Author Topic: EEVblog #1007 - Is a $25 Multimeter Any Good  (Read 97879 times)

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Offline f4eru

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Re: EEVblog #1007 - Is a $25 Multimeter Any Good
« Reply #25 on: July 15, 2017, 02:30:56 pm »

If you're worried you can scratch off a I and get a more realistic rating.


Not a good idea. If you "remark" it to some non compliant safey marking, you're responsible if somebody gets hurt.
(in the EU, you're fully legally responsible now anyway if you import or resell it, which includes buying it from alibaba or ebay china, or amazon not UE)
« Last Edit: July 15, 2017, 02:35:25 pm by f4eru »
 

Offline Fungus

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Re: EEVblog #1007 - Is a $25 Multimeter Any Good
« Reply #26 on: July 15, 2017, 02:31:54 pm »
If I dindn't already have a Fluke 101, I would buy this thing :-+

What country are you from? Is there a law against owning both?

I bought one of these to use as a secondary meter to my old Fluke 27

(or primary, I can't promise which one will be used most in practice)

If it is possible to replace the fuse holders with something bigger, I will give it a go.
.

If you're using this in a place where you need bigger fuses, you're probably doing it wrong. When would you ever be measuring current in a 4kV transient-prone environment anyway?  :popcorn: (the current ranges are the only places the fuses are doing anything useful).

Another thing to ponder is that the battery voltage appears on the square wave output. Think about that long and hard before connecting it to mains AC with the selector in that position.  :scared:

One good thing about this meter is that they put the current ranges/square wave selections as far as possible from the "OFF" position. That's a bigger safety feature than bigger fuses will be.

Dave,

products like this and an iffy economy are why, if I were you, I would not risk your future finances on the success of your meter, nomatter how good it is, we can never compete on price with the Chinese..  we shouldn't even try.

We have to work smarter, and make smarter products, not cheaper.

A smart thing would be to add proper MOVs, PTCs and fuses and sell it for $40.

(and put temperature function instead of square wave output)


In other news: The sibling AN8002 survived longer than a Fluke 87V in joe's electrical robustness testing. There's no reason to think this will be different, the PCBs are almost identical.

https://www.eevblog.com/forum/testgear/hear-kitty-kitty-kitty-nope-not-that-kind-of-cat/

 :popcorn:
While that is encouraging, that says little about safety.

I know, I'm just trolling you.

My advice for anybody who:
a) Wants to poke pieces of metal into mains sockets and distribution panels
and
b) Thinks a proper industrial meter is "too expensive"

is to get a Fluke 101. They're only $42, delivered. There's really no excuse.

Also: The multimeter is only a part of the equation. I'd prefer to use this meter on a distribution panel with gloves, face shield, hearing protection and a partner standing by with telephone in hand than a "safe" Fluke 87V without any of those things.
« Last Edit: July 15, 2017, 02:43:26 pm by Fungus »
 

Offline Rbastler

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Re: EEVblog #1007 - Is a $25 Multimeter Any Good
« Reply #27 on: July 15, 2017, 04:08:58 pm »
If I dindn't already have a Fluke 101, I would buy this thing :-+

What country are you from? Is there a law against owning both?

I bought one of these to use as a secondary meter to my old Fluke 27

(or primary, I can't promise which one will be used most in practice)


I originally bought the Fluke 101 to always have a nice little meter with in my backpack and also the have a meter I can trust during holidays, where I can't acess the rest of my gear. Since I have that, I don't really see the need for another meter. But I use mostly a Fluke 177 or a DM3068.
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Offline alm

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Re: EEVblog #1007 - Is a $25 Multimeter Any Good
« Reply #28 on: July 15, 2017, 04:41:28 pm »
My advice for anybody who:
a) Wants to poke pieces of metal into mains sockets and distribution panels
and
b) Thinks a proper industrial meter is "too expensive"

is to get a Fluke 101. They're only $42, delivered. There's really no excuse.
Well, that is more than twice as expensive :P. I would agree, if this thing would not state 'please use me on three-phase motors', i.e. CAT III 600 V, on its front panel. Then it would make a fine companion to a meter like that.

Also: The multimeter is only a part of the equation. I'd prefer to use this meter on a distribution panel with gloves, face shield, hearing protection and a partner standing by with telephone in hand than a "safe" Fluke 87V without any of those things.
Absolutely. But that is not a very fair comparison. The few hundred USD you save by going for the $20 meter does not pay for that safety equipment, especially not the partner.
 

Offline npelov

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Re: EEVblog #1007 - Is a $25 Multimeter Any Good
« Reply #29 on: July 15, 2017, 05:31:24 pm »
What is the cut off voltage. Can it be used with Ni-Mh?
 

Offline plazma

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Re: EEVblog #1007 - Is a $25 Multimeter Any Good
« Reply #30 on: July 15, 2017, 05:34:14 pm »
What is the cut off voltage. Can it be used with Ni-Mh?
The AN8002 model works fine with LSD NiMH cells.
 

Offline b_force

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Re: EEVblog #1007 - Is a $25 Multimeter Any Good
« Reply #31 on: July 15, 2017, 08:15:30 pm »
20 bucks.

Just modify it with some proper input protection yourself.
And there is even a work-around for the current ranges (witch really is a bummer, i agree)
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Offline rollatorwieltje

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Re: EEVblog #1007 - Is a $25 Multimeter Any Good
« Reply #32 on: July 15, 2017, 08:26:01 pm »
I would love to see what a tiny fuse like that does when shorted across mains. I suspect it's not really a problem that those fuses normally come with leads, you're probably going to need them.
 

Offline electr_peter

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Re: EEVblog #1007 - Is a $25 Multimeter Any Good
« Reply #33 on: July 15, 2017, 08:34:40 pm »
It seems that volt range has [000.0 - 999.9 mV] range as well (that is, both V and mV ranges on the same switch position). Thus DMM can show [230.1 mV] or [230.1 V] - 1000 times difference in magnitude, but display only differs by a small letter.
This display behaviour can be annoying and misleading for many people. I do not like such configuration - better to have separate [V] and [mV] ranges, not a strange mix as it is.
 
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Offline Lightages

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Re: EEVblog #1007 - Is a $25 Multimeter Any Good
« Reply #34 on: July 15, 2017, 09:08:27 pm »
When people talk about modifying a multimeter to make its input protection "better", I cringe. You might be able to reliably improve the sensitivity of the meter to damage and failure. Don't fool yourself into thinking that the meter is safer for the user.

Multimeters go through extensive pre-testing, and testing in approved third party labs to obtain a proper certification. Safety is not something guaranteed by design, that is why testing is done. Sure you can add resistors, MOVs, spark gaps, PTCs, fuses, etc to the input circuits and they might improve the reliability of the meter itself to withstand user errors and  unexpected transients. This is no guarantee that under the wrong circumstances that the meter won't explode and nor that your mods will have not made the meter worse for your safety.

Joe has done many tests and his thread was originally something to with matching CAT ratings, but he has edited the title to remove this association and for good reason. Joe has also modified meters to make them, the meters themselves, survive HIS tests. His tests are not safety tests. They might have a some relation to the safety of a meter but that is not his goal nor should the results infer any safety level of the meters he tests. It is quite possible, even likely, that his modified UT61E will pass CATIII/600V without any problems, but it has not been tested under the requirements for that rating and that means it actually could be a bigger bomb in your hand under the wrong circumstances than the original.

My point for ranting here is that when people casually mention modifying their meters to better the input protection they either have no idea what they are saying, have no idea what safety actually implies, but even worse they might give the casual reader the idea that modifying a multimeter is automatically a good thing and nothing could go wrong.

If a meter needs modification to make it safe, mark it as "NOT SAFE FOR FOR ELECTRICAL WORK" and/or "DOES NOT MEET ITS SAFETY RATINGS". That should be the only modification made to any meter that someone might think is safe to use in any situation other than the low energy electronics work bench. That is unless the mods are solely for added functionality or survivability on the bench.

Sure, modifying is fun, can be useful, educational, and even money saving, but it cannot imply better safety. If you modify a meter, keep it on the bench and mark it as mentioned before. It should never be used on anything higher than CATII, maybe even CATI.
 

Online ebastler

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Re: EEVblog #1007 - Is a $25 Multimeter Any Good
« Reply #35 on: July 15, 2017, 09:29:04 pm »
I originally bought the Fluke 101 to always have a nice little meter with in my backpack and also the have a meter I can trust during holidays, where I can't acess the rest of my gear. Since I have that, I don't really see the need for another meter.

Well, depends whether "during holidays" you are more likely to measure mains voltage (which you would rather not do with the AN8008), or to measure any current (which the Fluke 101 can't do at all)...

Regards from ebastler to Rbastler, by the way!  ;)
I assume you are from the German-speaking part of Italy? Happy tinkering! (A "bastler" is "tinkerer", for all non-Germans out there.)
 

Offline Rbastler

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Re: EEVblog #1007 - Is a $25 Multimeter Any Good
« Reply #36 on: July 15, 2017, 09:29:58 pm »
I think modifying cheap gear into better one isn't worth it, because you spent time and money into creating something better and in the end it did cost the same amount as if you'd bought the more expensive one.
I see a reason in doing it, when a particular function isn't available on the more expensive multimeter for example.
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Offline b_force

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Re: EEVblog #1007 - Is a $25 Multimeter Any Good
« Reply #37 on: July 15, 2017, 09:39:18 pm »
My point for ranting here is that when people casually mention modifying their meters to better the input protection they either have no idea what they are saying, have no idea what safety actually implies, but even worse they might give the casual reader the idea that modifying a multimeter is automatically a good thing and nothing could go wrong.
In my professional opinion, you clearly ARE missing the point and thinking in ways of rules, not in a way of circuit design.

1- Safety tests go much further than just peoples safety.

2(a,b&c) - Safety tests are also mainly focused how to have consistent safety in production in masses.
On top of that those type of product should never fail in a professional setup (you can get very awkward and annoying situations)
Plus a company doesn't want some bizarre case in court, so they do whatever they can to provide proof that every lunatic can use their product in every thinkable (bizarre and weird) situation

Those are two VERY different things!!

Someone with enough knowledge and a clever design can even make this $20, 99.8% safe without any issues.
And that doesn't need to be expensive.

So by just ranting that people don't have clue about safety is absolutely nonsense without any context.
Than I am simply gonna rant back  8)
« Last Edit: July 15, 2017, 09:46:08 pm by b_force »
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Offline Lightages

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Re: EEVblog #1007 - Is a $25 Multimeter Any Good
« Reply #38 on: July 15, 2017, 10:16:36 pm »
Someone with enough knowledge and a clever design can even make this $20, 99.8% safe without any issues.
And that doesn't need to be expensive.

Prove it. Prove it with proper safety tests done by approved safety testing facilities, testing equipment modified by people who "have enough knowledge". Prove that these modified meters are safer for the user. That is prove in what safety means in the context of CAT ratings. I also qualified the benefits of modifications but you seem to want to pick a fight over something that I didn't say.

So by just ranting that people don't have clue about safety is absolutely nonsense without any context.
Than I am simply gonna rant back  8)

Again, you are putting words in my mouth. When did I say that everyone has no idea of safety? My content is what Joe has said about his tests himself, what the IEC has said about safety tests, what Dave has said about safety and meter construction, what I have as 30+ years in safety and health education, certifications, and building equipment to safety standards and inspections by CSA and UL.

If you want to make recommendations that people should make modifications to multimeters to improve the safety of the user, then you are making dangerous recommendations unless you have certified tests to prove your assertions. In this case you are an uneducated, unscientific, and dangerous idiot.
 

Offline npelov

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Re: EEVblog #1007 - Is a $25 Multimeter Any Good
« Reply #39 on: July 15, 2017, 10:45:21 pm »
Guys don't fight!
Personally I think if you need a safe multimeter - you get one. You don't fool around and try to make it any safer than it is. I tried to be friend with electricity many times and it kicks me every time. So whenever I poke at line voltage I don't take any chances. The good expensive HRC fuses have one advantage - it's less likely to blow it because you know you'll pay another $15 for new one and you are extra careful. The fuses in my Brymen are more expensive than this multimeter! Damn, I don't want to make this one safer because I'll be scared to use the current measurement and blow an expensive fuse just because I probed 5V line. You don't wear bulletproof vest when you play with water guns.
 

Offline b_force

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Re: EEVblog #1007 - Is a $25 Multimeter Any Good
« Reply #40 on: July 15, 2017, 10:47:06 pm »
You can name all the safety certificates you want (which I am all aware off).

A very respected, smart and highly intelligent person in science and engineering with over 50 years of experience, ones told me the following (unfortunately I'm not allowed to share his name in public)

"People always say safety first. Which is very incorrect and even dangerous.
It is thinking first (just follow basic science and engineering), than safety and third is sometimes just random bad luck"

In fact, it is even proven that blindly following safety protocols can even lead to potentially more dangerous situations.
You should teach people the how and why instead.

With me a lot of people in the field are getting extremely sick of all the ridiculous so called 'safety rules'.
You can write pages about how many years of experience you have and what kind of qualifications or certificates etc, but it all simply comes down to some general science knowledge.
Because it simply doesn't make sense why nobody cares about batteries, while it doesn't cost much to kill someone very easily with a 9V battery!
I know companies/countries where someone isn't even allowed to handle a bloody standard knife anymore  |O :palm: :palm:
If people are to dumb to know what they are doing, they shouldn't be doing it in the first place.
In fact, in a lot of countries that's even how the law system work.
Which means that it's not important anymore if a product was 'unsafe', just by the fact that you were doing things you weren't qualified for cancels everything out.

Btw, with all the respect, but I don't know who brainwashed people that 'you need approved safety facilities' to test safety.
Than you simply have fallen in the big marketing trap.
You forget the reason WHY these facilities exist, with the one and only reason: cover themselves in court.
Nothing more, nothing less. That doesn't mean that other ways aren't safe.
(in fact I know many so called 'safety regulations' in some countries that are absolutely forbidden in others)
Second to that, if safety is so important, why is it SO difficult and SO expensive to get these tests done, of to even get the basic documents?
These things should be open to the public.

All of this doesn't mean that there are people out there that make these type of meters, review a lot of meters or just have a very good understanding what potential dangerous there are and how to tackle them or are just smart people with enough knowledge/resources to find that out.
These meters and safety tests are not done by unknown hyper smart aliens.

So in fact, I would ENCOURAGE people to dig into this and share it to the public because in my opinion that's even your responsibility as an engineer/scientist.
And to add something extra for the people who have so "many experience in the field", maybe it would be better to help people out, explain it how it is done properly instead of kicking people shins.
If you can make the time and energy to rant, you can also use the same time and energy to be productive instead.
Talking about proving.......




 
« Last Edit: July 15, 2017, 10:51:31 pm by b_force »
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Offline digsys

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Re: EEVblog #1007 - Is a $25 Multimeter Any Good
« Reply #41 on: July 15, 2017, 11:58:25 pm »
I'm NOT going to buy one ... I'm NOT going to buy one ... I'm NOT going to buy one ... I'm NOT going to buy five ... DOH !!
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Offline joeqsmith

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Re: EEVblog #1007 - Is a $25 Multimeter Any Good
« Reply #42 on: July 16, 2017, 02:31:35 am »
When people talk about modifying a multimeter to make its input protection "better", I cringe. You might be able to reliably improve the sensitivity of the meter to damage and failure. Don't fool yourself into thinking that the meter is safer for the user.
...
Joe has done many tests and his thread was originally something to with matching CAT ratings, but he has edited the title to remove this association and for good reason. Joe has also modified meters to make them, the meters themselves, survive HIS tests. His tests are not safety tests. They might have a some relation to the safety of a meter but that is not his goal nor should the results infer any safety level of the meters he tests. It is quite possible, even likely, that his modified UT61E will pass CATIII/600V without any problems, but it has not been tested under the requirements for that rating and that means it actually could be a bigger bomb in your hand under the wrong circumstances than the original.

My point for ranting here is that when people casually mention modifying their meters to better the input protection they either have no idea what they are saying, have no idea what safety actually implies, but even worse they might give the casual reader the idea that modifying a multimeter is automatically a good thing and nothing could go wrong.
.....
Sure, modifying is fun, can be useful, educational, and even money saving, but it cannot imply better safety. If you modify a meter, keep it on the bench and mark it as mentioned before. It should never be used on anything higher than CATII, maybe even CATI.

My highly modified UNI-T UT61E is more robust, has lower burden voltage and a much low temperature coefficient than it did when I bought it.  Not to mention it's adaptive backlight and that it can measure 20A for extended periods of time.    You would have to be a complete idiot to think it was safe.   It looks more like a death trap. 

You are right that when I modify them, it is to pass my tests which are different from the IEC standards.  The main differences being the double the FWHH and much lower available energy.  The energy really only comes into play if a meter were to breakdown.  We just don't see the level of explosions you will see with a real combo generator.   However if the meter does not breakdown, that energy is absorbed by the generator (not the meter) and in these cases, I would expect the meter to handle the same levels on a certified combo generator.   This is why when we had a member repeat the testing I did on the Fluke 101 at 12KV, it had no problems.   If we took Dave's 121GW for example that failed at 1.5KV 2KV, putting it on a real surge generator we may see some action.  While the meter may not survive or be repairable after such a test, we will assume it is safe per the standard. 

I've mentioned it before that I think the majority of the safety would be mechanical.  I suspect the protection circuitry on the voltage input is really there to prevent damage to the meter, not for safety.  I have a TPI / Summit  meter that I tested and it failed just by rotating the selector switch through the settings with the 220V applied.   It's happened four times now, so fairly rare.   This meter was UL approved to meet the safety standards.  Someone wrote that companies will falsify the cert but UL does maintain an on-line database that makes it simple enough to check.     Dave's preproduction 121GW failed at 2KV with it's MOVs, PTCs and clamps.  The AN8002 (lower end version) failed at 3KV, with just a PTC and clamp.  Dave has stated that if the 121GW passes the safety tests, it's good enough. 


With me a lot of people in the field are getting extremely sick of all the ridiculous so called 'safety rules'.
You can write pages about how many years of experience you have and what kind of qualifications or certificates etc, but it all simply comes down to some general science knowledge.

.....

Btw, with all the respect, but I don't know who brainwashed people that 'you need approved safety facilities' to test safety.
Than you simply have fallen in the big marketing trap.
You forget the reason WHY these facilities exist, with the one and only reason: cover themselves in court.
Nothing more, nothing less. That doesn't mean that other ways aren't safe.
(in fact I know many so called 'safety regulations' in some countries that are absolutely forbidden in others)
Second to that, if safety is so important, why is it SO difficult and SO expensive to get these tests done, of to even get the basic documents?
These things should be open to the public.

All of this doesn't mean that there are people out there that make these type of meters, review a lot of meters or just have a very good understanding what potential dangerous there are and how to tackle them or are just smart people with enough knowledge/resources to find that out.
....

I agree that the IEC standards should be public domain.  I'm sure you are aware that the standards are more than just for safety.  My guess is you are just referring to the 61010 standard that most of the meter's documents will call out. 

The cost to setup a lab like this is going to be more overhead than most companies could afford.  Care to guess at the price of the large compliance chamber I showed? 

Interesting comment about "getting extremely sick of all the ridiculous" safety regulations.  I have to venture out of my hole from time to time and am always amazed at the level rules at some places I visit.  While many are safety related, a fair number of them are in place for process control.   Today I visited a large power plant which really gave me a whole new perspective on electrical safety.     

I agree with your comment that just because a company self certified, does not mean the product is not safe or would fail if tested at an independent lab.  But I doubt very much that this particular meter would pass the CAT III levels. 
« Last Edit: July 16, 2017, 03:24:18 pm by joeqsmith »
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Online Brumby

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Re: EEVblog #1007 - Is a $25 Multimeter Any Good
« Reply #43 on: July 16, 2017, 03:44:14 am »
When people talk about modifying a multimeter to make its input protection "better", I cringe.

So do I.

Quote
You might be able to reliably improve the sensitivity of the meter to damage and failure.

... which is not impossible, but ...

Quote
Don't fool yourself into thinking that the meter is safer for the user.
BINGO!
 

Offline amspire

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Re: EEVblog #1007 - Is a $25 Multimeter Any Good
« Reply #44 on: July 16, 2017, 04:16:59 am »
Don't fool yourself into thinking that the meter is safer for the user.
BINGO!
Doesn't make much sense to me. If you make a meter safer, then it is in fact safer.

Some of us have some experience in electronic design. Issues like voltage clearance, fuse rating, etc are all understandable design problems. If I modified a meter for my own use, I would be comfortable.
 

Offline boffin

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Re: EEVblog #1007 - Is a $25 Multimeter Any Good
« Reply #45 on: July 16, 2017, 04:41:44 am »
Given the lack of a couple important mA ranges (likely the MOST important ones), I doubt I'd be interested in this, nor recommend it.  However, does the AN8002 have those ranges?  I'm always on the lookout to suggest things to people getting started; and for under $20, the 8002 looks like it does most of what beginner makers need (including useful Freq Counter/Duty Cycle)
 

Offline sleemanj

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Re: EEVblog #1007 - Is a $25 Multimeter Any Good
« Reply #46 on: July 16, 2017, 04:45:05 am »
Sometimes I think some people would only be satisfied if every meter was Cat IV 1000V - and even then they would worry that somebody might pick it up and connect it to a lightning rod, in a storm, in Darwin, while standing in a puddle of salt water, naked, and surrounded by crocodiles.  A Fluke would be fine in that scenario of course, patentend croc-repellant in the special yellow plastic I expect.

How many hours do people spend reading EEVBlog forum using a tablet connected to a mains charger... I wonder how well the average mains charger would fare when a 6000V impulse comes down the wire (Cat II 1000V), but we don't really give it a second thought.
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Offline alm

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Re: EEVblog #1007 - Is a $25 Multimeter Any Good
« Reply #47 on: July 16, 2017, 04:46:08 am »
I do not think a meter that clearly lies about its safety should be recommended to beginners. I am not at all claiming that beginners need a meter designed for industrial use. I would actually be fine with a meter that can not measure mains voltages. But at least it should be honest about it, since beginners will not be able to judge this for themselves.
 

Offline sleemanj

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Re: EEVblog #1007 - Is a $25 Multimeter Any Good
« Reply #48 on: July 16, 2017, 04:51:03 am »
.  However, does the AN8002 have those ranges?

The 8002 (RM102, KT102.... ) has a 60mA range (6000 count), so yes it will give you 2 digits after the decimal for 1-60mA before it steps up.  However it does not have uA ranges (at least not without modification?).

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Offline alm

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Re: EEVblog #1007 - Is a $25 Multimeter Any Good
« Reply #49 on: July 16, 2017, 05:09:54 am »
Sometimes I think some people would only be satisfied if every meter was Cat IV 1000V - and even then they would worry that somebody might pick it up and connect it to a lightning rod, in a storm, in Darwin, while standing in a puddle of salt water, naked, and surrounded by crocodiles.  A Fluke would be fine in that scenario of course, patentend croc-repellant in the special yellow plastic I expect.
Most people (including me) complain about the false labeling, giving a false sense of safety. The manufacturer was the one that brought up the ridiculous CAT III 600 V rating. In my opinion CAT I 50 V would be perfectly fine for a beginner or as a second meter for many experienced people, with the understanding that it is not to be used near high voltage or mains circuits (which a beginner should not be messing with anyway).

How many hours do people spend reading EEVBlog forum using a tablet connected to a mains charger... I wonder how well the average mains charger would fare when a 6000V impulse comes down the wire (Cat II 1000V), but we don't really give it a second thought.
First, a charger is not designed for a 1000 V circuit. So if anything, it would be CAT II 300 V (never mind that IEC61010 does not apply to chargers). And to answer your question, IEC60950 (which I believe would be applicable) requires a Hi-pot test of 3000 VAC / 4000 VDC for 60 seconds. So while being a different test from the transient used by IEC61010, it is not that far off.
 


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