EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)

[Fungus]

I am so tired of hearing the argument: "I stick my tongue in on the wires on the power poles out side and nothing ever happens to me!"

Me too Light, me too.

Yep. If it was child safety seat ratings there'd be a national scandal and daytime TV would be demanding action!!!

Here we say "Don't buy Uni-T meters because they're overpriced and lie about the safety ratings" and people are actually stepping up to defend them.

Yes it's true that child safety seat ratings aren't critical so long as you don't crash your car, but that's not the point, is it?

[rsjsouza]

I am so tired of hearing the argument: "I stick my tongue in on the wires on the power poles out side and nothing ever happens to me!" Well I have driven the same distance as that from the Earth to the moon, twice, in my lifetime, and I have not died in a car accident. WTF does that have to do with the millions of people who have died from car accidents? Safety rules and regulations have been put in place because of those who have had problems, not those who have never had problems. If you have never had a problem it could be because of all the other people who have been injured or killed before you.

Go ahead, take the risk. I DON'T CARE IF YOU DON'T. I care about the people who are uneducated and care to learn. If you don't want to learn, then stop complaining and go away.

As you know, Lightages, this argument is not new nor it seems to change. As I said 1-¹/₂ years ago on this thread:
"Hey, you know, I'm probably a bit biased here because I'm a pro and so I have seen or heard horrible stories and experienced some bad scenarios that convinced me that I wouldn't personally use that [insert tool], but if you are really sure you will use within it's limitations, which realistically is probably all you want, don't underestimate that accidents usually happen under stress, tiredness or distraction and this will not be fine."

[Fungus]

don't underestimate that accidents usually happen under stress, tiredness or distraction and this will not be fine."

Yep.

I the story I posted about the exploding multimeter that killed two people and badly burned another the multimeter being used by the electrician was borrowed from the maintenance department of the shopping mall where the problem was.

If the multimeter is a known brand, looks impressive and says "CAT IV" on it... then you'd probably use it, too. Right? Even Dave probably would have used it before he opened this one up and looked inside.

Nobody should be defending Uni-T. We should be condemning them as loudly as possible for putting death-traps out in the world and making sure that everybody knows that their brand name isn't to be trusted.

[Quarlo Klobrigney]

Yep.
I the story I posted about the exploding multimeter that killed two people and badly burned another the multimeter being used by the electrician was borrowed from the maintenance department of the shopping mall where the problem was.

Excuse me, the story who posted? That was me that posted that not you.

[Kjelt]

That was an impressive good "Office space" imitation there Dave at 16:33 "Hmmmmmm Yeaaaaaaa" 

Compare it with the original at 0:16

[Fungus]

Yep.
I the story I posted about the exploding multimeter that killed two people and badly burned another the multimeter being used by the electrician was borrowed from the maintenance department of the shopping mall where the problem was.

Excuse me, the story who posted? That was me that posted that not you.

??

I posted it here:

https://www.eevblog.com/forum/blog/eevblog-712-uni-t-ut71e-multimeter-%28why-uni-t-meters-suck%29/msg604706/#msg604706

[Lightages]

Really guys? Fighting over who posted a link to a web page? 

[Fungus]

Really guys? Fighting over who posted a link to a web page? 

 

Not really. I looked at his posting history ( https://www.eevblog.com/forum/profile/?area=showposts;u=88216 ) and I can't see that he's ever posted anything related to an exploding multimeter. Certainly not in this thread.

Soooo .... No, I don't give a damn who posted what, I was just curious where this was heading.

[Quarlo Klobrigney]

Really guys? Fighting over who posted a link to a web page? 

 

Not really. I looked at his posting history ( https://www.eevblog.com/forum/profile/?area=showposts;u=88216 ) and I can't see that he's ever posted anything related to an exploding multimeter. Certainly not in this thread.

Soooo .... No, I don't give a damn who posted what, I was just curious where this was heading.

Well I care, not fighting just some people like to say that they were first with the revelation.
If you would like to find where and where I posted it, it is here on page 9 where I excuse myself if it had been posted earlier.  https://www.eevblog.com/forum/blog/eevblog-712-uni-t-ut71e-multimeter-(why-uni-t-meters-suck)/120/?action=post;u=604114 I saw that you did this before giving no credit to me for posting it and the second time I spoke up. It was spoken about for many pages prior to your discovering it no doubt on page 9, then you reposted it on page 15 "for the first time"
Perhaps your moniker suits you well.

[TheEPROM9]

Dave shows why Uni-T multimeters generally suck in this teardown (and a little bit of a review) of the $180 UT71E 0.025% accuracy multimeter with power measurement capability.
He also opens the UT71A, UT61E, and compares the input protection and rating with a Brymen BM257.

http://uni-trend.com/UT71E.html
MAX6190 Voltage Reference: http://datasheets.maximintegrated.com/en/ds/MAX6190-MAX6198.pdf
OP1177 Opamp: http://www.analog.com/static/imported-files/data_sheets/OP1177_2177_4177.pdf
Cyrustek ES51922 DMM chipset: http://www.cyrustek.com.tw/spec/ES51922.pdf
Holtek HT1621 LCD driver: http://www.ywslcm.com/Upload/tbDownload/2013-4-13_9_37_49.pdf
AD636 True RMS Converter chip: http://www.analog.com/static/imported-files/data_sheets/AD636.pdf

One does wonder how these meters that don't meet their rating make it into the main stream market place. Bearing in mind false advertising is illegal and a lot of multimeter company's are responsible for this. To those who bash Dave in this video it is dam essential that these company's are held up and exposed for not making a product as advertised.

It is bull  to defend sub par products especially when the safety of peoples lives are involved.

[Wytnucls]

One does wonder how these meters that don't meet their rating make it into the main stream market place. Bearing in mind false advertising is illegal and a lot of multimeter company's are responsible for this. To those who bash Dave in this video it is dam essential that these company's are held up and exposed for not making a product as advertised.

It is bull  to defend sub par products especially when the safety of peoples lives are involved.

You don't seem to understand how the system works.
Non-governmental IEC publishes electrical standards with occasional revisions. (IEC61010)
Revisions stipulate changes concerning input protection, but also include modifications of the testing procedures, with more stringent requirements to comply with the IEC CAT rating system.
Most countries then adopt those standards revisions as their own, from a specific date, with a grace period for manufacturers' and importers' compliance. (EN61010 for Europe, UL61010 for the US)
That grace period has expired in Europe (October 2013), but not necessarily in other countries (USA January 2018).
Some manufacturers re-submit their products (often with modifications) for independent testing, to confirm new standards compliance.
The meter Dave reviewed was first released under the previous standards, when HRC fuses were not a requirement and current range testing voltage was half of what it is now. A new version of that meter is available, with HRC fuses and revised PCB.
There is no sure way to know if a meter complies fully with regulations, unless it has gone through independent testing. In Europe, a CE marking is mandatory, with EN61010 compliance the responsibility of the manufacturer or in some cases, the importer.

[Fungus]

I don't give a damn who posted what, I was just curious where this was heading.

Well I care, not fighting just some people like to say that they were first with the revelation.

Maybe I didn't see your post, maybe I posted it independently. It happens.

[Yago]

I don't give a damn who posted what, I was just curious where this was heading.

Well I care, not fighting just some people like to say that they were first with the revelation.

Maybe I didn't see your post, maybe I posted it independently. It happens.

Actually I posted it first, it was about three years before the formation of this forum.
As I AM Spartacus!
:p

[Quarlo Klobrigney]

It's just that it is done with arrogance and then the quote from Fungus is:
"Not really. I looked at his posting history ( https://www.eevblog.com/forum/profile/?area=showposts;u=88216 ) and I can't see that he's ever posted anything related to an exploding multimeter. Certainly not in this thread."
I don't have a lot of posts only 50 or so, and most of those are for the secret ordering code. Fairly easy to find if you really looked. And with that, I'm done.

[Fungus]

I don't have a lot of posts only 50 or so, and most of those are for the secret ordering code. Fairly easy to find if you really looked. And with that, I'm done.

If you're accusing somebody of plagiarism, a simple reference to your original post will save a lot of confusion.

(because if they're innocent they'll have literally no idea what you're talking about)

[miguelvp]

Posting a link is hardly plagiarism

First hit to that link:
https://www.eevblog.com/forum/testgear/dangerous-multimeter-mastech-m890g-m890g2-(aka-dc-electronics-dc03)/msg386230/#msg386230

But really it doesn't matter as long as the message is conveyed and no one gives a .... who posted it first.

Giving credit to someone's work is one thing, but to a link that is in the public domain? that is a bit ridiculous.

[gildasd]

To get back on subject:

Is there a method to test the rating of a multimeter?
Lets say I'm a small company and I'm not sure of the rating of My Uni-T, Fluke, 5$ wonders (etc) and decide to sacrifice one with an incremental test to see how many amps are needed to blow the thing up in conditions I or my employees work in.
(Without killing the intern that is).
Why? Underwriter's stamp should suffice?
Yeah, but I might have special condition: inert gas, salty air water, hydrocarbon mix above UEL (etc) that are very specific.
(These conditions are pretty common in the maritime industry)
I'd rather burn a 400$ meter than blow the hand of an employee.
Dave did a test using a High Energy 4KV capacitor unit in episode 84.
But is that kind of "pulse" (no idea how to correctly name it) a reflection of  what happens in real life?

[Lightages]

There is no test you can do safe for you. If you want a meter that will withstand marine abuse then you probably want one that has an IP67 rating and probably one that is rated as intrinsically safe, such as the Fluke 28IIEX. Be prepared for sticker shock.

Additional:

The Fluke 27II is also IP67 and well suited for marine use. There is also the Amprobe HD160C which I find very interesting too: http://www.tequipment.net/AmprobeHD160C.html

CEM, and its rebrands like Extech EX series, has some IP67 meters too that are apparently properly rated and certified, if you get one that is properly built. There have been many reports here and on other sites of poor quality control.

[EEVblog]

You can buy insulation testing equipment. It costs more than many meters. Basically it generates very high energy pulses. You connect the DMM, stand back and see if it can survive its rated voltage/current.

It's more than that, it can be a destructive test. i.e. it has to "fail safe".

[VK3DRB]

Actually there was a high end Fluke handheld which had data recording features that someone bought at a previous workplace around 5 years ago. The meter had to go through a slow boot up sequence when powering up, but the real horrible thing was the continuity check. Often you had to hold the leads on for a second or two before it would beep . Sometimes it was quick. I suspect the microcontroller code used task polling to detect continuity. FAR worse that the UNIT-T piece of crap. A $10 meter was more usable for continuity. No-one wanted to use that meter except the bloke who bought it (to save face I suspect). The Fluke should never have been sold, and Fluke should have be ashamed for pushing such a crap product. I used an Agilent 34410A instead.

I am still a fanboy of the Fluke 179 . Possibly the best handheld meter ever. But to be honest, nothing beats the high end Agilent meters like the one in Dave's video if you want a bench multimeter .

[gildasd]

You can buy insulation testing equipment. It costs more than many meters. Basically it generates very high energy pulses. You connect the DMM, stand back and see if it can survive its rated voltage/current.

It's more than that, it can be a destructive test. i.e. it has to "fail safe".

If I get this, a simplified test (for real world application, not science) could be:
- Hook that insulation testing equipment up to a multimeter that set in the appropriate mode:
- Install in it's operating environment (lab simulation, or simply in real thing if not a danger), let it lie for 15 min (or the 2x the max time you spend in there).
- Start using high energy pulses from half it's rated capacity (if 500V, use 250v) with whatever Watts/Amps need be.
- Increment by 100V leaving 10minutes between pulse.
- See where she blows, let's say "X", and use X/2 as your max in that environment/usage.
Probably not perfect, but doable by almost anybody/any company.

[rsjsouza]

The Fluke should never have been sold, and Fluke should have be ashamed for pushing such a crap product.

Do you recall which model was it? Just curious...

I am still a fanboy of the Fluke 179 . Possibly the best handheld meter ever.

I really like mine as well. Built like a tank and absolute peace of mind when I use it on high power circuitry. More expensive? Yes, but for something that I expect will at least survive as much as my previous meter (25 years), that translates to only about ten dollars/year.

[Terabyte2007]

I am still a fanboy of the Fluke 179 . Possibly the best handheld meter ever. But to be honest, nothing beats the high end Agilent meters like the one in Dave's video if you want a bench multimeter .

I have the 34461A but was seriously considering the Fluke 8846A with 24ppm at .0024% accuracy it has a slight edge over the 34461A. BenchVue and the TFT trending display capabilities are what sold me.

[VK3DRB]

The Fluke should never have been sold, and Fluke should have be ashamed for pushing such a crap product.

Do you recall which model was it? Just curious...

I am still a fanboy of the Fluke 179 . Possibly the best handheld meter ever.

I really like mine as well. Built like a tank and absolute peace of mind when I use it on high power circuitry. More expensive? Yes, but for something that I expect will at least survive as much as my previous meter (25 years), that translates to only about ten dollars/year.

I can't recall the model, though it might have been the Fluke 287 or 289. Maybe the model was taken off the market because it was so lousy.

Yes, the 179 is expensive, but it is worth it. Whoever designed that meter deserved a medal. The specification alone makes it outstanding compared to most meters. The build quality is excellent too. Not to mention battery life.

Lower costs 179's are available from eBay occasionally. I bought one about 5 years ago as new from the USA (unwanted gift) for $US 155 delivered to my door in Australia. It is genuine, and I tested its accuracy and found it was be well within specifications. What really impressed me was it was new. Not a scratch or mark on it, complete with box and leads. New here is around $US 350 or so. Even then they are worth the money to anyone who wants to meter to provide faithful service for many years.

[G7PSK]

I wonder how many DMM would stand up to being tested with a Megger S1-1568, 15KV and will test insulation to 35 Tohms.

http://www.megger.com/eu/products/ProductDetails.php?ID=2382