What On Earth - Page 1
Forum section: electronics / general

author: PsychoMaster
author_rank: Regular Contributor
timestamp: February 27, 2015, 10:28:54 am
content: All this big faff about Chinese meters not having enough input protection to stop an elephant .How many of us ever go near big voltages? If you do then spend bigger bucks .It's not fair to expect it from people who create these things for a very low price is it? You know if you are going to deal with dangerous voltages by now .You get some guy testing these things and making a big deal about the ratings that,s printed on them,why don,t he just grow up I mean we know they would print 'Endorsed by Batman' if they thought it helped sales .We are supposed to be grown ups we know it,s not real and if you are that stupid then you shouldn’t be near electricity in the first place.I have had an old Gunson meter for twenty years , if you took it apart you would say it,s a piece of crap but it has got me out of trouble hundreds of times and it has earned me thousands .Never once have I been stupid enough to alter the settings while in circuit or stick into the mains .We are suppose to have a brain and think about the devices we are using and not letting any one else use your stuff if you can't trust them .I don't like to see Chinese products being looked down on when some of us would not have much of a hobby without them.

author: Howardlong
author_rank: Super Contributor
timestamp: February 27, 2015, 10:51:10 am
content: Although it is not de rigeur, I do tend to agree with you as a generalisation. Particularly for hobbyists, it would be extremely unlikely they'd be fiddling with 3-phase for example, but there are occasions, particularly in valve/tube high power applications like RF PAs, where you do need to take particular care, even a CAT IV isn't going to cut it, but if you're fiddling with that stuff you really do need to know what you're doing, a CAT IV multimeter won't save you from yourself in those circumstances.However that lack of attention to detail can sometimes be an indication of other problems, especially if the claimed CAT rating is unsupported by the physical design.There will however be professional reasons to go for a particular measurement category, often for indemnity reasons. My concern is that standards like these are all to often used as a box ticking exercise, without actually understanding that having a particular device with a CAT rating does not suddenly absolve you of responsibility for looking after yourself as well as those who may work for you, although it is part of a general psychology of good practice.It is like the extremes in some clean rooms I've seen. It is as much about the psychology of putting on special clothing and adhering to procedures as it is to physical protection, like FOD and anti static procedures: once you've gone to that trouble you instinctively buy into the mantra, which is good because it becomes a natural part of your working day rather than being perceived as a chore. I remember being berated once for committing the cardinal sin of bringing in a newspaper once into a clean room, before newspapers were all online (there was an article in it about our project). Needless to say, I won't be doing that again.

author: Mechanical Menace
author_rank: Super Contributor
timestamp: February 27, 2015, 11:05:03 am
content: Quote from: PsychoMaster on February 27, 2015, 10:28:54 amIt's not fair to advertise specs you don't meet. I don't think anyone would have a thing wrong to say about them if they were honest about their products.I don't whine that cheap instant coffee isn't as nice as freshly ground. I would whine if someone was advertising freshly ground but sold me a cup of cheap instant...

author: rollatorwieltje
author_rank: Unknown
timestamp: February 27, 2015, 11:07:47 am
content: Ask your local trade commision what they think about lying on products, especially when it considers safety ratings.The thing is, nobody would make a fuss if the multimeter said it was only for CAT I circuits. No problems for professionals, no problems for hobbyists, no problems with the law. If you decide to use that CAT I meter on a CAT III circuit, that's your problem. But these manufactures basically say they don't give a shit about your life by claiming CAT III or even IV even though they would never safely deal with a fault condition on these circuits.

author: tszaboo
author_rank: Super Contributor
timestamp: February 27, 2015, 11:09:12 am
content: These meters very well might work for 20 years, and there could be huge changes on the view we are having about a certain brand. Think about the BTTF Japan reference. 20 Years from now, your kid might use it to fix his hoverboard, measuring 600V DC with it. And he expects one of those superior chinese products.Lying about a safety feature is potentially killing someone, should be treated like attempted murder.

author: John Coloccia
author_rank: Super Contributor
timestamp: February 27, 2015, 11:11:23 am
content: Is this a serious thread? Just off the top of my head, a lot of hobbyists buy these sorts of meters to play around with their tube amps, with many hundreds of volts running around inside. I guess they should just die for being stupid and not being able to figure out by looking at the picture if a meter really meets it's safety rating.

author: Howardlong
author_rank: Super Contributor
timestamp: February 27, 2015, 11:24:53 am
content: To bastardise a well known phrase, there are two types of EEs, those EEs who've had an electric shock, and those who will.And in almost all cases, it'll have nothing to do with the CAT rating (or lack of it) of a meter. It'll be down to the EE's own mistake. (Well that's based on my own experience anyway, and Darwin hasn't succeeded yet in my case).

author: John Coloccia
author_rank: Super Contributor
timestamp: February 27, 2015, 01:44:49 pm
content: Maybe under the little Cat III-600V label, they should stick another little label that says, "Warning! Only for use on Arduinos."

author: xrunner
author_rank: Super Contributor
timestamp: February 27, 2015, 01:55:42 pm
content: This thread isn't going to end well.

author: IanB
author_rank: Super Contributor
timestamp: February 27, 2015, 02:29:17 pm
content: Quote from: John Coloccia on February 27, 2015, 11:11:23 amA tube amp circuit is plugged into a domestic mains outlet and (normally) has an H.V. isolation transformer between the tubes and the mains. It is less than CAT I. There is not enough energy present to cause arc flash injuries or explosions.

author: IanB
author_rank: Super Contributor
timestamp: February 27, 2015, 02:32:26 pm
content: Quote from: rollatorwieltje on February 27, 2015, 11:07:47 amThe thing is, I bet they would. People would say, "Oh, it's only CAT I, it's crap!"Apparently there is an expectation today that all meters will have CAT III/CAT IV printed on them. The manufacturers merely oblige. It is called "the law of unintended consequences".

author: Tandy
author_rank: Frequent Contributor
timestamp: February 27, 2015, 02:48:20 pm
content: I think the manufacturers of these meters are doing themselves a disservice by putting markings on them that they are not capable of meeting.Most average DIYer has no idea what the CAT ratings are so they may as well not even bother with the markings.Some hobbyists have idea but as most don't go anywhere near high voltages they don't really need a CAT 4Professionals would only buy quality brands anyway so wouldn't give these cheap things a second glance.They may just as well put no CAT marking on them, they would sell just as well to the kind of customer that is looking to buy them and at the same time not be misleading people.

author: Corporate666
author_rank: Unknown
timestamp: February 27, 2015, 03:00:03 pm
content: Quote from: PsychoMaster on February 27, 2015, 10:28:54 amThere is a place for Chinese junk... but why do they need to label it as something more than it is? If people aren't working on dangerous voltages, then the Chinese don't need to claim that their meters meet the appropriate safety standards.And it seems entirely unreasonable to me to expect the buyer of a cheap Chinese POS product to determine how safe it is for various applications. I'd say a hobbyist/newbie/casual user is the *least* qualified person to open up a meter and make a judgment about it's suitability for purpose. The only reason the Chinese manufacturers are lying is to give the impression that their product IS suitable for those purposes, and that's downright dangerous.In other words, they are not merely neglecting to warn against such use, they are actively advertising suitability for such use. That kind of thing can get someone killed.

author: AlfBaz
author_rank: Super Contributor
timestamp: February 27, 2015, 03:12:03 pm
content: Bullshit CAT ratings have had some pretty serious consequences. In a very large manufacturing plant nearby the perceived danger of these items have seen them ban all meters except fluke's simply because it's to time consuming for safety/engineering departments to track down and verify all the decent brands out there, so now you are only allowed to bring fluke meters on site (or so the story goes)

author: John Coloccia
author_rank: Super Contributor
timestamp: February 27, 2015, 03:14:07 pm
content: Quote from: IanB on February 27, 2015, 02:29:17 pmArc flash is way down on the list of things to worry about for anyone but industrial electricians.There's mains circuitry in there too, which means you need CAT II right off the bat, if my memory serves. But on the high voltage side, if your meter isn't designed to handle the 400V or more that are typically running around (and remember, there are large filter caps in there that can supply a lot power for brief periods of time) you can cause all sorts of arcing and damage in the meter itself. Do that enough times and then all bets are off.Manufacturers shouldn't be playing around with CAT ratings and/or the basic voltage/current ratings of their meters.

author: Howardlong
author_rank: Super Contributor
timestamp: February 27, 2015, 03:15:44 pm
content: Quote from: IanB on February 27, 2015, 02:29:17 pmI don't know about AF amps, but RF amps are almost guaranteed to be referenced to earth.

author: madires
author_rank: Super Contributor
timestamp: February 27, 2015, 03:27:06 pm
content: It's very simple, if you work on mains get proper tools, i.e. isolated screw drivers, isolated pliers and quality meters/testers/probes from known vendors. Yes, they are expensive, but your life is much more valuable than saving some bucks. If you see a tool for <1/2 of the usual price, you should be alarmed! This is common sense! And yes, the vendors lying about security related specs should be punished hard, because it could lead to the user's death.

author: IanB
author_rank: Super Contributor
timestamp: February 27, 2015, 03:33:31 pm
content: Quote from: John Coloccia on February 27, 2015, 03:14:07 pmAs far as I know CAT ratings are purely about operator safety in connection with high energy circuits. It is not about high voltages as such, and there is no expectation that the meter will remain undamaged. Your meter can be completely destroyed inside and still pass the CAT rating tests.

author: Lightages
author_rank: Unknown
timestamp: February 27, 2015, 03:41:11 pm
content: Really? The argument that "I have never had a problem so there are no problems" is a really ostrich head in the sand logic. Do we also really need to go over all of this again when it was all covered in the thread on Dave's review on the UT71E and is still being discussed?

author: John Coloccia
author_rank: Super Contributor
timestamp: February 27, 2015, 04:19:29 pm
content: Quote from: IanB on February 27, 2015, 03:33:31 pmIt's a CAT rating at a certain voltage. The voltage is very important...maybe even most important...because that determines the isolation you need. If that's botched up, all the clever little isolation slots and fuses become nothing but spark gaps. If you're rated for 600V, that means I should be able to probe 600V all day long with no problems and no damage.I used to fly aerobatics in airplanes. My typical plane was rated to 6Gs positive. That means a couple of things. First thing is I can pull 6Gs all day long without damaging the aircraft. It also means that the point of structural failure is at least 9Gs. Structural failure means that something important falls off the plane (the wings...the tail...the engine...something really important).Now that doesn't mean that I can pull 7Gs with no problem. At 7Gs, I won't suffer catastrophic failure, but I CAN damage the airplane. How much? Who knows. All I know is that once you stress it passed it's design load, somewhere between 6Gs and 9Gs there's a point where nothing falls off, but I've weakened the structure so that the 6G design load is no longer valid, and now I'm in trouble.So when the meter doesn't meet it's basic specs, and you stress it, what happens to it? The CAT part of the rating gives you an idea of how much energy the meter can absorb before something bad happens, and the voltage part of the rating gives you an idea of the maximum voltage the meter can take before the isolation fails and it can no longer meet the CAT rating. The actual catastrophic failure point is much higher, and it has to be to account for normal and expected transients and surges.

author: PsychoMaster
author_rank: Regular Contributor
timestamp: February 27, 2015, 05:20:12 pm
content: Come off it YOU KNOW you are buying stuff from a Country that is industrially lawless so if you can't under stand that then I suggest you stay away from buying from them.I think my rant is pretty self explanatory.The word CAT written on a cheap meter means about the same as MEOW,you get what you pay for. Unbelievable!Oh yea and if any body is poking around in high voltage valve stuff then my comment about not going near electricity apply.Do people really not under stand how to keep them selves safe?

author: Phaedrus
author_rank: Frequent Contributor
timestamp: February 27, 2015, 05:24:47 pm
content: It sounds like you're being an apologist for lawbreakers and counterfeiters, by saying that you should *expect* an inexpensive product to be unsafe. Should we also expect cheap milk to be full of melamine? Should we expect cheap hamburger to be made of horse? Should we expect inexpensive PSUs to have insufficient isolation and grounding?This fallacy is something I encounter quite frequently, but I don't know the technical term for it. But I have learned that people that fall prey to it are usually not worth listening to.EDIT: I should make a note regarding my wording. "Expect" is perhaps the wrong word: the correct term would be "accept". We should expect those things currently because those are scams that currently exist. But just because those scams exist does not mean that we should accept their existence and give up fighting against them. To do so is tantamount to endorsement.

author: IanB
author_rank: Super Contributor
timestamp: February 27, 2015, 05:40:47 pm
content: Quote from: John Coloccia on February 27, 2015, 04:19:29 pmActually, no, I don't believe so. If you happen to probe a three phase 600 V bus bar while accidentally having your meter on the amps range, then your meter may not survive without damage. The important thing is thatyouwill survive without too much damage (assuming you are wearing the appropriate PPE).To use the flying analogy, if you goof up your plane may crash but you at least have a parachute.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: February 27, 2015, 05:41:04 pm
content: A lot of wordsmithing going on here, but one of life's rules is that if something seems to be to good to be true, it probably isn't.So when I see a meter at a price point that is too good to be true, I should expect that it isn't true in some sense. Why it isn't may be worth further investigation. Is it a loss leader? Is it stolen? Is it fraud?The user can determine if those answers affect him or her. I use these meters a lot. On low energy, low voltage applications. I work on high voltage, high energy applications as rarely as possible, and when I do I use higher quality equipment. But even then, the protections inherent in the equipment are among the least important of the precautions I take. Complacency about the safety features of equipment is as hazardous as using less safe equipment.

author: G7PSK
author_rank: Super Contributor
timestamp: February 27, 2015, 05:46:13 pm
content: The thing about the high voltage tube amps is that they are not really high energy, the HT from the transformer may well be a 1000 volts or more but it will not produce KA of power as can be had from the grid and that is what the cat rating of the meter is supposed to protect you from. I have a UT61E but I would never use it to measure a high power circuit as I know it's rating is not really any more than CAT2 so I keep a couple of other meters for the high power stuff but they have higher burden voltage ans less sensitivity in the current range but on power circuits that is not really a problem. It could be said that some one could take the UT61E from my bench and blow themselves up but as the only one to have access to that is my wife and she does not know what a meter is let alone how to connect it to the mains I am not worried.

author: Mechanical Menace
author_rank: Super Contributor
timestamp: February 27, 2015, 05:50:29 pm
content: Quote from: PsychoMaster on February 27, 2015, 05:20:12 pmAnd what about the rebadged stuff sold over here? Even well known vendors carry that stuff and claim they meet the specs.QuoteActually not everything cheap lies about their specs.QuoteSometimes you get charged a "proper" amount for cheap crap.QuoteYou buy something advertised by UK sellers as having a certain safety rating you expect it to be true.

author: PsychoMaster
author_rank: Regular Contributor
timestamp: February 27, 2015, 05:53:24 pm
content: If we are not careful we are going to wind up in a society where you cannot do anything because of H and S officials treating us all like morons.You and your intelligence are responsible for your safety notreally relying on something because of whats printed on it.If you actually read what I have written then it pretty much answers ,and saying I am making good for dishonest manufacturers ,where are they to blame? If they print on their products what the buyer expects to see when paying next to nothing who is being dishonest?I'll repeat again ' YOU KNOW WHAT YOU ARE BUYING'. Is all this so that you can go crying to some one if you do some thing dumb?

author: G7PSK
author_rank: Super Contributor
timestamp: February 27, 2015, 05:58:18 pm
content: I would still have bought the UT61E if had only been labled CAT2 after all that is all my scope is and I would find it surprising if any scope is CAT4 except perhaps something like the Fluke scopemeter.

author: Mechanical Menace
author_rank: Super Contributor
timestamp: February 27, 2015, 06:02:20 pm
content: Quote from: PsychoMaster on February 27, 2015, 05:53:24 pmAnd part of that is buying tools that meet safety specs you require for the job.QuoteThere isn't a teardown online of a product, it's not stupidly cheap but cheap enough to be worth the saved money (just like an amazing amount of the meters you're on about), how do you know without buying it and then braking your warranty by opening it up?It is ILLEGAL for them to put those markings on products that don't meet the standard, and still "trusted vendors" will stock them. How many dangerous USB chargers are bought from a big name shop?

author: CatalinaWOW
author_rank: Super Contributor
timestamp: February 27, 2015, 06:04:10 pm
content: Quote from: PsychoMaster on February 27, 2015, 05:53:24 pmFrom my point of view, we are already there. But it is likely to get worse.The sad part is how little value some of the protections have. In California, well meaning lawmakers passed a law requiring vendors who sold items known to contain carcinogens to post warnings. After a few rounds of lawyering it was realized that many food products contain trace amounts of carcinogens. So now all stores that sell food in that state have a warning sign. The only good it does is to block a little light in the window, and provide a tiny bit of protection from the weather.

author: G7PSK
author_rank: Super Contributor
timestamp: February 27, 2015, 06:15:21 pm
content: There should be a warning in the PRC. "Lawyers are highly toxic to your wallet"and another on birth certificates. "Warning life is fatal"that should cover everything.

author: SeanB
author_rank: Super Contributor
timestamp: February 27, 2015, 06:31:47 pm
content: That explains the little warning in the fine print" Warning, may cause cancer in California" on US made food. As it invariably also has high fructose corn syrup ( even in stuff like dry spices and meat) I stay away from it.HP sauce does not taste the same since it was bought out. I stopped using it.

author: Mechanical Menace
author_rank: Super Contributor
timestamp: February 27, 2015, 06:37:06 pm
content: Quote from: SeanB on February 27, 2015, 06:31:47 pmI can't remember what it tasted like pre 1988 but it hasn't changed as long as I can remember, though I was worried when Heinz bought it and moved production.Maybe it's one of those things that doesn't travel well, like Guinness?

author: John Coloccia
author_rank: Super Contributor
timestamp: February 27, 2015, 06:41:36 pm
content: Quote from: IanB on February 27, 2015, 05:40:47 pmI'm talking about damage to the protection mechanisms. If the ratings are fubar, you really have no idea at what point you're exceeding the actual safe limits for the device, and the day you do something stupid the protection you need may not be there.

author: IanB
author_rank: Super Contributor
timestamp: February 27, 2015, 06:52:36 pm
content: Quote from: John Coloccia on February 27, 2015, 06:41:36 pmI would imagine the protection mechanisms have to fail safe. If they are damaged they should go open circuit or high resistance and the meter should stop working.But at this point I am speculating on too much. I think it is necessary to refer to the actual specifications of the CAT safety tests and see what they require for each CAT level.

author: miguelvp
author_rank: Super Contributor
timestamp: February 27, 2015, 07:01:24 pm
content: If they don't meet regulation then you can report it to your country so the meters in question are subjected to an import ban. The question is, do they meet the regulations for the year that they were designed?Are they required to update the same models newly produced to newer regulations?Who is going to pay for the testing and dig through the paperwork that might have the appropriate exemptions if they actually do meet previous regulations and are somewhat grandfather in?I guess there is more need of proof and less assumptions. What is the actual regulation? can I use a meter while standing in a bucket of water and still be safe? or do they actually require proper handling of the device with the necessary protection external to the device itself?A piss poor design is not a big enough claim that it wont meet those regulations. Maybe contact a consumer protection group in your country to see if anything can be done to test those devices and investigate if they meet the needed standards they claim they meet?

author: Corporate666
author_rank: Unknown
timestamp: February 27, 2015, 07:37:03 pm
content: Quote from: PsychoMaster on February 27, 2015, 05:20:12 pmHow do you know you're buying junk? Or rather, how does the consumer know?Uni-T is not a particularly Chinese sounding name, and the store it's being sold in won't have a big sign saying "Chinese shit! Price is low, but you're on your own for safety".And you can't judge based on price - there are some Chinese meters which are expensive and some which are good also.And you can't judge based on where they are made either - because aren't Agilent (or was it Fluke) meters built in China these days?The premise that the onus is upon the consumer to know they should not trust the ratings is silly.

author: IanB
author_rank: Super Contributor
timestamp: February 27, 2015, 07:39:43 pm
content: I guess it would be more appropriate to check for a traceable UL certification proving that the standards were met.

author: rollatorwieltje
author_rank: Unknown
timestamp: February 27, 2015, 08:03:53 pm
content: Quote from: Corporate666 on February 27, 2015, 07:37:03 pmFluke makes some cheap models for the Chinese market. What's interesting is that they aren't sold in the EU, but the Fluke 101 I ordered came with a document stating it complies with the appropriate EN/IEC standards, written in EN/FR/DE/IT/SP. It also has a CE mark.

author: SL4P
author_rank: Super Contributor
timestamp: February 27, 2015, 08:41:05 pm
content: Quote from: IanB on February 27, 2015, 02:32:26 pmWith a BILLION potential customers - who needs return business.I want to get rich NOW.

author: SL4P
author_rank: Super Contributor
timestamp: February 27, 2015, 08:43:13 pm
content: Quote from: madires on February 27, 2015, 03:27:06 pmOK, I'll go to the store and only buy products that are displayed UL, CE, CAT III from(please insert list of known vendors here - I'm sure they're all the same across the globe)

author: SL4P
author_rank: Super Contributor
timestamp: February 27, 2015, 08:47:51 pm
content: Quote from: IanB on February 27, 2015, 06:52:36 pmYeah right. Imagining, and expecting someone else to 'do the right thing' will save lives.

author: G7PSK
author_rank: Super Contributor
timestamp: February 27, 2015, 09:38:27 pm
content: Quote from: rollatorwieltje on February 27, 2015, 08:03:53 pmThey also make some not so cheap meters for the rest of the world, I have just bought a 115 and that is designed in the US but made in China.

author: PsychoMaster
author_rank: Regular Contributor
timestamp: February 27, 2015, 10:48:41 pm
content: How did my mad rant become a debate?

author: madires
author_rank: Super Contributor
timestamp: February 28, 2015, 11:05:22 am
content: Quote from: SL4P on February 27, 2015, 08:43:13 pmscrew drivers: Wero, Wihapliers: Knippex, Wihameters/testers: Benning, Fluke

author: LordNobady
author_rank: Contributor
timestamp: March 02, 2015, 11:56:31 am
content: Quote from: IanB on February 27, 2015, 07:39:43 pmif that becomes the standard to look at them then the Chinese will print UL numbers on them. possible even from working look alike's. As long as thy can sell them thy will not stop. the only way is not to by them.

author: Sigmoid
author_rank: Frequent Contributor
timestamp: March 02, 2015, 05:03:16 pm
content: Quote from: Howardlong on February 27, 2015, 11:24:53 amThat doesn't mean that silkscreening bullshit CAT ratings on stuff is in any way acceptable.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: March 02, 2015, 06:38:33 pm
content: Yeah it's unacceptable. But it is also unacceptable to run red lights and to stick a knife in a persons gut and demand their money. Laws against these behaviors don't mean they don't happen. That is why sensible people look before driving off at a green light, and don't visit places where nasty people with knives are likely to be. Or they carry their own knife and bring a huge friend. The latter example is the analog to buying cheap equipment and using it with caution. It isn't for everyone.