS, face shield, gloves, and dry wood holders for the leads,especially if the day hasn't gone well or some scumbag stupervisor boss clown barks like a rabid dogto hurry up and 'Just Do It!'(Option 4b: tell him or her to go **** themselves and stick the crappy job up their ***,or hand them the CAT meter, and DARE them to measure the risky **** themselves)Option 5: Stick to Arduino stuff and battery checkingOption 6: Come on...if the 5 options above weren't enoughthen don't buy a meter, and consider a hobby change to gardening or cooking instead

author: Fungus
author_rank: Super Contributor
timestamp: September 23, 2017, 12:16:25 pm
content: This thread is now(just like every other thread on this subject)If you want garanteed safety then don't ever go near electricity. Or drive a car. Or go outside the house.

author: Unknown
author_rank: Unknown
timestamp: September 23, 2017, 07:18:00 pm
content: Quote from: Fungus on September 23, 2017, 12:16:25 pmWell if it bores you so much then there are hundreds of other threads to go and troll in.

author: Lightages
author_rank: Unknown
timestamp: September 23, 2017, 08:35:56 pm
content: Another relevant thread....https://www.eevblog.com/forum/chat/my-first-dt830d-current-mode-spark/