Author Topic: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)  (Read 155869 times)

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Offline EEVblog

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EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« on: February 07, 2015, 01:50:53 am »
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

 

Offline mariush

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #1 on: February 07, 2015, 02:11:15 am »
The weird ass adapter looks like it has the classic European mains sockets (well, most of Europe)

Only viewed the first 6 minutes so far but it seems you're unfair comparing and saying it sucks because it doesn't match the metrahit which is 4 digit in cost.

agree with the fuse choice...

4:50 : you can't wiggle those round metal things once the case is closed, the case would press on the metal keeping it in place.



« Last Edit: February 07, 2015, 02:29:17 am by mariush »
 

Offline EEVblog

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #2 on: February 07, 2015, 02:28:18 am »
Only viewed the first 6 minutes so far but it seems you're unfair comparing and saying it sucks because it doesn't match the metrahit which is 4 digit in cost.

If a multimeter can measure power, then damn straight I'm disappointed if it can't measure that over all its ranges.
 

Offline iloveelectronics

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« Last Edit: February 07, 2015, 02:40:15 am by iloveelectronics »
My email address: franky @ 99centHobbies . com
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Offline Lightages

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #4 on: February 07, 2015, 02:43:13 am »
This was the first multimeter I posted about here in 2010. It arrived at 0.4% accuracy. After getting some "help"from Uni-T I got it working OK. If you want to know to see the schematic I have uploaded one. It appears that the UT71E is the worst deal amongst the UT7X series. There are some here who think the UT71D is a good deal. The UT71E is the same as the Voltcraft VC940, and the UT71D the Voltcraft VC960.

Uni-T has stepped up their game with their latest meters. The UT171X series, UT181, and the UT139C are much better for input protection.

It was because of my disappointment with the UT71E that I started down the rabbit hole of multimeter quality and safety.
 

Offline Smokey

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #5 on: February 07, 2015, 02:43:57 am »
Did you really actually buy that meter yourself like you implied in the video?  Are you saying you bought a piece of test gear from a company you know makes crap without even looking at the specs first?  Why would you even consider spending money on this if you know you already had far superior tools like the Gossen?  You couldn't get someone to give/loan you one for videos? 
 

Offline Chrisdlb

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #6 on: February 07, 2015, 03:15:09 am »
Irrefutable evidence that Uni-T metres are shit, provided by dave, but yet still for some reason, people try to defend them!  :palm:
 

Offline Lightages

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #7 on: February 07, 2015, 03:20:06 am »
Irrefutable evidence that Uni-T metres are shit, provided by dave, but yet still for some reason, people try to defend them!  :palm:

Irrefutable that the old models of Uni-T are almost all shit. They really have improved things on some new models.
 

Offline george graves

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #8 on: February 07, 2015, 03:32:36 am »
I'd expect a review of more then one Uni-T meter before claiming that all "Uni-T Meters Suck".  Sucks compared to what?  A meter costing 10x as much?  |O

I think the inner multimeter snob conosur in Dave came out a bit too much in this video. 

These are tools.  Tools cost money(that not everyone has).  Tools have limits.....knowing the limits of your tools is the more important thing.




« Last Edit: February 07, 2015, 03:40:00 am by george graves »
 

Offline alter Ratz

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #9 on: February 07, 2015, 03:52:20 am »
Hi all,

What I personally really hate about the UNI-T meters is that they are REALLY slow (not only continuity but also range switching). Has this gotten better with the new models?

Best regards,
Bernhard
 

Offline sakujo7

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #10 on: February 07, 2015, 04:50:48 am »
Putting "CAT IV 600V" on a meter that clearly cannot meet that spec is just... :wtf:. Being overly optimistic about accuracy is one thing, but you do NOT mess with safety ratings.

It's a shame, because some of their meters (eg. the 61E) work reasonably well for the price point for low-voltage only. (I own one and occasionally use it for this purpose).

A suggestion for anyone still buying one: scrape off the Cat III/IV labels.
 

Offline TMM

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #11 on: February 07, 2015, 04:56:40 am »
 few things to note:
-UT71C/D/E is only 0.025% on the 400mV range. It's 0.05% up to 400V. The 400mV range probably bypasses some of those trimmers because the input impedance is different also (2.5Gohm vs 10Mohm).
I've had a UT71D for 3+years and a Fluke 87V for 2+years and both of them have always (and still do) agree within 5 counts on DC.
-To be fair the screw hole via going through the current trace doesn't reduce the trace width too drastically because of the plating inside the via and the meter is only rated for 5A continuous anyway. 10A rating is <10seconds with 15minute cooldown.
-The datasheet linked on youtube is for the ES51922 instead of the ES51966 which is a 44000/440000 count meter chip http://www.cyrustek.com.tw/spec/ES51966.pdf
-See if you can get a true 40,000 counts of resolution on resistance or current out of the UT71 ;) (spoiler: there is some kind of lower res + averaging funny business going on).

It's not that bad for the price really. Terrible as an everyday meter, good cheap companion to something like a Fluke 87 for electronics work.



« Last Edit: February 07, 2015, 05:01:56 am by TMM »
 

Offline Nerull

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #12 on: February 07, 2015, 05:02:52 am »
"We've got ourselves a voltage reference, Maxim, If it's genuine." "I'm sure it is"

Why bother speculating it might not be genuine with one breath and then with the very next breath claim to be sure it is? What's going on?

Are you familiar with the term 'sarcasm'?

Quote
I don't personally care for the full-on shitcanning style you like using from time to time but I know it is popular.

It looks to me you started out with the intention of hammering the crap out of UNI-T and then as time went on you started to do a review and you got a bit more objective.

I'm no fanboy and if UNI-T claim some standard and then fail to meet it they deserve all the criticism you can heap on them. But for viewers like me who aren't intimately familiar with CAT ratings and PCB design to meet them it would be better if you toned down the noise and increased the explanation. The information IS there but you make it harder to distil it out.  The most useful part was when you started comparing with other examples of how things can be done better. A complete novice, who is more likely to consider a cheaper meter, would have an even harder time than I did filtering out the noise.

I kept wondering WHY you bought it in the first place. It sounded like you made a mistake and then wanted to throw a brick through UNI-T's front window.

The Uni-T pretends its rated for measurements directly on the outputs of a power transformer to a building, where there are no breakers to protect you and available current is north of 10000 amps (the limit for Class 3). If this meter were used on such a circuit improperly or experienced a spike it would quite literally explode in your hand and stands at least a half-decent chance of taking you with it. The rating is a complete lie, and if they're willing to lie about basic safety what else is wrong?
« Last Edit: February 07, 2015, 05:05:26 am by Nerull »
 

Offline feetwet

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #13 on: February 07, 2015, 05:12:05 am »
I just wanted to say the EE man is back. It's nice to see Dave back in his rare form. I thought the review of the Uni-T UT71E was spot on. Nice work Dave.  :-+

 

Offline gonzoid

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #14 on: February 07, 2015, 05:15:28 am »

Quote
"Well, it's not a fluke. It's... you know what I mean."
Perfect timing to post this video. Advertisement at its finest!!  :-DD :wtf:

What I personally really hate about the UNI-T meters is that they are REALLY slow (not only continuity but also range switching). Has this gotten better with the new models?
If you happen to have one of the UT71 series, you can press and hold the blue button while powering on the meter to enable its 4000 counts mode, which is way faster.
« Last Edit: February 07, 2015, 05:36:51 am by gonzoid »
 

Offline DanielS

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #15 on: February 07, 2015, 05:39:38 am »
Putting "CAT IV 600V" on a meter that clearly cannot meet that spec is just... :wtf:. Being overly optimistic about accuracy is one thing, but you do NOT mess with safety ratings.
And that would likely be why Uni-T has no official distributors and meters are only available through third-party sellers on places like Amazon, Craigslist, eBay, etc.

If Uni-T had official ties outside China, that would expose them to lawsuits for wrongful death or injuries attributable to failure to meet their safety rating claims if there has been any.
« Last Edit: February 07, 2015, 06:13:33 am by DanielS »
 

Offline TMM

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #16 on: February 07, 2015, 05:46:56 am »
If Uni-T had official ties outside China, that would expose them to lawsuits for wrongful death or injuries attributable to failure to meet their safety rating claims if there has been any.
Well they sort of do. Uni-T meters are sold under the "Tenma" brand through Farnell/Element14 for example. If anyone knows if the Tenma variants are built safer I'd be interested to know.
 

Offline gonzoid

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #17 on: February 07, 2015, 06:15:43 am »
Well they sort of do. Uni-T meters are sold under the "Tenma" brand through Farnell/Element14 for example. If anyone knows if the Tenma variants are built safer I'd be interested to know.
Appart for the case color, they don't seem to be any different according to the photos on http://sigrok.org/wiki/UNI-T_UT71x_series
 

Offline TMM

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #18 on: February 07, 2015, 06:20:00 am »
I just don't get the pricing on these product's, either the middle men are
making a truck load [...]
And the same can't be said for particular Fluke and Agilent products? It's worth whatever people are prepared to pay for it, and people do buy them so what's the issue?

The UT71D which is basically what Dave reviewed minus the power measurement capability can be found for ~US$130 including international shipping. That doesn't seem like a half bad deal to me for a ~0.05% meter with USB datalogging and 10,000 points memory.
« Last Edit: February 07, 2015, 06:26:13 am by TMM »
 

Offline DanielS

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #19 on: February 07, 2015, 06:30:24 am »
Well they sort of do. Uni-T meters are sold under the "Tenma" brand through Farnell/Element14 for example. If anyone knows if the Tenma variants are built safer I'd be interested to know.
I know there are variants of the UT61E which actually have MOVs. My UT61E is one of the no-MOV variant.

I just don't get the pricing on these product's, either the middle men are making a truck load [...]
And the same can't be said for particular Fluke and Agilent products?
At least, Fluke and Agilent are not carrying fake safety ratings.

Pop the back on most Uni-T multimeters and you quickly realize that safety ratings on them are blatantly criminally fake, which is a shame when minor PCB layout changes are often all that would be required to make them considerably safer - along with proper fuses which many models lack.

The lack of precision parts in something that claims to be a precision instrument is not exactly reassuring either, even if it has been trimmed into the next time zone to bring it somewhere within specs.
 

Offline TMM

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #20 on: February 07, 2015, 06:58:01 am »
Pop the back on most Uni-T multimeters and you quickly realize that safety ratings on them are blatantly criminally fake, which is a shame when minor PCB layout changes are often all that would be required to make them considerably safer - along with proper fuses which many models lack.
While I hope no one buys one of these meters hoping to use it on high energy circuits, you'd be kidding yourself to think that Uni-T are the only ones who put dubious ratings on their meters. Also depending where you live it may not be illegal to sell a meter that displays a CAT rating but has not been compliance tested.

Input protection is a non-issue for people who only plan to dick around on the bench with low power electronics anyway so many of us are willing to overlook the safety claims because Uni-T meters present a unique combination of features/value that very few others provide.
 

Offline bitshape

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #21 on: February 07, 2015, 07:02:28 am »
Thanks for the nice Ranteview Dave!  :clap:


And really; buying a decent multimeter is not impossible, even for a Fluke in fluking-expensive Europe:

I bought a Fluke 287 for €270,- (incl.vat), and it was almost never used before and even with the original (half-empty) batteries in it. After buying I filled it with a set of rechargeable Eneloop-AA and it is still my best portable meter on the bench.
And some time later an new and unused 'open box' Fluke 28II for €200,- (incl.vat), and seriously, nothing wrong with it. This meter has now got a fresh set of Energizer Lithium-AA's for the long run. :-+

Thus it is possible for everyone to buy something safe & decent (read: not a €190,-* Uni-Trash) for a 'decent' price, only if you are patient and regularly look on some closing-business-auction-sales and your local/online marketplace.

* Uni-T UT71E  incl.vat & delivery
« Last Edit: February 07, 2015, 07:41:49 am by bitshape »
 

Offline EEVblog

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #22 on: February 07, 2015, 08:16:00 am »
"We've got ourselves a voltage reference, Maxim, If it's genuine." "I'm sure it is"
Why bother speculating it might not be genuine with one breath and then with the very next breath claim to be sure it is? What's going on?

Welcome to non-scripted off-the-cuff video blog. I press record and something comes out.

Quote
I don't personally care for the full-on shitcanning style you like using from time to time but I know it is popular.

IIRC you don't seem to care for much of what I do at all, you seem to be always criticising  ::)

Quote
It looks to me you started out with the intention of hammering the crap out of UNI-T

You are wrong.
I was hoping this meter with it's rare power measurement function would actually be OK.

Quote
I'm no fanboy and if UNI-T claim some standard and then fail to meet it they deserve all the criticism you can heap on them. But for viewers like me who aren't intimately familiar with CAT ratings and PCB design to meet them it would be better if you toned down the noise and increased the explanation.

I've done videos on this stuff before, go watch them, I can't repeat everything in every single video every single time.

Quote
I kept wondering WHY you bought it in the first place. It sounded like you made a mistake and then wanted to throw a brick through UNI-T's front window.

Stated above.
 

Offline EEVblog

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #23 on: February 07, 2015, 08:20:10 am »
I'd expect a review of more then one Uni-T meter before claiming that all "Uni-T Meters Suck".

I have yet to find a single Uni-T meter that is well engineered and manufactured.
Prove me wrong, please.
 

Offline EEVblog

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #24 on: February 07, 2015, 08:28:50 am »
Tools have limits.....knowing the limits of your tools is the more important thing.

What do you say about tools that claim to have a particular safety rating on the front, but fail to meet that spec?
By your reckoning everyone is supposed to open their meter and critically analyse the design to see if it meets the specs  :palm:
 

Offline EEVblog

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #25 on: February 07, 2015, 08:33:42 am »
Did you really actually buy that meter yourself like you implied in the video?

Yes.

Quote
Are you saying you bought a piece of test gear from a company you know makes crap without even looking at the specs first?

Not in minute detail, no.
I thought I saw evidence it might be a goer, it wasn't.

Quote
Why would you even consider spending money on this if you know you already had far superior tools like the Gossen?

In case you weren't aware, I run an electronics video blog. One of things I do is test equipment reviews.
There is also another reason which I won't elaborate on.

Quote
You couldn't get someone to give/loan you one for videos?

Maybe, but it was a spur of the moment thing.
 

Offline Wytnucls

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #26 on: February 07, 2015, 08:40:58 am »
While Dave's review was entertaining, fairness wasn't high up on the agenda. Dave couldn't even find the precision resistor network on a very simple board design.
Nobody will dispute the very basic input protection and the slow continuity test on those meters. If you can live with that, the meter has some redeeming aspects. It offers a host of features for the electronics hobbyist at a very affordable price.
The Cyrustek 40,000 count dual slope ADC, while not the fastest, is pretty good (also used in the FLIR meter) and drift, which I monitored over 2 years, is minimal. Calibration can be done through the RS232 with connection to calibrator or, cheaply, manually with the trimpots. I haven't had to adjust mine yet, unlike the 61E.
While I also own Fluke and Gossen DMMs, I value my UNI-T meters for specific tasks, like datalogging and peak detection, for instance.
Here is my 71D review, if you haven't seen it yet: https://www.eevblog.com/forum/testgear/uni-t-ut71d-review/
« Last Edit: February 07, 2015, 04:03:19 pm by Wytnucls »
 

Offline Chupacabras

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #27 on: February 07, 2015, 08:41:06 am »
The weird ass adapter looks like it has the classic European mains sockets (well, most of Europe)

Well, one of the good things about this meter is that it has PROPER mains adapter. Not that weird overseas one...
Cheers from Europe ;)

Actually, Dave could do some video blog rant about pros and cons of mains sockets from different parts of the world.
 

Offline TMM

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #28 on: February 07, 2015, 08:47:53 am »
While Dave's review was entertaining, fairness wasn't high up on the agenda.
Have to say i agree...

Next week on EEVBlog, "Why Fluke multimeters SUCK"

"Look at that offset on the current range, what a flaming pile of turd!"
 

Offline george graves

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #29 on: February 07, 2015, 08:54:10 am »
What do you say about tools that claim to have a particular safety rating on the front, but fail to meet that spec?
By your reckoning everyone is supposed to open their meter and critically analyse the design to see if it meets the specs  :palm:

A fool and his life are soon parted with?  Darwin award?  Who in their right mind would work with +300V from a Chinese multimeter?  Granted, in the US, we only really have 120, so for us, it's really not much of an issue.   :bullshit:

I have yet to find a single Uni-T meter that is well engineered and manufactured.
Prove me wrong, please.

I can't.  You prove ME wrong.  ;)  What Uni-T meters have you looked at?  You asserted that "they are all crap".  I was merely asking "Ok back that statement up!!?!?"

Dave, Uni-T has improved in their recent releases. Have a look at the newer 139, 171 and 181 series, they are built much better (to my untrained eyes anyway):

https://www.eevblog.com/forum/testgear/new-trms-uni-t-ut139c-dmm-is-available-now/msg289221/#msg289221
https://www.eevblog.com/forum/testgear/uni-t-ut171a-pictures-and-first-impressions/
https://www.eevblog.com/forum/testgear/uni-t-ut171b-teardown/
https://www.eevblog.com/forum/testgear/uni-t-ut181a-pictures/

They really have improved things on some new models.





« Last Edit: February 07, 2015, 09:09:12 am by george graves »
 

Offline Barny

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #30 on: February 07, 2015, 09:06:49 am »
Actually, Dave could do some video blog rant about pros and cons of mains sockets from different parts of the world.
Thats a good idea.

@Dave:
I think you have to take the this estimating-iron to your friend with the special test-gear like the Fluke in your intro video.

@George Grave
If its about safety-rating it had to meet its specs.

If not, its crap.
There is no excuse like in Kindergarten: "But other multimeter does ist too."

A fool and his life are soon parted with?  Darwin award?  Who in their right mind would work with +300V from a Chinese multimeter?  Granted, in the US, we only really have 120, so for us, it's really not much of an issue.   :bullshit:
Dont take your crap powerlines as an excuse.
Have you thought about oscilatorcircuits?
You'll get several 1000V out of an 1,5V batery.


The only positive thing i've seen is a little bit of blast-protection of the case when it blows up
« Last Edit: February 07, 2015, 09:12:54 am by Barny »
 

Offline EEVblog

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #31 on: February 07, 2015, 09:10:06 am »
While Dave's review was entertaining, fairness wasn't high up on the agenda. Dave couldn't even find the precision resistor network on a very simple board design.

Because it's not there.
Please point out where the precision ceramic hybrid resistor network typically found in such accuracy class instruments actually is. Perhaps I did miss it, in which case please show it to me.
 

Offline TMM

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #32 on: February 07, 2015, 09:11:24 am »
Dont take your crap powerlines as an excuse.
Have you thought about oscilatorcircuits?
You'll get several 1000V out of an 1,5V batery.
It isn't exactly going to make a meter with M205 glass fuses explode like a grenade though is it? Worst case bzzt and the meter stops working.
 

Offline george graves

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #33 on: February 07, 2015, 09:14:33 am »
@Dave:
I think you have to take the this estimating-iron to your friend with the special test-gear like the Fluke in your intro video.


That I would like to see that.  See if it can withstand 600v.



Dont take your crap powerlines as an excuse.
Have you thought about oscilatorcircuits?
You'll get several 1000V out of an 1,5V batery.

Our crappy power line?  You mean the one powered by freedom?   :)  :box:

Yea, I know you could get a +1000V volts out of a AA battery, but there would never be enough energy there, right?

Offline mikeselectricstuff

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #34 on: February 07, 2015, 09:17:01 am »
No reason you can't have trimmers on a high accuracy bit of kit, as long as their adjustment range is properly limited with external resistors , e.g. +/=0.05% adjust range  on a 0.25% spec
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Offline Wytnucls

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #35 on: February 07, 2015, 09:18:05 am »
While Dave's review was entertaining, fairness wasn't high up on the agenda. Dave couldn't even find the precision resistor network on a very simple board design.

Because it's not there.
Please point out where the precision ceramic hybrid resistor network typically found in such accuracy class instruments actually is. Perhaps I did miss it, in which case please show it to me.
8 Precision metal film resistors 1W TCA5C6 (4x2.5M and 1M11, 101K, 10K1, 1K01) (0.05% resistance tolerance and 10ppm/C)
Lift the skirt on the metal shield can.
The meter has lots of issues, but voltage accuracy is not one of them.

« Last Edit: February 07, 2015, 09:23:33 am by Wytnucls »
 

Offline EEVblog

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #36 on: February 07, 2015, 09:18:13 am »
A fool and his life are soon parted with?  Darwin award?  Who in their right mind would work with +300V from a Chinese multimeter?  Granted, in the US, we only really have 120, so for us, it's really not much of an issue.   :bullshit:

It seems I have to correct you almost every time you speak George  :palm:
It's not about what line voltage you use, it's about the energy capacity behind it, and the ability for high energy overvoltage transients to happen.
If you knew anything about mulitmeter protection and CAT rating then you would have known that. Clearly, you don't.

I can't.

Thanks for admitting that.

Quote
You prove ME wrong.  ;) 

I don't have to because I don't give a toss about you say.
 

Offline Huluvu

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #37 on: February 07, 2015, 09:21:15 am »
As far as I understood from the cut outs of the Standard EN 61010-1 the Cat Ratings before 2004 could have had exclusions for the Ratings.
It looks like the valid Standard before 2004 (released in 1995) you can exclude everything you want from the requirements.
As an example this would mean that you may only validated Volts AC measurement on your Multimeter and exclude every other Measuring part from it.
--> using for e.g. 250V Fuses instead of the required 600V or 1000V Fuses.

For sure this would not explain why Uni-T can still produce and distribute Meters like Dave's Version to the Market.
Even it would not explain why there is not the expected creepage and clearance on the Volts Input section ....

It would be interesting if there is any different on the current selling Europe Versions which are directly purchased from Europe Market.
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Offline EEVblog

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #38 on: February 07, 2015, 09:23:17 am »
8 Precision metal film resistors 1W TCA5C6 (4x2.5M and 1M11, 101K, 10K1, 1K01) (0.05% resistance tolerance and 10ppm/C)
Lift the skirt on the metal shield can.


There are 4 x 1W axial metal film resistor under that can that also contains trimmers? Doesn't look like there is enough room to me. And based on the underside photo of pins protruding, they would have to be mounted vertically. 1W resistors are not small.
But ok, if you say so, I'll have a look next time I'm in the lab.
« Last Edit: February 07, 2015, 09:28:56 am by EEVblog »
 

Offline Barny

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #39 on: February 07, 2015, 09:24:10 am »
Dont take your crap powerlines as an excuse.
Have you thought about oscilatorcircuits?
You'll get several 1000V out of an 1,5V batery.
It isn't exactly going to make a meter with M205 glass fuses explode like a grenade though is it? Worst case bzzt and the meter stops working.
That was only an example, because he thought that 115V/120V are on the save site when he uses this meters.

PS:
If the involved capacitor is big enough, the bzzt will get a nice booom.

If I remember right, the multimeter which get blown in daves intro video was with the usage of the energy of an AA Cell.

@Gorge:
I knew.
Your powerlines runns with feedom and hope instead of electricity.
And you deliver your freedom with 700 bullets per minute to the whole word.
« Last Edit: February 07, 2015, 09:28:55 am by Barny »
 

Offline Wytnucls

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #40 on: February 07, 2015, 09:25:59 am »
Don't need to warm up the iron, I have a picture:
I'll grant you it is a crude design, but it seems to work.
 

Offline EEVblog

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #41 on: February 07, 2015, 09:30:41 am »
Don't need to warm up the iron, I have a picture:

That is not the same model nor layout as the UT71E.
 

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #42 on: February 07, 2015, 09:31:18 am »
I don't get into all this stuff, fascinating watching all the views .pictured is my multimeter which I've owned from New,low count so what I got it cal checked at work,passed straight off perfect measurements,the cal dept want me to sell it to them "No Chance". Used daily how about these bit's of quality Dave :-+
 

Offline EEVblog

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #43 on: February 07, 2015, 09:39:27 am »
While Dave's review was entertaining, fairness wasn't high up on the agenda.
Have to say i agree...
Next week on EEVBlog, "Why Fluke multimeters SUCK"

I gave the UT71E a fair go by actually getting it and doing a review and teardown. But review not going to happen now, I won't waste my time.
It's not my fault that it failed to deliver. Which is something that Uni-T does time and time again seemingly without fail.
My comment about them sucking is based on evidence, in case you missed it.
Just because some people don't like me pointing it out doesn't mean I'm not being fair.
Unfair would be to not review any more Uni-T meters because they have always failed to impress. But I didn't, so once against, evidence that I gave them a fair go by actually doing this.
 

Offline Wytnucls

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #44 on: February 07, 2015, 09:41:45 am »
Don't need to warm up the iron, I have a picture:

That is not the same model nor layout as the UT71E.
That's a 71B, AFAIK, they are all the same under that metal can (71D for sure). I don't own the 71E, so check when you have time, but I'd be very surprised if they are not there. The meter wouldn't work without them.
 

Offline EEVblog

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #45 on: February 07, 2015, 09:45:15 am »
That's a 71B, AFAIK, they are all the same under that metal can (71D for sure). I don't own the 71E, so check when you have time, but I'd be very surprised if they are not there. The meter wouldn't work without them.

You can see on the photo I posted they are not the same. Clearly less parts and huge isolation slots on the UT71E.
Perhaps they have moved to SMD parts though, I have to open the can.
 

Offline Wytnucls

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #46 on: February 07, 2015, 09:53:56 am »
Perhaps. You have one of the latest board revisions with 'improved' clearances and space for HRC fuses. I doubt it though. Let us know later.
 

Offline meerweten

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #47 on: February 07, 2015, 09:56:15 am »
seems like ut updated their design of the ut61 model (i recently replaced my old dvm870 with the ut61D)

in my case there are crapy chinees HRC fuses :p , can't remembet the voltage rating on them

do i claim its a good meter?
For my use and budget it might be, still want to have a fluke, just can't afford it :'(
Meerweten, Want meten is Weten
 

Offline hamdi.tn

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #48 on: February 07, 2015, 10:09:32 am »
this way clearly a rant , can't say this is an objective review , we all know it's cheap product that do the job for low end application, as poor engineering, i think who ever built this is capable of designing a good one and uni-t is capable of manufacturing a high level multimeter BUT if everyone do that , no one will be able to buy a 15$ meter working for 4 years now.
so yeah they suck but ...they suck for a purpose.

 i think the spring is connected to the case shielding (not those for the buzzer) , so nothing wrong if it touch the shielding metal mounted in pcb.
 

Offline TMM

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #49 on: February 07, 2015, 10:11:13 am »
fwiw, the 71D I have (purchased early 2012) has through-hole resistors like Wytnucls' visible through the perforations in the can.


While Dave's review was entertaining, fairness wasn't high up on the agenda.
Have to say i agree...
Next week on EEVBlog, "Why Fluke multimeters SUCK"

I gave the UT71E a fair go by actually getting it and doing a review and teardown. But review not going to happen now, I won't waste my time.
I already posted this to youtube, but i will repost the same here again. You used statements like "out of spec according to the agilent" and then "juuuuust going to squeeze in" when both times it was well within the claimed % of reading + counts claimed in the Uni-T's manual. You also claimed that "0.3%+8" spec for resistance measurement was poor, when a Fluke 87V is "0.2%+10" in 20000 count mode and costs significantly more. This makes your review biased imo. An unbiased review would have checked that the multimeter was within specification and moved on without making derogatory comments about it. The claimed specs of the UT71 are exceedingly good for the asking price and even you were able to confirm that it meets them out of the box.

The spec for the Amps range on a Fluke 87V is 0.2%+20 and as i have shown mine is 15 counts out with the inputs shorted (or open, makes no difference). It was like this the day i took it out of the box brand new. That makes it closer to being out of it's claimed spec than the Uni-T you tested was. Not every meter is going to be "0.0%+0" out of the box and Fluke is no exception so don't start moaning about a Uni-T that is 10 counts out when the claimed spec is up to 25 counts out.

Your claims that the meter can't have long term stability because it uses trimmer pots are also unfounded rumour unless you have tested it yourself or can point us to a reputable source that has characterised the drift of this particular multimeter, or has data on the expected drift of the trimmers/components used and calculates the overall expected drift with the circuit implementation that Uni-T has used.
« Last Edit: February 07, 2015, 10:36:31 am by TMM »
 

Offline miguelvp

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #50 on: February 07, 2015, 10:21:34 am »
I got my UT71B for just $35 at clearance from mortoncontrols, I never planned to use it for anything other than my little projects and for that price and 20000 counts it suits my needs.

I knew from the get go that the CAT ratings where not to be trusted but for the price and because I didn't want to spend too much and get something better than my crappier GB GDT-200A and adding data logging and everything else for that price it was on par of what I wanted for my under 24V measurement needs.

My biggest complain for my purposes is that the volume is quite high and if I disable the buzzer then it takes away the (slow) continuity test sound, other than that I'm happy with it for the discounted price, if it was the full price (around $100+) then no way I would have gotten it.



« Last Edit: February 07, 2015, 10:23:30 am by miguelvp »
 

Offline 0b01010011

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #51 on: February 07, 2015, 10:35:07 am »
If Uni-T had official ties outside China, that would expose them to lawsuits for wrongful death or injuries attributable to failure to meet their safety rating claims if there has been any.
Well they sort of do. Uni-T meters are sold under the "Tenma" brand through Farnell/Element14 for example. If anyone knows if the Tenma variants are built safer I'd be interested to know.
I have a Tenma 72-7730a, 20000 count (UT71B equivalent?) bought from Farnell Australia, and this has the much larger ceramic HRC fuses - similar to the Brymen meter Dave showed.  If anyone's interested in pictures I'm happy to try and get some sorted tomorrow.
 

Offline gonzoid

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #52 on: February 07, 2015, 10:37:56 am »
seems like ut updated their design of the ut61 model (i recently replaced my old dvm870 with the ut61D)
Interestingly enough, their new catalog (here) pretends both the UT61 and UT71 series are compliant with CAT.III 1000V and CAT.IV 600V ratings (specified by UL 61010-1, EN 61010-1, EN 61010-2-030 and EN 61326-1), but only the UT61 page is displaying logos from ETL/Intertek and TÜV/GS, implying only those models may have been approved.
« Last Edit: February 07, 2015, 10:45:02 am by gonzoid »
 

Offline open loop

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #53 on: February 07, 2015, 10:46:06 am »
Dave,

We have the Tenma branded version of these meters at Work, don't ask why - long story. Next time you are in the lab check out the battery consumption of these meters and then do a Blab rant about the battery consumption.

These meters are not terrible but not great either, ok if you are doing low energy work. (Next breath) I like to see your mains on the "ohms range" test.



 

Offline george graves

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #54 on: February 07, 2015, 10:58:49 am »
OK.  I'll trust your knowledge Dave.  You know a TON more then I do.  Absolutely, 100%.  Done and done. Never questions that. You win.   |O

But, "What Uni-T meters have you looked at?  You asserted that "they are all crap".  I was merely asking "Ok back that statement up!!?!?"

What other Uni-T meters have you had hands on with?  Fair question.  NO?

I'm betting that if you did another multimeter round up, that was up-to-date with the times, that a UNI-T would be a front runner in the $100-$150 range.  no?

For me....as a "amateur" I think I'm in a nice spot.  A 87-5 that I totally trust, and two UNI-T UT-61E's, and a 3478A.  An ebay DMM voltage reference standard.

I'm NOT an Uni-T fan boy - far from it.  I would gladly trade them in for something better.  But as a 2nd, 3rd, 4th meter, they are awesome.

Personally, I think what I have is over kill for 99.9% of people.  What am I missing?  We can't all have voltage standards and current sources.  You missed the point about price vs performance on this review IMHO.

There are a ton of people that are starting out, and need a decent meter, and will never measure +300 volts.  So, perhaps, a mention of that in the review would be warranted?



« Last Edit: February 07, 2015, 11:12:22 am by george graves »
 

Offline fubar.gr

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #55 on: February 07, 2015, 10:59:20 am »
My 71E has a different 10A shunt:


Offline Wytnucls

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #56 on: February 07, 2015, 11:03:39 am »
Tenma (Element14) sells the UNI-T UT71B and 71D under their brand. The meters come with 1000V HRC fuses to comply with the latest European safety regulations. (No independent testing AFAIK)
It would be interesting to examine the PCB to see if MOVs and PTCs have been installed.
Battery consumption is average (7mA) and should give 100hrs of normal use.
Mains on the Ohm's range has been done before. No drama, the meter has 1000V crowbar circuits on the relevant ranges.
 

Offline PeterL

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #57 on: February 07, 2015, 11:04:54 am »
I really can't understand how people can be so forgiving about this CAT-rating lie on meters like these. Sure most of the time safety is not an issue because of the nature of the circuits we are probing.
But if you buy you're meter for those circuits, you would be happy with a meter that said 'Not CAT rated!!'

Now for the meter reviewed here I think it's even worse, as it's unique selling point is meauring Watt's, not microWatt's, not milliWatt's but Watt's. They even provide a nice adapter encouraging you to hook it up to 230V mains. Also the price is high enough that you would expect some level of quality imho.

And about this being a Chinese meter, well WE know, but not everyone does. Uni-T sure doesn't sound Chinese to me, and it looks like a decent western product to.

But all that still doesn't matter. It says CAT-rated, so it should be CAT-rated. And if anyone could just put a CAT rating on their device, well than this whole rating is just worthless, as we simply cannot thrust this. I think that's something the entire sector should care about.
 

Offline Owen

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #58 on: February 07, 2015, 11:13:18 am »
Can someone explain why Brymen is putting a 10 A fuse @ 600V(ac) in a dmm that's rated for 8 A and 1000 V CATII? And why is Brymen doing this on the mA range (620 mA @500V), too?
 

Offline rolycat

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #59 on: February 07, 2015, 11:16:22 am »
The "improved safety" on the UT61 series largely seems to consist of fitting those 250V ceramic fuses.

As can be seen in Dave's video, they are marked 'BS1362', which is the British Standard for the fuses fitted to all UK mains plugs. Uni-T use them because they are manufactured in the millions, and are consequently very cheap. They are supposed to be HRC fuses, but there are a lot of dangerous fakes around these days. Example .
 

Offline Wytnucls

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #60 on: February 07, 2015, 11:20:47 am »
No, there is a GS approved version of the UT61 with proper HRC fuses and a lower CAT rating.
 

Offline mikeselectricstuff

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #61 on: February 07, 2015, 11:21:57 am »
It wouldn't be half as bad if they were just honest about the safety ratings- most people just don't need CatIV, but manufacturers seem obsessed with a "me-too" game of dishonestly copying competitors' specs and markings.
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Offline gonzoid

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #62 on: February 07, 2015, 11:22:23 am »
Tenma (Element14) sells the UNI-T UT71B and 71D under their brand. The meters come with 1000V HRC fuses to comply with the latest European safety regulations. (No independent testing AFAIK)
It would be interesting to examine the PCB to see if MOVs and PTCs have been installed.
I have a Tenma 72-7730a, 20000 count (UT71B equivalent?) bought from Farnell Australia, and this has the much larger ceramic HRC fuses - similar to the Brymen meter Dave showed.  If anyone's interested in pictures I'm happy to try and get some sorted tomorrow.
This meter is documented on the sigrok wiki: http://sigrok.org/wiki/Tenma_72-7730
A PCB revision from 2005 is pictured, it has minimum protection with only glass fuses, one PTC and one unpopulated location for MOV/GDT.
Show us some pictures, the more documented revisions, the better!  ;)


Calibration can be done through the RS232 connection or, cheaply, manually with the trimpots. I haven't had to adjust mine yet, unlike the 61E.
[...]
Here is my 71D review, if you haven't seen it yet: https://www.eevblog.com/forum/testgear/uni-t-ut71d-review/
I've quickly re-read your thorough review, but cannot find any mention of a calibration procedure through RS232. You meant the "hidden menu" procedure, right? ???
 

Offline jeremy

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #63 on: February 07, 2015, 11:25:55 am »
Um, how has no-one noticed the trace going nowhere? 5:44 in the video. Unless this board has plugged vias, which I seriously doubt. Or my eyes are deceiving me, which is more likely.

It's also visible in other peoples pictures in this thread.
 

Offline Wytnucls

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #64 on: February 07, 2015, 11:28:55 am »
I'm going by the Tenma multimeter manual, which mentions the 1000V fuses ratings and dimensions. Opening up a recent meter is the only way to find out for sure.
There is no menu as such for calibration. Just a calibration mode for the meter and a published paper procedure, with a calibrator hooked up.
In fact, now that I think about it, the calibration procedure doesn't need the RS232 connection which is not bi-directional. The software is in the meter.
« Last Edit: February 07, 2015, 11:40:14 am by Wytnucls »
 

Offline Pentium100

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #65 on: February 07, 2015, 11:29:53 am »
Different price categories, different capabilities. I cannot afford a $1000 multimeter and I do not need one (I'd rather buy a function generator). I do not need the 0.001% accuracy either. If I measure the B+ voltage of a radio and get 280V when the spec is 275V I will consider it OK and move to other areas to try to find the fault.

If I ever buy a more expensive meter than my current one, it will have to be able to measure AC voltage at up to 30kHz (to make tape deck calibration easier).

And yes, I do sometimes stick my not-sure-if-really-rated meter to mains to measure voltage. Though if I am repairing a switching power supply (like a PC PSU) I use a 2kVA isolation transformer and my Rigol DS1052E scope.

As for safety - I'd think that robbing a bank to buy the real CAT rated meter is way more dangerous than using the cheap meter and not robbing anyone.

I really can't understand how people can be so forgiving about this CAT-rating lie on meters like these.
Because it does not really matter to me, the meter can say CAT6 rated and I wouldn't really care. OTOH, if the spec said that AC voltage measurement frequency response is up to 30kHz and in reality it was 1kHz I would not be happy at all.
 

Offline Wytnucls

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #66 on: February 07, 2015, 11:42:51 am »
Um, how has no-one noticed the trace going nowhere? 5:44 in the video. Unless this board has plugged vias, which I seriously doubt. Or my eyes are deceiving me, which is more likely.

It's also visible in other peoples pictures in this thread.
Probably an isolation trace, but I'll let Dave answer that one. (The trace goes to ground with a via)
« Last Edit: February 07, 2015, 11:48:05 am by Wytnucls »
 

Offline Wytnucls

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #67 on: February 07, 2015, 11:54:05 am »
It wouldn't be half as bad if they were just honest about the safety ratings- most people just don't need CatIV, but manufacturers seem obsessed with a "me-too" game of dishonestly copying competitors' specs and markings.
Things are changing for the better, UNI-T and CEM are having most of their meters sent for independent testing nowadays. I suspect that the UT71s will be discontinued shortly, with safer meters having been released recently.
 

Offline electr_peter

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #68 on: February 07, 2015, 11:58:13 am »
Mains adapter is suited only for EU, but it is incredibly useful. It is actually very difficult (in practice) to quickly and safely rewire mains plug for both voltage and current measurements with any multimeter. It is possible to have one time setup with alligator clips, but it is kind of annoying and tricky to do so. I have made special adapter box just for that.
However, UT71E accuracy and resolution are only marginally better than simple cheap (~10-20€) mains power adapter - so what is the point of power measurement feature? It is useful only for high power AC and DC circuits, not for electronic circuits or battery drain measurements.

Blatant lie on CAT ratings is not excusable. While safety aspect for some forum users is not that important, you have to remember why CAT ratings were instituted at all. If meter in I or V mode is put on mains, internal low resistance arc can occur (both from blown glass fuse or arc-over) resulting in massive currents flowing through leads -> heating+fire+explosion+flying molten metal -> not fun at all. It is absolutely non obvious that this could happen ("Hey, I just going to check the voltage") and it is somewhat rare/exotic/unexpected event, so this safety issue is often neglected.

Some meters from UNI-T have good value for money. UT71E does not seem to be in that category in my opinion.
 

Offline PeterL

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #69 on: February 07, 2015, 12:07:32 pm »
I cannot afford a $1000 multimeter and I do not need one
I never said you had to spend $1000 on a multimeter. In fact, I don't spend that much on a meter either.

And I think I already stated in other words that we do not all need a meter with high CAT ratings.

I just think just like Mike said it would be a lot better if the meter didn't have these CAT III/IV ratings on it.

And again, this particulair meter just shout's "Connect me to a mains outlet" and "Let's measure the current consumption of you're vacuumcleaner, or other high power and/or inductive device". Lying about a CAT rating feels like horribly bad to me here.
 

Offline Yago

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #70 on: February 07, 2015, 12:17:37 pm »
The cat rating lies are unforgivable.
For people that say "it's OK, I don't use it on high energy circuits", well you know, that too is inexcusable too IMVHO.
Just because you are informed (and choose to forgive) uninformed users are at risk, and defending this company is putting more and more lives at risk.
I care more for my fellow man that anyone's profit margin.

Now, having variants on meters, some that may and some that may not meet cat ratings may even make this situation worse.
We all know that print is easier to forge/achieve that manufacture of good quality, and again it clouds this issue with the uninformed.

Stop with cognitive bias, and stop with selfism "I'm alright Jack" BS.
This company should be nailed to the wall.
I noticed that Maplin in UK sells UnitT meters, wonder if all these meet their cat ratings:
http://www.maplin.co.uk/c/components/component-testers/multimeters#Brand:Uni-Trend&sort=&page=1&productsPerPage=12
 

Online SilverSolder

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #71 on: February 07, 2015, 12:24:55 pm »
Lying about the CAT rating is a big mistake by Uni-T, even if the meters work fine otherwise.

It is like a car manufacturer lying about having crash tested their product.  Not really acceptable, is it?




 

Offline Wytnucls

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #72 on: February 07, 2015, 12:40:18 pm »
Maplin, as an importer, is responsible for making sure their recent meters comply with the latest IEC regulations. Old stocks are exempted for a while.
 

Offline Yago

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #73 on: February 07, 2015, 12:45:45 pm »
Maplin, as an importer, is responsible for making sure their recent meters comply with the latest IEC regulations. Old stocks are exempted for a while.

Thanks Wytnucls.
So that could be another example of this dangerous shite escaping onto the market through ambiguity and profiteering.
 

Offline Wytnucls

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #74 on: February 07, 2015, 12:52:53 pm »
Absolutely. There is a reporting system in Europe to counter the practice. Flawed products have to be removed from the market. Not sure about subsequent fines. (RAPEX)
« Last Edit: February 07, 2015, 01:20:10 pm by Wytnucls »
 

Offline Yago

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #75 on: February 07, 2015, 12:57:57 pm »
Absolutely. There is a reporting system in Europe to counter the practice. Flawed products have to be removed from the market. Not sure about fines.

Bet Maplin wouldn't agree to open up a meter and see what's inside!
 

Offline zapta

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #76 on: February 07, 2015, 01:00:29 pm »
It's not about what line voltage you use, it's about the energy capacity behind it, and the ability for high energy overvoltage transients to happen.

Any way of testing it? This will add spice to your videos, having cheap meters going in flames.
Drain the swamp.
 

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #77 on: February 07, 2015, 01:09:24 pm »
I agree with others that lying about CAT ratings and even voltage limits is inexcusable.

One thing that strikes me is the hodge podge of processors in this meter. If Lightages' schematics are accurate, the Cyrustek is the main meter, the MSP430FE425 is the wattmeter and the MSP430F149 does... LED and button management?!? These two MSPs are capable of much more, and I can't help but wonder that over the years and versions the original design simply became a collage of circuits and devices that increased the overall price of the BOM, which conversely required cost cutting measures on other areas such as the input protection.
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Offline Hootch

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #78 on: February 07, 2015, 01:15:42 pm »
It seems that there are different versions of this multimeter available. My UT71E has two HRC-fuses.
 

Offline max_torque

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #79 on: February 07, 2015, 01:16:14 pm »
It wouldn't be half as bad if they were just honest about the safety ratings- most people just don't need CatIV, but manufacturers seem obsessed with a "me-too" game of dishonestly copying competitors' specs and markings.

This x10 ^^^^


The issue for me is the blatant lying on the safety ratings on the meter case.  Now, i'm sure that You, or I, with lots of electronics experience would rightly, and with prior knowledge, take one look at such a meter and go "NO WAY" to using it on anything high voltage, but for every one of us, there are 100million other people who are not lucky enough to know or have learnt any better.
  For them, this IS a significant safety issue.  For example, anyone could say buy one of these meters secondhand anywhere, get it home, and go "hmm, i wonder if i can measure the mains voltage in my house" and take a look at the front, see the words "600V" and think, hey, excellent, this meter is perfect for that.

This is why CAT ratings were introduced, to help none expert users choose test equipment that is properly rated for the task.


So, once this basic issue is found, i couldn't care less if the inside of the meter is machined from solid gold, and uses unicorn horn hybrid un-obtainium trimmers or what ever!

 So, Uni-T, fix the basics, and THEN we can discuss if the meter is "value for money" or not.
 

Offline ptp170

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #80 on: February 07, 2015, 01:23:07 pm »
Absolutely. There is a reporting system in Europe to counter the practice. Flawed products have to be removed from the market. Not sure about fines.

Bet Maplin wouldn't agree to open up a meter and see what's inside!

Maplins remove and edit reviews people make on their website so not a chance in hell they're going to be honest about self reviewing multimeters!

One chap got really annoyed about a jump start battery pack so did a YouTube video on it.. quite funny as he includes the ridiculous quotes that Maplins used when 'justifying' themselves..
 

Offline Wytnucls

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #81 on: February 07, 2015, 01:23:55 pm »
It seems that there are different versions of this multimeter available. My UT71E has two HRC-fuses.
Yep. You have the more expensive 1KV European version. No independent testing though, so who knows if it meets the regulations.
And your MELF resistors are straight!  ;D
« Last Edit: February 07, 2015, 01:44:37 pm by Wytnucls »
 

Offline Wytnucls

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #82 on: February 07, 2015, 01:25:43 pm »
The RAPEX system doesn't work all that well. Only a handful of meters have been withdrawn so far:

http://ec.europa.eu/consumers/safety/rapex/alerts/main/index.cfm?event=main.search

(Type multimeter in the search area and tick all the relevant years)
« Last Edit: February 07, 2015, 01:29:14 pm by Wytnucls »
 

Offline Wytnucls

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #83 on: February 07, 2015, 01:41:03 pm »
I agree with others that lying about CAT ratings and even voltage limits is inexcusable.

One thing that strikes me is the hodge podge of processors in this meter. If Lightages' schematics are accurate, the Cyrustek is the main meter, the MSP430FE425 is the wattmeter and the MSP430F149 does... LED and button management?!? These two MSPs are capable of much more, and I can't help but wonder that over the years and versions the original design simply became a collage of circuits and devices that increased the overall price of the BOM, which conversely required cost cutting measures on other areas such as the input protection.
Actually, the basic design hasn't changed much at all. Bean counters probably had their say when it came to final component selection.
 

Offline Maxlor

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #84 on: February 07, 2015, 01:43:03 pm »
As for independent testing, here's the relevant page: http://etlwhidirectory.etlsemko.com/WebClients/ITS/DLP/products.nsf/4c8700f3b75987a08525777700583333/bb3d3302a13f93f086257ddd000985fc?OpenDocument

Of course, the 71 series is not there :)

Curiously, I see the 61 series on there, when just on account of the british fuses in Dave's (and mine) it'd fail the testing. It must be the newer improved version.

As for C.E.M., yup, they have some meters listed too: http://etlwhidirectory.etlsemko.com/WebClients/ITS/DLP/products.nsf/4c8700f3b75987a08525777700583333/10c795564af71fa185257b58000c8b3a?OpenDocument
These are some of their simpler models, none of their more expensive models are listed. Basically, it's just the 9-digit meters here: http://www.cem-instruments.com/en/pro/nsort15-2.html
 

Offline timb

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #85 on: February 07, 2015, 01:46:02 pm »
LOL "RAPEX"


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Offline mikro

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #86 on: February 07, 2015, 01:57:55 pm »
That is some poor manufacturing. Is there a solder bridge on that trimmer, which soldering side is shown at  12:33?
 

Offline Wytnucls

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #87 on: February 07, 2015, 02:05:56 pm »
It's not about what line voltage you use, it's about the energy capacity behind it, and the ability for high energy overvoltage transients to happen.

Any way of testing it? This will add spice to your videos, having cheap meters going in flames.
Testing the amp side is fairly easy, if you have access to a beefy 2000V supply.
Test with blown fuses in place for one minute to check for arcing.
Other ranges are more difficult to test, requiring high voltage and timed pulsed delivery. The meter doesn't need to function properly afterwards. The enclosure should be able to contain the damage though and no harm done to the user. Testing with constant high voltage and low source resistance doesn't prove anything and would defeat most multimeters.
Creepage and clearance should also be measured for compliance.
« Last Edit: February 07, 2015, 02:55:29 pm by Wytnucls »
 

Offline Tepe

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #88 on: February 07, 2015, 02:08:35 pm »
ceterum censeo systemd-inem esse delendam
 

Offline Tepe

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #89 on: February 07, 2015, 02:10:52 pm »
Mains adapter is suited only for EU
Schuko has nothing to do with the EU.
ceterum censeo systemd-inem esse delendam
 

Offline Tepe

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #90 on: February 07, 2015, 02:15:14 pm »
Mains adapter is suited only for EU
Schuko has nothing to do with the EU. It will fit neither this, at least not with a functional PE connection

nor this (same issue)

and definitely not this
« Last Edit: February 07, 2015, 02:18:54 pm by Tepe »
ceterum censeo systemd-inem esse delendam
 

Offline PChi

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #91 on: February 07, 2015, 02:18:35 pm »
I agree with Dave. I wasted a couple of hours probing a relatively high impedance circuit (a few hundred kohms) with a Tenma Multimeter only to find that the readings were being corrupted by mains hum. This was on a battery powered circuit so it was just random pick up by the meter. Ones based on the old 7106 / 7107 parts could be very good at rejecting hum but not the Tenma. If you are aware of the limitations the price isn't bad but you aren't buying a quality meter. All the miniature  presets don't inspire confidence in the long term stability. With test equipment the unwritten specifications are also important.
 

Offline ctz

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #92 on: February 07, 2015, 02:28:49 pm »
Here's the innards of a Tenma 72-7730A (€93), which is Farnell's whitelabelling of a UT71B (€105).
 

Offline Wytnucls

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #93 on: February 07, 2015, 02:29:36 pm »
Electromagnetic interference is quoted for 1V/m and below: Specified accuracy+5% of range. I seem to remember the Fluke 87 V was having an issue with interference too.
 

Offline mij59

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #94 on: February 07, 2015, 02:29:51 pm »
It seems that there are different versions of this multimeter available. My UT71E has two HRC-fuses.

Bought my UT71C from Reichelt, same fuses as yours, it came with some kind of compliance note, don't remember what it was about.
 

Offline Lightages

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #95 on: February 07, 2015, 03:59:09 pm »
BTW the safety issues with this meter has been known and published here for years.
https://www.eevblog.com/forum/testgear/a-list-of-multimeters-that-do-not-appear-to-meet-their-claimed-safety-specs/
and a quick search for UT71E would have brought up almost all the issues with it too. I was actually very surprised to see one in Dave's hands for a review after its history here.
 

Offline JoeLaBidouille

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #96 on: February 07, 2015, 04:07:59 pm »
In Europe, the UNI-T models are also sold under Conrad brand.
The Conrad VC920 is based on the same platform of the UT71 series.
Same PCB, same form factor... only a small difference for the color.

I took two pictures of this multimeter (red PCB)
In mine, the AD636 is a TO100 package.
At the bottom, two “thru the hole” resistors are used.

Always in UNI-T, I took a weird soldering picture of a UT61 (Conrad VC830) with a green PCB.

 

Offline parbro

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #97 on: February 07, 2015, 04:13:50 pm »
BTW the safety issues with this meter has been known and published here for years.
https://www.eevblog.com/forum/testgear/a-list-of-multimeters-that-do-not-appear-to-meet-their-claimed-safety-specs/
and a quick search for UT71E would have brought up almost all the issues with it too. I was actually very surprised to see one in Dave's hands for a review after its history here.
And yet the meters still remain for sale. What does that tell you about the ethics of UNI-T and their general regard for the customer?
 

Offline Nerull

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #98 on: February 07, 2015, 04:14:35 pm »
this way clearly a rant , can't say this is an objective review , we all know it's cheap product that do the job for low end application, as poor engineering, i think who ever built this is capable of designing a good one and uni-t is capable of manufacturing a high level multimeter BUT if everyone do that , no one will be able to buy a 15$ meter working for 4 years now.
so yeah they suck but ...they suck for a purpose.

 i think the spring is connected to the case shielding (not those for the buzzer) , so nothing wrong if it touch the shielding metal mounted in pcb.

Why is everyone throwing around the "Cheap $15 meter" excuse for a $180 meter? You can buy cheaper meters which do actually stand a chance in hell of meeting their ratings. Price isn't an excuse in this price range.
 

Offline jaxbird

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #99 on: February 07, 2015, 04:23:56 pm »
I guess Dave is happy that he is not in the US, otherwise the FTC would be all over his ass with the lack of clear disclosure etc. especially with their tightened rules for internet/youtube reviews.

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Offline TMM

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #100 on: February 07, 2015, 04:28:46 pm »
Why is everyone throwing around the "Cheap $15 meter" excuse for a $180 meter? You can buy cheaper meters which do actually stand a chance in hell of meeting their ratings. Price isn't an excuse in this price range.
Ethics of improper CAT ratings aside, you aren't going to find a meter which has the same features for any where near the same price. If you can overlook the pitfalls suddenly $180 doesn't look so bad when you consider that a 40000+ count datalogging meter like the Fluke 289 will set you back $540 and a power multimeter like the Gossen Metrahit Energy will hit you (no pun intended) for an eye watering $1200.

The current going price for a UT71E from a chinese seller on ebay is US$169.90 including international shipping and there is a Australian seller who has them for US$147.22 including national postage.
« Last Edit: February 07, 2015, 04:32:26 pm by TMM »
 

Offline Wytnucls

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #101 on: February 07, 2015, 04:30:48 pm »
BTW the safety issues with this meter has been known and published here for years.
https://www.eevblog.com/forum/testgear/a-list-of-multimeters-that-do-not-appear-to-meet-their-claimed-safety-specs/
and a quick search for UT71E would have brought up almost all the issues with it too. I was actually very surprised to see one in Dave's hands for a review after its history here.
It is old news. There are better UNI-T meters now, but they don't do Watts anymore, which Dave was after. I don't know what is written on the box, but the manual clearly stipulate that test voltage must fall between 50V and 250V AC only.
The best and cheapest meter for that type of measurement including energy, would be a second-hand 310,000 count Gossen 29S, with 0.1uW resolution, which usually sells for less than 400 Euros in Germany.
 

Offline Hootch

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #102 on: February 07, 2015, 04:46:03 pm »
Bought my UT71C from Reichelt, same fuses as yours, it came with some kind of compliance note, don't remember what it was about.

Yes indeed, my dmm is also from Reichelt. As you mentioned, there was a note. After a little search, I found it finally:

"Manual amendment
In order to meet new CE Standards, the following amendments are made:

Alligator Clamp - Removed

Safety Measuring Cable - Removed"

Nothing about fuses...
 

Offline allikat

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #103 on: February 07, 2015, 04:51:19 pm »
Re the Uni-61E:
Quote
BS 1362 specifies sand-filled ceramic-bodied cylindrical fuses, 1" (25.4 mm) in length, with two metallic end caps of 1/4" (6.3 mm) diameter and roughly 1/5" long. The standard specifies breaking time versus current characteristics only for 3 A or 13 A fuses.

For 3 A fuses: 0.02–80 s at 9 A, < 0.1 s at 20 A and < 0.03 s at 30 A.
For 13 A fuses: 1–400 s at 30 A, 0.1–20 s at 50 A and 0.01–0.2 s at 100 A.
Source: https://en.wikipedia.org/wiki/AC_power_plugs_and_sockets_-_British_and_related_types

Even if those fuses meet spec, are they good enough protection for your meter?  I mean, they claim to be BS1362 fuses, but are the wrong colour!
Quote
BS 1362:1973, allows any fuse rating up to 13 A, with 3 A (coloured red) and 13 A (coloured brown) as the preferred (but not mandated) values when used in a plug. All other ratings are to be coloured black.
Source: Same wiki page as above.

I know how they do these meters for the price, the same way a lot of junk electronics companies do. By bloody lying and using parts off the back of whatever's passing at the time.

By the way, the CE marking usually means "China Export", and it's an intentionally similar to the CE European conformity marking.
« Last Edit: February 07, 2015, 05:01:49 pm by allikat »
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Online AF6LJ

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #104 on: February 07, 2015, 05:03:02 pm »
Having seen those Uni-T meters at hamfests I was really wondering how good they were, now I need some Eye Bleach. GAAACHH What a pile of damp Cat Crap.
I guess I will still be looking for a new decent meter, my Beckman (Labeled as such and not Wavetek) RMS-225 I was given by Beckman to evaluate 24 years ago will have to fill the bill for some time before I retire it.

It is amazing the crap they pass off as test equipment these days.

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Offline Monkeh

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #105 on: February 07, 2015, 05:04:35 pm »
Even if those fuses meet spec, are they good enough protection for your meter?  I mean, they claim to be BS1362 fuses, but are the wrong colour!
Quote
BS 1362:1973, allows any fuse rating up to 13 A, with 3 A (coloured red) and 13 A (coloured brown) as the preferred (but not mandated) values when used in a plug. All other ratings are to be coloured black.
Source: Same wiki page as above.

And the 1A and 10A fuses shown in the UT61E are.. black!

By the way, the CE marking usually means "China Export", and it's an intentionally similar to the CE European conformity marking.

No, it means nothing of the sort.
« Last Edit: February 07, 2015, 05:11:23 pm by Monkeh »
 

Offline Wytnucls

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #106 on: February 07, 2015, 05:05:11 pm »
The fact that the chip is 20k count but the meter claims to be 40k count is pretty damming. Fake parts too... So unnecessary, there are quality low cost parts from Chinese manufacturers that will do the job, no need for a fake label on them.

Dave, maybe you should look at getting some equipment for testing installation at the rated voltages that manufacturers claim. See if you can get the magic smoke out.

I was worried when you removed that jumper, could have cleared calibration data or something. Seems okay though.

No need for the "one hung low" either, but otherwise an interesting and enlightening tear down.
It pays to read previous posts. Post #12 will tell you that Dave was wrong, the count of the Cyrustek chip on the 71E is actually 40,000, not 20,000.
 

Offline Monkeh

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #107 on: February 07, 2015, 05:12:04 pm »
By the way, the CE marking usually means "China Export", and it's an intentionally similar to the CE European conformity marking.

That's an urban myth, similar to the one about the Japanese town of Usa.

You are correct about the fuses though.

The fuses are black. How is he correct?
 

Offline G7PSK

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #108 on: February 07, 2015, 05:18:18 pm »
All this talk about the uni T meters has got me looking at other meters as I was thinking of getting another meter, so does anyone know anything about the Megger AVO410. I was thinking of getting one.
http://www.tester.co.uk/megger-avo410-digita-multimeter-cativ-600v

Or am I doomed to getting a yellow peril (Fluke)
 

Offline Wytnucls

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #109 on: February 07, 2015, 05:23:51 pm »
Perhaps not relevant to the thread, but your Megger is an Appa 73 meter. You're doomed.
 

Offline Lightages

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #110 on: February 07, 2015, 05:27:24 pm »
Which also appears to be an Ideal meter.
 

Offline TMM

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #111 on: February 07, 2015, 05:39:00 pm »
The fact that the chip is 20k count but the meter claims to be 40k count is pretty damming.
Dave made an oopsy - he pulled up the datasheet for the ES51922 instead of the ES51966 which is actually what is in the meter. It's a 44000/440000 count meter chip http://www.cyrustek.com.tw/spec/ES51966.pdf
There is however a catch - on resistance and current (at least when set to amps) the resolution does seem to be lower than 40000 because i've noticed that it has a tendency to snap to certain increments. It is perhaps operating in 4000 or 4400 actual counts with some averaging going on.
« Last Edit: February 07, 2015, 05:42:11 pm by TMM »
 

Offline lapm

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #112 on: February 07, 2015, 05:39:31 pm »
Edit relating 20.000 count crap...

Also if they lie about cat ratings, what else do they lie about? Or what else hidden treasures that meter has hidden inside it...
Electronics, Linux, Programming, Science... im interested all of it...
 

Offline Monkeh

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #113 on: February 07, 2015, 05:39:58 pm »
Ok now im seriously curious how they get 40.000 counts out of 20.000 count chip set...

You should really read the last few posts.
 

Offline Grapsus

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #114 on: February 07, 2015, 05:40:57 pm »
I don't get it why so many people think that Dave was somehow unfair with this meter and Uni-T in general. What is all this justification stuff ? Are you trying to make yourself feel better about having wasted 180$ and bought a crappy and dangerous meter ? There is a lot of alternatives : 1W resolution mains power meters can be bought for 20$ in any PC shop and for 150$ you can have a used 20000 counts Fluke.

The PCB is a horrible mess, it has every possible 5$-meter cost reduction trick except for a few precision parts to meet the announced precision. Look at every photo posted here, there is silkscreen for a spark gap "SG1" but it is always missing. Aside from cost reduction it looks like the designers just don't give a shit about their product, a screw hole in a 10A track, seriously ?!

Yes, from a single teardown like this we can deduce that Uni-T is a company that reduces costs, plays tricks on its customers and puts them in danger by claiming unmet security standards. Therefore all their products should be considered as dangerous crap until proven otherwise. And if they don't like this negative bias they are welcome to make good quality stuff for several years as others have done to earn their reputation.
 

Offline TMM

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #115 on: February 07, 2015, 05:52:27 pm »
I don't get it why so many people think that Dave was somehow unfair with this meter and Uni-T in general. What is all this justification stuff ? Are you trying to make yourself feel better about having wasted 180$ and bought a crappy and dangerous meter ? There is a lot of alternatives : 1W resolution mains power meters can be bought for 20$ in any PC shop and for 150$ you can have a used 20000 counts Fluke.
The ~$170 E variant is a bit of a gimmick but the cheaper versions without the power measurement have some merit. You aren't going to find a 40000 count datalogging meter with USB for $130 from anyone else. Hell most of the other manufacturers charge you that just for the USB cable.

I don't know why people find this so hard to understand. It's like all the car manufacturers selling V8 sports cars for $50,000. Then some chinese company comes along and sells a V8 sports car that is just as powerful for $7000 but the catch is that it has no seatbelts and the fit and finish is a bit naff. Suddenly everyone is like "Oh my God! you can't sell a car without seatbelts!". But who cares, it's $7000. Install them yourself if you are so inclined.

If all you want is a 20000 count multimeter without any bells and whistles then yeah buy an old second hand 87...
« Last Edit: February 07, 2015, 06:02:05 pm by TMM »
 

Offline Wytnucls

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #116 on: February 07, 2015, 06:04:55 pm »
On the 71D, 10,000 data memory, accessible on the meter or the PC. 30,000 on my Gossen 30M, but I have to buy the Gossen cable and software to see any of it (350$). That's after you paid 900$ for the meter, 60$ for the bag and 140$ for the 5V wall wart, otherwise you have 16 hours of battery life. Oh, it's only CAT II 600V, with 100mA max. And it comes with a bodged cap on the DC to DC converter.
« Last Edit: February 07, 2015, 06:24:28 pm by Wytnucls »
 

Offline Lightages

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #117 on: February 07, 2015, 06:47:05 pm »
There is a real point of contention here when we look at the UT71E. It is clearly, obviously, intended to be used on high energy circuits as it has an attachment and function that are required to be connected to a high energy circuit in order to use them. The design and execution of the meter is clearly, obviously, not up to the task in a safe manner. On this point alone, the UT71E is a piece of junk that is not suited to its task and could cause someone serious injury.


The majority of Uni-T meters are cheaply built and have less than minimal input protection. Some of the latest multimeters have much improved input protection and I am comfortable recommending the UT139C at least.
 

Offline Grapsus

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #118 on: February 07, 2015, 06:49:56 pm »
I don't know why people find this so hard to understand. It's like all the car manufacturers selling V8 sports cars for $50,000. Then some chinese company comes along and sells a V8 sports car that is just as powerful for $7000 but the catch is that it has no seatbelts and the fit and finish is a bit naff. Suddenly everyone is like "Oh my God! you can't sell a car without seatbelts!". But who cares, it's $7000. Install them yourself if you are so inclined.

Well in civilized countries it is a crime to knowingly sell cars that don't meet the required safety standards.
 

Offline Yago

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #119 on: February 07, 2015, 06:50:46 pm »
I don't get it why so many people think that Dave was somehow unfair with this meter and Uni-T in general. What is all this justification stuff ? Are you trying to make yourself feel better about having wasted 180$ and bought a crappy and dangerous meter ? There is a lot of alternatives : 1W resolution mains power meters can be bought for 20$ in any PC shop and for 150$ you can have a used 20000 counts Fluke.
The ~$170 E variant is a bit of a gimmick but the cheaper versions without the power measurement have some merit. You aren't going to find a 40000 count datalogging meter with USB for $130 from anyone else. Hell most of the other manufacturers charge you that just for the USB cable.

I don't know why people find this so hard to understand. It's like all the car manufacturers selling V8 sports cars for $50,000. Then some chinese company comes along and sells a V8 sports car that is just as powerful for $7000 but the catch is that it has no seatbelts and the fit and finish is a bit naff. Suddenly everyone is like "Oh my God! you can't sell a car without seatbelts!". But who cares, it's $7000. Install them yourself if you are so inclined.

If all you want is a 20000 count multimeter without any bells and whistles then yeah buy an old second hand 87...

How would you make that meter meet the CAT ratings?
A new PCB design and quality components?
How much would all that time, effort and parts cost in the end?
Be easier to buy a quality meter and paint Uni-t on the front, but then why would you.
 

Offline c4757p

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #120 on: February 07, 2015, 06:51:06 pm »
I don't know why people find this so hard to understand. It's like all the car manufacturers selling V8 sports cars for $50,000. Then some chinese company comes along and sells a V8 sports car that is just as powerful for $7000 but the catch is that it has no seatbelts and the fit and finish is a bit naff. Suddenly everyone is like "Oh my God! you can't sell a car without seatbelts!". But who cares, it's $7000. Install them yourself if you are so inclined.

I think you're saying this seriously, but many of us would consider such a statement to have a high likelihood of being satirical...
No longer active here - try the IRC channel if you just can't be without me :)
 

Offline TMM

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #121 on: February 07, 2015, 07:00:13 pm »
So we are all agreed that its a moral dilemma that the incorrect cat rating text is printed on the front panel of the meter and in the literature and that the meter doesn't actually represent horrible value for money? Good, I thought so too.


There is a real point of contention here when we look at the UT71E. It is clearly, obviously, intended to be used on high energy circuits as it has an attachment and function that are required to be connected to a high energy circuit in order to use them. The design and execution of the meter is clearly, obviously, not up to the task in a safe manner. On this point alone, the UT71E is a piece of junk that is not suited to its task and could cause someone serious injury
There is a disclaimer that the mains attachment is only to be used up to 250vac. Also to probe a household mains outlet only requires cat II. Whether or not the meter would pass cat II is a secondary matter but it certainly does not need to be catIV
« Last Edit: February 07, 2015, 07:10:41 pm by TMM »
 

Offline Yago

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #122 on: February 07, 2015, 07:09:32 pm »
It is criminal and life threatening, can't put a price on the latter.
So it represents the poorest of value for money.
 

Offline Quarlo Klobrigney

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #123 on: February 07, 2015, 07:13:33 pm »
I haven't read through all 9 pages yet because the teardown of the extremely DANGEROUS PIECE OF SHIT led me straight away to a case I read about where an electrician and a fire official were killed due to arc  flash.
They died because of Chinese shit manufacturing with safety as a no-thought. The meter the electrician used to check all 3 phases exploded and the result as I said...
Please read this trade journal regarding this story. NEVER use cheap meters across a circuit that can literally vapourize you in an instant. Make sure that it is of the proper CAT rating for the job and from a reputable manufacturer with real approvals. Sorry if this has been said and linked before, but I can't see someone getting hurt by equipment like this.
the link: http://ecmweb.com/arc-flash/case-deadly-arc-flash
« Last Edit: February 07, 2015, 07:16:13 pm by Quarlo Klobrigney »
Voltage, does not flow, nor does it go.
 

Online boffin

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #124 on: February 07, 2015, 07:21:46 pm »
I'm guessing Dave ended up with a Chinese knock-off of a Chinese cheap brand.  The PCB is likely just a copy, but the components/fuses are the cheapest knockoff they could find.

 

Offline TMM

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #125 on: February 07, 2015, 07:27:09 pm »
Cool story, I think we have got the point that you shouldn't probe a 3 phase power plant with one of these by now.

The point I'm trying to get across is that for someone who just plays with bench power supplies, USB and battery powered devices, the Uni-t meters represent good value for money. I for one am not going to lose sleep over owning a meter with the incorrect rating printed on the front panel if I don't need a rating in the first place.


The combination of the mains power dongle and a meter that claims cat ratings which it obviously does not meet is a bit of a faff. However, that does not mean you should paint all uni-t meters with the same brush and that is exactly what Dave and others have done.
« Last Edit: February 07, 2015, 07:30:42 pm by TMM »
 

Offline Quarlo Klobrigney

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #126 on: February 07, 2015, 07:35:05 pm »
Cool story, I think we have got the point that you shouldn't probe a 3 phase power plant with one of these by now.
The meter is mislabeled is my main point. One day in a pinch, or in a frenzied hurry, some unsuspecting fool will grab a meter and check the mains at home or at work, not realizing that given the right circumstances, the meter may kill them. Glass fuses with minimal spacing are not proper fuses for Arc-Flash protection. I certainly wouldn't leave the thing plugged in doing an unattended survey.
« Last Edit: February 07, 2015, 07:38:45 pm by Quarlo Klobrigney »
Voltage, does not flow, nor does it go.
 

Offline Grapsus

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #127 on: February 07, 2015, 07:40:05 pm »
I don't know why people find this so hard to understand. It's like all the car manufacturers selling V8 sports cars for $50,000. Then some chinese company comes along and sells a V8 sports car that is just as powerful for $7000 but the catch is that it has no seatbelts and the fit and finish is a bit naff. Suddenly everyone is like "Oh my God! you can't sell a car without seatbelts!". But who cares, it's $7000. Install them yourself if you are so inclined.

I think you're saying this seriously, but many of us would consider such a statement to have a high likelihood of being satirical...

I think there might be a cultural difference at play here. For example in western Europe or North America people trust regulations because those imply responsibility. Therefore in those countries you don't expect a large pothole on a highway because you know that somebody is responsible for maintaining the road in good condition. On the other hand, for example in Russia or India, I saw that people only count on themselves and assume that regulations are bullshit, so a one-meter pothole on the highway would not surprise them as much. Since Dave is from a country that is from the first kind, you can't expect him not to be shocked and say something like "wow ! a 40000 count data-logging meter for only 180 bucks, thank you Uni-T ! notice that it might blow your head off, but that's ok, we all know that CAT ratings are bullshit so just be careful when you probe a high energy circuit, after all, you're the only one responsible for your safety".
 

Offline TMM

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #128 on: February 07, 2015, 07:42:50 pm »
Cool story, I think we have got the point that you shouldn't probe a 3 phase power plant with one of these by now.
The meter is mislabeled is my main point. One day in a pinch, or in a frenzied hurry, some unsuspecting fool will grab a meter and check the mains at home or at work, not realizing that given the right circumstances, the meter may kill them.
Absolutely. I would like to see uni-t remove the cat markings from the offending meters because they are wrong. That said it is moronic to discount the entire line of uni-t meters for low energy usage (which, let's face it, is 99% of electronics use) just because they have false markings on them.


To the people who are dwindling on the fact that you can pay $180 for a meter and get very little in the way of safety - is it really that hard to believe that if you can buy a $180 fluke and get a lot of safety but very few features, you could also part with the same amount of cash for a multimeter that has a tonne of features and very little safety? Regardless of claimed ratings I think its fair to point out that its unreasonable to expect a tonne of features and fluke level safety/quality for the price point. If it was, then fluke would be out of business long ago.
« Last Edit: February 07, 2015, 08:02:57 pm by TMM »
 

Offline WackyGerman

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #129 on: February 07, 2015, 07:55:41 pm »
Well for 180 $ or here in europe for the same in euro :scared: it is really far away of a good value  :-- :--. For the same money you will get a second hand gossen or fluke with lightyears away better quality in construction , accuracy and input protection .  Even it has 40000 counts resolution this is not a tool . It is a dangerous toy where the packagaging and the carrying bag is more expensive in the production price than the meter itself .
Just keep your eyes open to get a good and cheap multimeter . It s easy to find this at ebay or sometimes on the fleamarket where my old shitty crappy looking norma D 3012 came from ( made in Austria , not in Australia ) . It is a 25000 counts multimeter and the accuracy almost meet the specifications except at 1 V it has 0.04 % instead of 0.02 % accuracy . But for me it is more than enough and anyway this puppy is roundabout 30 years old and it is not a trms meter . And at that time there were no cat ratings for multimeters . But for low energy measurements it is more than good enough and it will work many times longer than this cheap UNI-T s . I m going to make a teardown soon of this multimeter and put some pics here in the forum . By the way , I paid 15 Euro for this multimeter at the fleamarket  ;D
 

Offline Yago

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #130 on: February 07, 2015, 08:05:20 pm »
Cool story, I think we have got the point that you shouldn't probe a 3 phase power plant with one of these by now.


No you haven't got the point, and I am begging to think you are trolling here, and will report you for doing so soon.

It does not have "this is a dangerous piece of shit" written on the front does it?
If it did then there would be perhaps a case for this to be sold.
 

Offline Yago

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #131 on: February 07, 2015, 08:06:34 pm »
What does a Brymen cost in dollar equivalent?
 

Offline Rick Law

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #132 on: February 07, 2015, 08:08:44 pm »
...

I think there might be a cultural difference at play here. For example in western Europe or North America people trust regulations because those imply responsibility

....

Speak for your self, my friend.  There is nothing in our current administration (USA) that I trust. 
In fact, I assume for the most part the opposite is true.  The Constitution of The USA is written with the premise and the for reason that government cannot be trusted.

Case and point, the administration has been singing praises to themselves about the "low unemployment" and LinkedIn Pulse (their email alerts) latest "Pulse" is "The Big Lie: 5.6% Unemployment" written by Jim Clifton, CEO at Gallup.

Private labs such as UL carries far more weight to me than anything the USA government can say.

I fault UNI-T in carrying false labels.  This in my view is fraudulent.  I think UNI-T is good enough that it has a market without falsely claiming compliance.  It has a role even as a non CATx compliant meter.

I would like it better if UNI-T simply erase the label.  Since in some cases, the PCB already made provision, UNI-T can print on the box "Upgradable to CATx ???V compliant by authorized service agent".

Rick
« Last Edit: February 07, 2015, 08:16:20 pm by Rick Law »
 

Offline TMM

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #133 on: February 07, 2015, 08:12:36 pm »
It does not have "this is a dangerous piece of shit" written on the front does it?
If they replaced the cat text with that, would your perceived value of the product be better, worse or unchanged? I'm curious to know.

Numerous people have claimed that they consider it poor value for money solely based on the false cat rating so I'm curious if people would consider it better value if it made no claim to being safe at all

People don't seem to have an issue with sub $50 meters which make dubious claims about safety, so how is this one any different? Its more expensive but it also brings a tonne of features to the table.
« Last Edit: February 07, 2015, 08:23:31 pm by TMM »
 

Offline Yago

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #134 on: February 07, 2015, 08:20:34 pm »
A Brymen is much better value for money, and not that far off in price.

Do you have a UniT meter TMM ?
 

Offline TMM

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #135 on: February 07, 2015, 08:24:58 pm »
A Brymen is much better value for money, and not that far off in price.

Do you have a UniT meter TMM ?
I own a UT71D and a Fluke 87V...
 

Offline Yago

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #136 on: February 07, 2015, 08:28:46 pm »
A Brymen is much better value for money, and not that far off in price.

Do you have a UniT meter TMM ?
I own a UT71D and a Fluke 87V...

How do you feel about the quality of that Uni-t?
Have you opened it up?

A Brymen 857A is about $160 (from TME), plus some for delivery, but hey it is UL listed and built like a tank.
 

Offline TMM

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #137 on: February 07, 2015, 08:40:47 pm »
I thought the datalogging cable for the Brymen was expensive and it doesn't have internal datalogging memory? It probably works out to be close to double what I paid for the uni-t.

The quality of the uni-t is 'good enough' imo. Its not fluke-level but it doesn't feel like cheap junk either. The only thing that really sucks is the poor quality voltage/com jacks.
« Last Edit: February 07, 2015, 08:42:47 pm by TMM »
 

Offline Wytnucls

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #138 on: February 07, 2015, 08:45:24 pm »
The discussion about fuses is moot. If you're worried about glass fuses, buy the 1KV version. The real CAT rating is unknown; hopefully it is at least CAT II 600V, which would be sufficient for most of us. My Gossen has that rating and it doesn't even have a fuse on the mA range, just a polyswitch.
Independent testing is the only way to tell for sure what the CAT rating is. I wish IEC would stipulate that as a requirement, like they do for some other instruments. In the meantime, be safe and stay away from the meter if you have to test high energy circuits.
 

Offline Yago

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #139 on: February 07, 2015, 08:51:38 pm »
The discussion about fuses is moot. If you're worried about glass fuses, buy the 1KV version. The real CAT rating is unknown; hopefully it is at least CAT II 600V, which would be sufficient for most of us. My Gossen has that rating and it doesn't even have a fuse on the mA range, just a polyswitch.
Independent testing is the only way to tell for sure what the CAT rating is. I wish IEC would stipulate that as a requirement, like they do for some other instruments. In the meantime, be safe and stay away from the meter if you have to test high energy circuits.

Isn't it also about the meters ability to protect itself (MOVs etc)?
Lightages found that his Uni-t couldn't and died, he made a vid about it.
 

Offline Wytnucls

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #140 on: February 07, 2015, 08:58:39 pm »
MOVs are not a requirement, although it is probably wise to install.
The 71E didn't die, the 61E did. But it wasn't a CAT rating test at all. By the way, it doesn't matter if the meter dies, as long as the damage is contained.
 

Offline electr_peter

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #141 on: February 07, 2015, 08:58:57 pm »
On the 71D, 10,000 data memory, accessible on the meter or the PC. 30,000 on my Gossen 30M, but I have to buy the Gossen cable and software to see any of it (350$). That's after you paid 900$ for the meter, 60$ for the bag and 140$ for the 5V wall wart, otherwise you have 16 hours of battery life. Oh, it's only CAT II 600V, with 100mA max. And it comes with a bodged cap on the DC to DC converter.
Gossen 30M with 1 200 000 counts, stable reference and 4 wire measurement is not in the same league for price comparison. It is like comparing rotten apples and gold plated oranges.
Agilent/Keysight sell IR->USB interface for ~30$ USD. UNI-T IR->USB adapter is the same for all their meters I thinks - same adapter for 61, 70, 81 series at least. Gossen are on very expensive side for some reason with their adapters and SW.
 

Offline IshtarTor

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #142 on: February 07, 2015, 09:04:00 pm »
It does not have "this is a dangerous piece of shit" written on the front does it?
If they replaced the cat text with that, would your perceived value of the product be better, worse or unchanged? I'm curious to know.

Numerous people have claimed that they consider it poor value for money solely based on the false cat rating so I'm curious if people would consider it better value if it made no claim to being safe at all

People don't seem to have an issue with sub $50 meters which make dubious claims about safety, so how is this one any different? Its more expensive but it also brings a tonne of features to the table.

In any case, I would go for one of the newer models, which are both good value AND safe. And it's better if you buy it in Europe rather than in China, as chinese resellers may put crappy fuses instead of the correct ones. Or buy fuses as well.
« Last Edit: February 07, 2015, 09:16:18 pm by IshtarTor »
 

Offline Yago

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #143 on: February 07, 2015, 09:10:06 pm »
MOVs are not a requirement, although it is probably wise to install.
The 71E didn't die, the 61E did. But it wasn't a CAT rating test at all. By the way, it doesn't matter if the meter dies, as long as the damage is contained.

Yes, sorry about the model confusion, confusing to say the least (though UniT are not alone here!).
Not a question of user safety, more a question of the value, if the meter is electrically "fragile", not so much a bargain if it "joins the choir invisible" when something nasty happens.
Every time it needs replacing it effectively doubles in cost (if replaced with the same model).
Again, this is not a point about user safety, and not about high energy circuits, just unexpected high volts or perhaps wrong range selected (charged cap when in ohms mode sort of thing).
 

Offline Wytnucls

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #144 on: February 07, 2015, 09:14:13 pm »
All ranges are protected by crowbar circuits up to 1000V.
 

Offline Candid

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #145 on: February 07, 2015, 09:20:15 pm »
There seeme to be many different board designs. These are some pictures of my 71E that I bought some weeks ago. Only the MOVs have been added by me the rest is original. The board was already designed for adding MOVs so I only had to solder them in.

I just removed the metal can so you can see what there is under it in the 71E with maybe the newest board design. I got it from reichelt.de in germany.
« Last Edit: February 07, 2015, 09:23:24 pm by Candid »
 

Offline Candid

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #146 on: February 07, 2015, 09:21:29 pm »
And under the metal can.
 

Offline Candid

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #147 on: February 07, 2015, 09:22:30 pm »
Last Picture.
 

Offline Yago

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #148 on: February 07, 2015, 09:24:59 pm »
All ranges are protected by crowbar circuits up to 1000V.

Thanks again Wyt!

Lights vid is unclear as it is after the fact, wonder what the threshold for damage is?
Not specifically UniT, and as suggested before, be nice to see a range of meters incrementally hit with high voltages.
Find out at what point the damage occurs for each model, as it is part of the bang for buck (ooo bad punnage).
Again, not high energy, just high volts (high energy is another type of issue and vid altogether!).
 

Offline Wytnucls

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #149 on: February 07, 2015, 09:28:48 pm »
Interesting. So, there have been a few changes under the can. Part of the resistor network has gone surface mount (resistor network, voltage divider). The 4x2.5MOhms resistors in series are still through hole.
« Last Edit: February 07, 2015, 09:35:17 pm by Wytnucls »
 

Offline Lightages

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #150 on: February 07, 2015, 10:11:20 pm »
Modifying a multimeter with added MOVs or a spark gap does not make it safer, not necessarily. The design of the circuit board, the placement of the components, and the actual values are to be taken as a whole. It is possible that the current limiting resistors on the input jacks are not up to the task and putting an MOV in there is just adding a miniature bomb ready to go off if the current goes through it. I sincerely think that they aren't there as a cost cutting measure, but they could have been omitted to prevent a bigger problem that wasn't anticipated in the original design.

Labeling a meter with a specific safety rating incorrectly is wrong and no one can defend that. What is the harm? Well how about the person who is buying his first meter and watches some youtube video about meter ratings and sees that the UT71E is rated for CATIV 600V and then proceeds to use it on the meter connection to his house and gets seriously burned? This is not a problem? Sure the meter might be good value for the money, but only if you know that the ratings are a lie and know what you are buying.

No one can argue that meter with exactly the same specs is not a better meter if it has the correct CAT rating on it instead of a bogus one. No one can argue that a meter with a bogus rating is being sold truthfully. No one can argue that everyone has the time to take apart every meter on the market before they buy one and have them all tested individually for safety. That is what the standards are supposed to be for and why people die and get burned when they trust the CAT rating on a meter stuck on there by greedy assholes, culturally related or not. Thanks to off brand thieves and liars, people die. It is that simple.

That is why I started the thread about meters that don't appear to meet their CAT ratings, so that there was a reference and some guides for people to check. I have not updated it for a long time but it seems it needs to be again. How a sticky that is there for all to read with warnings about Uni-T meters has been missed, including by Dave, I don't know.

So Uni-T makes some shit meters, and some blatantly unsafe ones. DON"T BUY THEM. If they make safer ones, them buy them and send them a message that people don't want the bad ones. Unfortunately education and culture do play a part in this and where I live quality seems to be a joke and to ask for service is an insult. Mastech, Victor, Vichy, etc, all have deservedly bad reputations but then you get people here and other forums complaining about meter snobs who don't understand the needs of the less fortunate who don't have the money. Again what is the point of these discussions? EDUCATION. The poor and underprivileged need the same education so at least when the buy junk, they know, and they know the risks and limitations.

I have yet to see a Mastech I would recommend, nor a Vichy, most Digiteks no, and if I do recommend anything for anyone from the really budget class I make it a point to educate that the bogus CAT ratings are a joke and they should keep the probes out of the wall socket. Yes, not everyone has $100 to spend on a meter, some not even $50. This is exactly who needs to know what they are buying and why they need to be careful where they use it.

As far as the UT61E I had. It fried at 2500VDC. This was above the rated input but not above the impulse it is supposed to protect the user from. Maybe around 10mA passed through from the test and it caused nice sparks to jump around the selector dial. If it had been a 500A pulse the meter probably would have exploded. If you can see the spark at <10mA image the arc at 500A!!!

Again, say what you want about a meter having "value" even if it doesn't meet its safety rating. Go tell that to the people's friends and family who died in the story linked to earlier.

<Edited for grammar and spelling>
« Last Edit: February 07, 2015, 10:28:08 pm by Lightages »
 

Offline Quarlo Klobrigney

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #151 on: February 07, 2015, 10:30:51 pm »
You just about summed it up Lightages. Sounds about right to me.. :box: < It's a knockout!
« Last Edit: February 07, 2015, 10:41:03 pm by Quarlo Klobrigney »
Voltage, does not flow, nor does it go.
 

Offline Fungus

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #152 on: February 07, 2015, 10:35:11 pm »
Sure the meter might be good value for the money

But...that's the point. It isn't. $180 isn't a cheap meter by any standard. $180 for a meter where every single component is a cheap clone, several major design flaws, fake safety rating, marginal performance (the chip is a 20000 count device yet the meter claims 40000 count) isn't "good value". There are plenty of good meters at that price range, this one shouldn't be among them.

So Uni-T makes some shit meters, and some blatantly unsafe ones. DON"T BUY THEM. If they make safer ones, them buy them and send them a message that people don't want the bad ones.

Does it work like that? If people see other people using Uni-T meters they might assume it's a good brand. It isn't. The meter in this video was intentionally built to rip people off and make the maximum amount of profit. There's no other explanation IMHO.

« Last Edit: February 07, 2015, 10:38:21 pm by Fungus »
 

Offline Monkeh

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #153 on: February 07, 2015, 10:36:31 pm »
a meter where every single component is a cheap clone

Er, they are?

Quote
marginal performance (the chip is a 20000 count device yet the meter claims 40000 count)

No, the chip is a 44,000 count device.
 

Offline Fungus

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #154 on: February 07, 2015, 10:41:19 pm »
No, the chip is a 44,000 count device.

Watch the video again at time 17:15

 

Offline Monkeh

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #155 on: February 07, 2015, 10:42:55 pm »
No, the chip is a 44,000 count device.

Watch the video again at time 17:15

Watch the video again and look at the chip. Dave was wrong, it is an ES51966, which is a 44,000 count chip. It is clearly visible at 15:45.
 

Offline Fungus

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #156 on: February 07, 2015, 10:44:42 pm »
And let's not forget that Dave couldn't actually use the "Watts" function because they didn't supply the right plug for Australia.

(Probably just as well given the 1mm clearance between the input voltage line and GND. Would you connect it to something like a washing machine with a big motor?)

 

Offline Fungus

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #157 on: February 07, 2015, 10:45:31 pm »
Watch the video again and look at the chip. Dave was wrong, it is an ES51966, which is a 44,000 count chip. It is clearly visible at 15:45.

Ok, you win. I was just going by what the video said.
 

Offline Fungus

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #158 on: February 07, 2015, 10:54:23 pm »
a meter where every single component is a cheap clone

Er, they are?

Well, maybe not 100% of them. But far too many. When you're charging $180 the very least you could do is buy real part.

PS: I bet you're fun at parties...

 

Offline hamdi.tn

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #159 on: February 07, 2015, 11:07:07 pm »
some ppl gone too far with this killer meter , i used a Uni-t dirt cheap meter in main , in 3 phase main it work ok , and still alive  :phew:
i don't think that anyone here needed this video to actually be aware of how this meter quality is crap compared to any other high range brand, but again you know what you buying with your money, you know the risks related to it.
And i think some ppl here tend to forget that all of us started as hobbyist ... mean that you only have a limited amount of money to put it in one place, and a uni-t meter will surely be enough for the task and for the budget.
However lying about safety is certainly wrong and immoral, and they should correct that ...
 

Offline Fungus

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #160 on: February 07, 2015, 11:32:24 pm »
Value is all about matching price to expectations.

Would you not feel ripped off if you spent $180 on a meter then opened it up and saw what we saw in this video?




 

Offline sparx

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #161 on: February 07, 2015, 11:49:06 pm »
some ppl gone too far with this killer meter , i used a Uni-t dirt cheap meter in main , in 3 phase main it work ok , and still alive  :phew:
i don't think that anyone here needed this video to actually be aware of how this meter quality is crap compared to any other high range brand, but again you know what you buying with your money, you know the risks related to it.
And i think some ppl here tend to forget that all of us started as hobbyist ... mean that you only have a limited amount of money to put it in one place, and a uni-t meter will surely be enough for the task and for the budget.
However lying about safety is certainly wrong and immoral, and they should correct that ...

Just because you survived, doesn't mean that somebody else may connect it to 240v mains and it cause damage/injury/death.


Compare it to a vehicle, I get in my car and drive nearly every day. I'm sitting near enough on top of gallons of high power fuel with a relatively low flashpoint. I trust that the manufacturer has performed safety testing, and engineered in safety to the design. Same with the tyres and every other component.

When a manufacturer starts labelling equipment with markings/certifications which it does not have then they are undermiming those certifications/markings and what they mean, potentially resulting in future distrust in the markings as they will start to mean nothing! At least in that case I may be able to chase a global, massive, vehicle manufacturer for damages. I doubt you'd get a penny out of Uni-T.
 

Offline Nerull

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #162 on: February 08, 2015, 12:14:14 am »
Brymens are in the same price point, have almost all of the same features (except the near-useless watt range), and aren't built like shit.

No, a comparison between a Uni-T and a Gossen or brand-new Fluke isn't fair, but those aren't the only meters in the market. The Uni-T fails to compete with other meters in *its* price range.
 

Offline Leadfootin

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #163 on: February 08, 2015, 12:35:59 am »
If you want to know about our "safety rating" agencies, go to restorecsa.com which highlights some of the issues with CSA and it's ratings.

The articles will show you why not to trust any stated rating from one of these agencies.
 

Offline AlphZeta

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #164 on: February 08, 2015, 12:45:44 am »
For those who are not familiar with CAT rating requirements, from Wikipedia:

...The required values can vary from 0.04 mm for single insulation CAT II, 50 V, to 28 mm for double insulation CAT IV, 1000 V. The exact values are defined in the international standards.[1] Such standards should be followed rigorously during the design process of the appropriate equipment.

So yes, the fact it does not meet CAT IV standard is pretty clear.

But I wouldn't go so far as to discredit this meter altogether. Having the ability to measure power is one of its main selling point and most electricians only do mains related work and would not need an accuracy higher than 0.1 W.
 

Offline rageoftheblacksmith

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #165 on: February 08, 2015, 01:14:18 am »
Hello Dave and everybody else.
I'm writing here because i own a couple of UNI-T instruments but i am not a fanboy, neither am i trying to justify the money i spent on those things.

In the past i had to rely on a 830 and a 2905 chinese multimeters; i ain't posting pics because i suppose you all know what i am talking about.
In an emergency (woodworking workshop, very important machine stopped running) i had to search for the 400V 3-phase power with the 830; in another emergency i had to do the same (MIG welding machine) with the 2905. I was lucky, i'm still alive and both meters still pretend to work.

Back to recent times, my old no-brand LCR meter died and i wanted to replace it, so i went searching on ebay and i found this UNI-T LCR meter and i bought one.
When i got it in the mail i started testing it and i was pretty happy with it, the perceived quality was good so i decided to buy a multimeter from the same manufacturer and i got myself a 71D.

Unfortunately i wasn't on eevblog forum then and i found no information on UNI-T being bad; i can't afford a Fluke at the moment and i wonder if there is any intermediate segment between no-brand cheap shit, UNI-T down and The Real Instruments up. I thought i had a good deal with my UNI-T meters but now Dave says "don't buy that crap", more or less.

I've been thinking of buying an oscilloscope and, well, i would have gone for a UNI-T one but now i am not so sure.

Hope i wasn't boring you people, greetings and wishes,
rageoftheblacksmith.
 

Offline Lightages

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #166 on: February 08, 2015, 01:21:17 am »
There really needs to be a requirement here for people to state where they live before asking for any recommendations. This comes up over and over and over again. Where do you live? It is hard to tell you the best place to buy or what to buy if we have no idea where you are!
 

Offline rhdf

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #167 on: February 08, 2015, 01:32:43 am »
And that would likely be why Uni-T has no official distributors and meters are only available through third-party sellers on places like Amazon, Craigslist, eBay, etc.

If Uni-T had official ties outside China, that would expose them to lawsuits for wrongful death or injuries attributable to failure to meet their safety rating claims if there has been any.

Well, In Sweden they are sold by  At least 2 "big" chains. "Clas Ohlson", who sells some models as "UNI-T Clas Ohlson Edition" No idea whats special with that edition, but the package states "imported by Clas Ohlson".
The other one is "Kjell & Co" They seems to sell them "unbranded"
( non of them has the 71E model, only the 61D as "top model") But ~600 SEK is "OK" for hobbyists instead of the cheapest FLUKE for double the price
 

Online AG6QR

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #168 on: February 08, 2015, 01:36:16 am »
I've got an older Triplett meter (1101) which has engraved in the plastic case "NOT FOR USE ON HIGH ENERGY CIRCUITS".  It has a glass fuse inside, lacks proper input protection to pass CAT standards, but it meets my expectations.  It is what it is, and like Dave's first Micronta meter that he displayed in the Radio Shack video, it is capable of safely doing useful work within its limitations.

The UNI-T, on the other hand, clearly claims it meets CAT standards, but it doesn't.  The circuit board looks like it was even designed to hold proper fuses, but assembled without them.  The company obviously made a conscious decision to cut costs at the expense of safety, and they did it while maintaining the claim on the front of the meter that it meets CAT standards.  And they package the meter with the device to invite you to plug it into mains.

That's slimy and untrustworthy.  If I can't trust the company behind the meter, I won't really trust the readings from the meter.
 

Offline rolycat

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #169 on: February 08, 2015, 01:37:01 am »
There really needs to be a requirement here for people to state where they live before asking for any recommendations. This comes up over and over and over again. Where do you live? It is hard to tell you the best place to buy or what to buy if we have no idea where you are!
A poll a year ago showed a substantial majority in favour of requiring users to specify a country during registration. This can be a 'black flag' for those paranoid about revealing personal information on the net.

However, Dave does not appear keen.
 

Offline DanielS

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #170 on: February 08, 2015, 01:39:45 am »
Value is all about matching price to expectations.

Would you not feel ripped off if you spent $180 on a meter then opened it up and saw what we saw in this video?
Although it was not really a variable in my purchase decision for my UT61E, I certainly would not be happy that a device clearly labeled as Cat-IV like the 71E might only meet Cat-II and only up to 250V. Intentionally misleading people into believing the device is much safer than it actually is certainly does not earn positive marks from me and should not earn any from anyone.

If you are going to design a piece of equipment that only meets 250V Cat-II safety, do the world a favor and mark it as 250V Cat-II before you kill someone.
 

Offline rageoftheblacksmith

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #171 on: February 08, 2015, 01:40:32 am »
Where do you live? It is hard to tell you the best place to buy or what to buy if we have no idea where you are!

Sorry, Lightages, i didn't think that my location was important. I live in Italy and most of the chinese stuff i buy online comes either from Hong Kong or from stocks in the UK.
I wouldn't buy anything from the U.S.A. because stuff coming from there always seems to be involved in customs trouble.
Should i ever decide to buy a Fluke there should be no problem because they are supposed to be made in Germany, right?
 

Offline Yago

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #172 on: February 08, 2015, 01:47:33 am »
I'll say it again eh?
Brymen meters if you are in EU.

There's a few places to get them, TME, and our own Lightages or Franky(Iloveelectronics)
 


Offline rageoftheblacksmith

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #174 on: February 08, 2015, 02:11:04 am »
Thank you Yago and Lightages for the information.
 

Offline iampoor

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #175 on: February 08, 2015, 02:52:03 am »
The problem with buying these meters that lie about the safety ratings is that it encourages the manufacture to keep on making them!
 

Offline zapta

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #176 on: February 08, 2015, 03:11:25 am »
There really needs to be a requirement here for people to state where they live before asking for any recommendations. This comes up over and over and over again. Where do you live? It is hard to tell you the best place to buy or what to buy if we have no idea where you are!

I just adding that they live in my town and give advise accordingly.
Drain the swamp.
 

Offline TMM

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #177 on: February 08, 2015, 05:13:10 am »
If they replaced the cat text with that, would your perceived value of the product be better, worse or unchanged? I'm curious to know.

Numerous people have claimed that they consider it poor value for money solely based on the false cat rating so I'm curious if people would consider it better value if it made no claim to being safe at all

People don't seem to have an issue with sub $50 meters which make dubious claims about safety, so how is this one any different? Its more expensive but it also brings a tonne of features to the table.

If you are buying a meter with an expectation that it meets the claimed safety rating then yes it would be poorer value for money if it failed to meet them. Value is all about matching price to expectations. It isn't a measure of features per dollar.
Hmm. What i am having trouble understanding is how people are willing to accept that the chinese UT61 series for $60 is a good deal but the UT71 series for $130 isn't. Both promise cat IV and fail to deliver. The extra features justify the price hike over a UT61. I must have missed the memo that after a multimeter exceeds a certain $ point it MUST be safe, regardless of how useful it's features are otherwise, or it must be crucified on EEVBlog forums.

I'll admit the 71E seems to represent worse value compared to it's cheaper A/B/C/D brothers. A mains power dongle is obviously of limited usefulness when the input protection is of a low standard. That said, it's not reason alone to lump all of one brand of meters together and declare universally "Uni-T Meters Suck".
« Last Edit: February 08, 2015, 05:26:13 am by TMM »
 

Offline IshtarTor

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #178 on: February 08, 2015, 05:48:08 am »
For those who are not familiar with CAT rating requirements, from Wikipedia:

...The required values can vary from 0.04 mm for single insulation CAT II, 50 V, to 28 mm for double insulation CAT IV, 1000 V. The exact values are defined in the international standards.[1] Such standards should be followed rigorously during the design process of the appropriate equipment.

So yes, the fact it does not meet CAT IV standard is pretty clear.

But I wouldn't go so far as to discredit this meter altogether. Having the ability to measure power is one of its main selling point and most electricians only do mains related work and would not need an accuracy higher than 0.1 W.
Except that you DON'T want to use this on mains.
 

Offline Pentium100

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #179 on: February 08, 2015, 06:41:24 am »
Except that you DON'T want to use this on mains.
Why not? I don't think that the meter needs a lot of cats to be able to function when connected to the mains. And if you are worried about the meter blowing up somehow (wouldn't the probe melt first if you shorted the mains) just place it further away from you.
 

Online AG6QR

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #180 on: February 08, 2015, 07:00:13 am »
For those who are not familiar with CAT rating requirements, from Wikipedia:

...The required values can vary from 0.04 mm for single insulation CAT II, 50 V, to 28 mm for double insulation CAT IV, 1000 V. The exact values are defined in the international standards.[1] Such standards should be followed rigorously during the design process of the appropriate equipment.

So yes, the fact it does not meet CAT IV standard is pretty clear.

But I wouldn't go so far as to discredit this meter altogether. Having the ability to measure power is one of its main selling point and most electricians only do mains related work and would not need an accuracy higher than 0.1 W.
Except that you DON'T want to use this on mains.

I agree that it's a piece of crap that shouldn't be used.  But let me play devil's advocate for just a moment...

We all plug in various devices into mains -- lamps, power supplies, radios, computers, kitchen appliances, etc.  The only things which I commonly use that have proper HRC fuses are multimeters.  I've seen some junk inside of consumer goods that make that awful UNI-T look fantastically safe in comparison.  Yet most consumers survive their appliances.  Most general consumer goods that most of us plug in to mains are generally safe, yet they don't have CAT ratings, and they're not as rigorously designed as a top quality industrial multimeter.  What's the difference?

One difference is that meters are often being held in your hand as you stick them in the socket, so any explosion is right next to you.  Another is that meters may sometimes be used for probing around in the main power distribution panel, where very large currents are available.  But a big difference is that it's up to us, the users, to connect the meters to mains properly every single time.   And most meters have both a high impedance mode, for voltage measurement, and a low impedance mode, for current measurement.  The mistake that is too easy to make, and potentially deadly when made with a poor quality meter, is to probe a high energy voltage source when your probes are plugged into the current terminals.  There aren't many other devices which we regularly connect to mains that have this potential for deadly user error.

That mains dongle that comes with the UNI-T meter would seem to prevent the human error of mixing up the voltage and current probing.  That's worth something, in my book.

That dongle would seem to turn the Uni-T meter into a specialized mains power consumption meter that is almost as idiot proof as the P3 Kill-a-Watt meter (common in the USA).  The Kill-a-Watt does not claim a CAT rating. 

But even with the dongle, the UNI-T doesn't stack up well against the dedicated power meter.   The UNI-T costs nine times as much, has a worse resolution of 1 watt versus 0.1 watt for the P3 Kill-a-Watt meter, and the Uni-T doesn't measure cumulative energy over time, while the Kill-a-Watt does.  The Kill-a-Watt is a $20.00 specialized device for measuring power and energy consumption of mains-powered devices, not a general purpose multimeter.  Still, if you want a power meter for mains power, you could do worse than buying a Kill-a-Watt for that particular task, while buying a general purpose multimeter that doesn't make a false CAT claim for your other tasks.
 

Offline Fungus

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #181 on: February 08, 2015, 07:06:28 am »
it's not reason alone to lump all of one brand of meters together and declare universally "Uni-T Meters Suck".

Why not? This obviously intentional - somebody in management signed off on this meter and presumably gave the order to swap the expensive HRC fuses for cheap glass ones (to increase profit!)

Why would you buy anything from a company which does that?

Its only selling feature is the "Watts" function but that only works for large Wattages so it's useless (almost).

But I wouldn't go so far as to discredit this meter altogether. Having the ability to measure power is one of its main selling point and most electricians only do mains related work and would not need an accuracy higher than 0.1 W.

Why would an 'electrician' buy that multimeter when these things cost about $30?



You shouldn't be using a multimeter for finding live mains wires, use one of these instead (much faster/safer/easier!):



You can buy both of those, get a proper multimeter for electronics work (eg. the Brymen BM257) and still have change from $180. No need to keep Unit-T in business ripping people off.

 

Offline TMM

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #182 on: February 08, 2015, 07:14:53 am »
Why would an 'electrician' buy that multimeter when these things cost about $30?

Do tell me more about it 40000 count datalogging functionality and Cat IV safety. Oh wait.
 

Offline Fungus

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #183 on: February 08, 2015, 07:18:52 am »
let me play devil's advocate for just a moment...

The mistake that is too easy to make, and potentially deadly when made with a poor quality meter, is to probe a high energy voltage source when your probes are plugged into the current terminals.  There aren't many other devices which we regularly connect to mains that have this potential for deadly user error.

This is precisely what CAT ratings are for. One of the things a CAT rating tells you is that you can connect the meter to power with any combination of leads or range-selector setting and it won't kill you. If it fails, it will fail safely (should blow a fuse at most - no internal fires allowed).

The Kill-a-Watt does not claim a CAT rating. 

The Kill-a-Watt doesn't allow you to move leads around or select a low-impedance path through it.

That mains dongle that comes with the UNI-T meter would seem to prevent the human error of mixing up the voltage and current probing.  That's worth something, in my book.

Except that Dave couldn't actually use it in the country where he bought the meter - more evidence that they simply don't care about customers and don't deserve anybody's business.
« Last Edit: February 08, 2015, 07:24:18 am by Fungus »
 

Offline WackyGerman

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #184 on: February 08, 2015, 07:19:54 am »
Well this electrician would be sucidal to use this " multimeter " for power measurements on mains . Anyway if you look at the specs the multimeter is suited for 5 A continously and more than 5 A for 10 seconds . That means you can use it from 0.1 until 1150 Watts at cos phi 1 . Measuring power for 10 sec maximum is absolutely useless . This " multimeter " is a really bad joke and for 165 Euro ist is an absolutely rip off . The input jacks are shit , the clearance inside is shit , the fuses are shit , the overvoltage protection is shit , the trace to the com jack is shit , well it is in specs , but that doens t catch the world on fire . It is a dangerous slapped together piece of shit labelled with the wrong cat rating , sold for an astronomical price . normally it has to be banned from the market and been destroyed by the authority . Even if there are several versions on the market with better input protection and fuses , the board contruction has not enough clearance to meet the cat IV regulation . You can put in 100000 movs and ptc s and anything else but this " multimeter " never never never will meet the cat IV rating , no way !!!!!!
It is a good example of crap design and planned obsolescence . One small transient and the " multimeter " is dead and if you send it back they will tell you that you used it out of the voltage rating and don t send you a new one for free and that s it . Even if you don t use it on mains , the jacks never never would give good contact after more than 1000 connections with the probes and the contacts of the range switch will be worn out quickly , so this multimeter tightly may survive the guarantee  time and after that it is fit only for a knacker s yard
 

Offline TMM

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #185 on: February 08, 2015, 07:27:51 am »
The Kill-a-Watt doesn't allow you to move leads around or select a low-impedance path through it.
To be fair, neither does the UT71E when used in conjunction with the supplied mains dongle.

Except that Dave couldn't actually use it in the country where he bought the meter - more evidence that they simply don't care about customers and don't deserve anybody's business.
Pretty sure the meter Dave obtained is analogous to a grey import, regardless of what the 'distributor' would have him believe.
« Last Edit: February 08, 2015, 07:35:46 am by TMM »
 

Offline WackyGerman

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #186 on: February 08, 2015, 07:54:46 am »
Well by the way , electricians don t use the wall wart wattmeters because they are not accurate enough . In many of the VDE 701/702 insulation testers there is a built in function tester for the test item and this also measures power . But these testers are really special and cost a damn lot of money . For example the Fluke 2600-2 cost roundabout 1700 bucks .
 

Offline Fungus

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #187 on: February 08, 2015, 08:07:55 am »
Quote from: TMM
Except that Dave couldn't actually use it in the country where he bought the meter - more evidence that they simply don't care about customers and don't deserve anybody's business.
Pretty sure the meter Dave obtained is analogous to a grey import, regardless of what the 'distributor' would have him believe.

It will be interesting to see if Uni-T responds to this video, it could seriously affect their sales.

(I'm betting they won't, pretty much everything inside the meter is indefensible...)
« Last Edit: February 08, 2015, 08:10:42 am by Fungus »
 

Offline TMM

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #188 on: February 08, 2015, 08:29:01 am »
Quote from: TMM
Except that Dave couldn't actually use it in the country where he bought the meter - more evidence that they simply don't care about customers and don't deserve anybody's business.
Pretty sure the meter Dave obtained is analogous to a grey import, regardless of what the 'distributor' would have him believe.

It will be interesting to see if Uni-T responds to this video, it could seriously affect their sales.

(I'm betting they won't, pretty much everything inside the meter is indefensible...)
They have actually responded to the design of the UT71 before https://www.eevblog.com/forum/reviews/uni-t-multimeter-ut71d-unboxing-and-teardown/15/

I think Dave owes it to us to tear down a UT139, UT181 or UT171 series before making blanket statements about the entire brand.
« Last Edit: February 08, 2015, 08:34:25 am by TMM »
 

Offline classical

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #189 on: February 08, 2015, 08:43:09 am »
i can't afford a Fluke at the moment and i wonder if there is any intermediate segment between no-brand cheap shit, UNI-T down and The Real Instruments up. I thought i had a good deal with my UNI-T meters but now Dave says "don't buy that crap", more or less.
For my use as hobbyist I also bought a BM857A from TME. Delivery to Germany was very quick and without issues. Nice meter with very good value (at least when I bougt it). But regarding TME you have to add the VAT!
I also have access to a BM869 which in some aspects it is a better meter and the dual display can be very helpful e.g. measuring ripple or flickering of a lamp. So you alsways have correponding U=~ and U~ values in one sample. When I bougt the BM857 it was a bit cheaper than today and the difference to the BM257 was too low to think about it.
I also have access to a BM525 which is very fine for standalone data logging.
I've been thinking of buying an oscilloscope and, well, i would have gone for a UNI-T one but now i am not so sure.
watch Daves reviews on Rigol 1054Z
If this is too expensive look for a Rigol 1052e on sale or second hand.
 

Offline Tepe

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #190 on: February 08, 2015, 08:52:27 am »
What i am having trouble understanding is how people are willing to accept that the chinese UT61 series for $60 is a good deal but the UT71 series for $130 isn't. Both promise cat IV and fail to deliver.
Mt UT-61C bought from Reichelt in Germany is silk screened "CATIII 300V" and "CATII 600V". It also displays silk screened TÜVRheinland and GS logos. The TÜV logo for some reason says ID:0000000002, though.


« Last Edit: February 08, 2015, 09:00:18 am by Tepe »
ceterum censeo systemd-inem esse delendam
 

Offline iampoor

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #191 on: February 08, 2015, 08:53:17 am »
Quote from: TMM
Except that Dave couldn't actually use it in the country where he bought the meter - more evidence that they simply don't care about customers and don't deserve anybody's business.
Pretty sure the meter Dave obtained is analogous to a grey import, regardless of what the 'distributor' would have him believe.

It will be interesting to see if Uni-T responds to this video, it could seriously affect their sales.

(I'm betting they won't, pretty much everything inside the meter is indefensible...)
They have actually responded to the design of the UT71 before https://www.eevblog.com/forum/reviews/uni-t-multimeter-ut71d-unboxing-and-teardown/15/

I think Dave owes it to us to tear down a UT139, UT181 or UT171 series before making blanket statements about the entire brand.

Why dont you do the teardown? I think its a pretty safe bet to say that Dave wont be giving Uni-T any more Simoleans after this video.  >:D
 

Offline G7PSK

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #192 on: February 08, 2015, 09:13:30 am »
What is inside the power adapter for the meter, it could have its own shunts etc and not pass the full current and voltage to the meter, not that I will be buying one. I did however buy a UT61E on the recommendation's from this forum 2 years ago. I have now just joined the yellow peril brigade and ordered a Fluke 115 for work on power circuits this is to replace my old dinosaur AVO. I was thinking of an AVO410 but why buy a re-badge Chinese meter.
 

Offline WackyGerman

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #193 on: February 08, 2015, 09:16:05 am »
Well it is a little better than the 71E but still  :scared: :scared: :scared: . Look at the clearance between the 10A fuse and the shunt resistor . Must be 2 or 3 mm clearance . They still have to do their homework at UNI-T  :-- :-- :palm:
 

Offline G7PSK

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #194 on: February 08, 2015, 09:23:13 am »
Well it is a little better than the 71E but still  :scared: :scared: :scared: . Look at the clearance between the 10A fuse and the shunt resistor . Must be 2 or 3 mm clearance . They still have to do their homework at UNI-T  :-- :-- :palm:

Could be a safety feature, acts as a spark gap shunting a HV surge to ground before it goes through the meter.
 

Offline poorchava

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #195 on: February 08, 2015, 09:28:43 am »
I am using UT71A as one of my 2 main meters (the other one being a Fluke 87). In general I'm pretty satisfied with the accuracy I must say.  Other thing is that I don't do a great deal of mains connected stuff,  so the clearances and such are of little interest to me (and if I have to measure mains,  I use fluke anyway).

Brymen might be a better deal,  but the uni-t is not bad either,  if the safety ratings are not that big of a deal.
I love the smell of FR4 in the morning!
 

Offline WackyGerman

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #196 on: February 08, 2015, 09:36:40 am »
What is inside the power adapter for the meter, it could have its own shunts etc and not pass the full current and voltage to the meter, not that I will be buying one. I did however buy a UT61E on the recommendation's from this forum 2 years ago. I have now just joined the yellow peril brigade and ordered a Fluke 115 for work on power circuits this is to replace my old dinosaur AVO. I was thinking of an AVO410 but why buy a re-badge Chinese meter.

For sure there will absolutely nothing inside the adaptor except the parallel wiring to the V and Com and in serial to the A jack . If it would the price for the UT 71e would be 350 $ at that price policy of Uni-T . There needn t to be a shunt resistor or transformer in the adaptor , it is a superduper safe multimeter with cat IV rating  :-DD
 

Offline Fungus

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #197 on: February 08, 2015, 09:45:50 am »
Anyone notice the solder joint adjacent to the ADC pin 1 @ 8:55? It looks marginal at best.

Yes, I was wondering about that.

It looks to me like all the through-hole parts that come from underneath the board are hand-soldered. Look (for example) at the flux residue around the two joints to the left of the PTC at 5:50 (the ones labelled '+' and '-'). Definitely has a hand-soldered look to it.

 

Offline TMM

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #198 on: February 08, 2015, 09:46:37 am »
What i am having trouble understanding is how people are willing to accept that the chinese UT61 series for $60 is a good deal but the UT71 series for $130 isn't. Both promise cat IV and fail to deliver.
Mt UT-61C bought from Reichelt in Germany is silk screened "CATIII 300V" and "CATII 600V". It also displays silk screened TÜVRheinland and GS logos. The TÜV logo for some reason says ID:0000000002, though.



Yes, but most people who have purchased the UT61E have the chinese version with no MOVs/SGs and purchased it with the knowledge that it shouldn't be used on high energy circuits.
 

Offline Yago

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #199 on: February 08, 2015, 10:00:24 am »
What i am having trouble understanding is how people are willing to accept that the chinese UT61 series for $60 is a good deal but the UT71 series for $130 isn't. Both promise cat IV and fail to deliver.
Mt UT-61C bought from Reichelt in Germany is silk screened "CATIII 300V" and "CATII 600V". It also displays silk screened TÜVRheinland and GS logos. The TÜV logo for some reason says ID:0000000002, though.



Yes, but most people who have purchased the UT61E have the chinese version with no MOVs/SGs and purchased it with the knowledge that it shouldn't be used on high energy circuits.

Who are these "most people"?
Are you referring to the members of EEVBlog, because that is far from the numbers of these meters sold I'd GUESS.
Or do yo have number of meters sold and the education and experience of all buyers.

I already pointed out that the Brymen 857a(and you may get the improved 857S) is the same price from TME as the UniT is (I logged to get the gross price).
Why on earth would anyone even take the risk of any misleading posts about dangerous UniT here, when 857A is available.
Didn't someone here hack the Brymen data logging code too (I seem to remember a thread)?
 

Offline TMM

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #200 on: February 08, 2015, 10:09:15 am »
Who are these "most people"?
Are you referring to the members of EEVBlog, because that is far from the numbers of these meters sold I'd GUESS.
Or do yo have number of meters sold and the education and experience of all buyers.
The general impression that it get from reading posts on the internet, which has about as much merit as Dave's blanket statement that Uni-T has a bad reputation. Dave is actually violating Australian defamation law and would have a big problem if he made a similar statement about an Australian company.

I already pointed out that the Brymen 857a(and you may get the improved 857S) is the same price from TME as the UniT is (I logged to get the gross price).
Why on earth would anyone even take the risk of any misleading posts about dangerous UniT here, when 857A is available.
I've already pointed that out but just incase you have already forgotten - the Brymen meter with the datalogging cable costs over US$200 to my door. A UT71D which has a similar feature set, plus internal datalogging memory is around US$130. If safety was a concern i would absolutely not buy the Uni-T. If i only needed to use it for low energy circuits I would consider the tradeoffs of the Uni-T for a considerable price saving.
« Last Edit: February 08, 2015, 10:37:36 am by TMM »
 

Offline Yago

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #201 on: February 08, 2015, 10:21:57 am »
Yes, you did and I didn't forget.
I'll try and find that thread, at the moment got the mother of migraines.

I just put safety first, always.

Edit found this, might be worth a look:
https://gitorious.org/sigrok/libsigrok/commit/e493ec2aac301aae16b9aa42cb7574a857285c6f
« Last Edit: February 08, 2015, 10:31:14 am by Yago »
 

Offline G7PSK

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #202 on: February 08, 2015, 10:43:01 am »
Having just read through this thread and the Fluke data sheets Dave posted I have come to the conclusion that it is not just the CE marks you cannot trust but the CAT ratings as well even on a known brand like fluke as looking on the web I see what are more than likely fake Flukes.
Therefore the only safe route is to buy a meter made by an ISO 9001 registered company through another ISO 9001 registered company.
Before the ISO 9001 came along I used to do work for BNFL at Sellafield, I made low grade waste bins an sea water gate actuator levers as a sub contractor, I would buy Orlikon welding rods which were Lloyd's registered and still had to send a packet or two of each shipment to Lloyd's for testing as even back then in the early 80's there was fake products being sold and no documentation path.
So the only route to be taken to ensure absolute safety is but from an ISO registered stockist with all the associated extra costs.   
 

Offline 0b01010011

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #203 on: February 08, 2015, 10:44:50 am »
Inside the Tenma 72-7730A ordered about October 2014 from Farnell Australia.

The original 500mA HRC fuse was unbranded similar to how the 10A one is, but I blew that one during a moment of stupidity and had to replace it.
« Last Edit: February 08, 2015, 10:55:29 am by 0b01010011 »
 

Offline rob77

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #204 on: February 08, 2015, 10:52:48 am »
i'm glad i didn't buy the uni-turd meter :D i bought a Brymen 869S instead.... i(t was just 40Euro more expensive) took it apart just to see the input protection.. there is a significant difference... note the big-ass fuses, input resistors and several movs.

 

Offline Horstelin

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #205 on: February 08, 2015, 11:10:14 am »
I own a voltcraft VC940 (which is a labeled UNI-T 71E). I got it as a Christmas gift from my dad 2 years ago. He (like Dave) basicly bought it because of the Power measurement functions and since he doesn't know one's stuff in electrical engineering he had no idea even about what CAT ratings are.

My meter broke after I had used the power measurement function on a Wifi Printer which draws ~5-10 W. It's bricked, only shows +88.888 on the Display. I have found several persons on the internet who had the same problem (Mainly in German forums).

Of course, my dad did not keep the receipt so 180€ down the drain.

Guys stop defending UNI-T in respect to the 71E, it clearly isn't properly engineered enough to be connected to mains. Nevertheless they still sell it with an adaptor to connect it to the mains. And there are no shunt resistors whatsoever in that adaptor, everything is directly connected to the meter.

Still makes me mad that the store my dad bought it from seems to sell overpriced crap to people who have no idea what they are doing.

Cheers,  Urs
 

Offline EEVblog

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #206 on: February 08, 2015, 11:20:07 am »
Having just read through this thread and the Fluke data sheets Dave posted I have come to the conclusion that it is not just the CE marks you cannot trust but the CAT ratings as well even on a known brand like fluke as looking on the web I see what are more than likely fake Flukes.

To my knowledge there has never been a fake Fluke meter.
Some have come close, like "Fuke" and others that try to look similar, but have never seen a fake that looks exactly like a real fluke.
 

Offline EEVblog

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #207 on: February 08, 2015, 11:23:28 am »
It will be interesting to see if Uni-T responds to this video, it could seriously affect their sales.

It won't do diddly squat. People who want a cheap meter will always buy a cheap meter.
And may people simply don't care about proper input protection, and if you don't then, well, that's entirely your choice.
 

Offline EEVblog

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #208 on: February 08, 2015, 11:28:42 am »
I think Dave owes it to us to tear down a UT139, UT181 or UT171 series before making blanket statements about the entire brand.

If you read my video description I do say "generally suck".
Those "professional" ones (as they call them?) do look decent at first glance.
But if Uni-T do make a couple of decent meters, the fact remains that it seems that the majority of meters they make a built down to a price and cut so many corners.
I have no doubt Uni-T are capable of making a decent meter if they really want, but they just fail to do it so often people come to expect that from them.
They have very much earned the reputation they have ended up with.
« Last Edit: February 08, 2015, 11:30:23 am by EEVblog »
 

Offline FrontSideBus

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #209 on: February 08, 2015, 11:46:16 am »
I must admit, I was recently after a decent electronics multimeter. Previously I've been using an AC/DC clamp meter and while it was good for basics measurements, I wanted something more precise.
I was looking at some of the "high-end" Uni-T meters and thought about it for a while but after reading several very, very mixed reviews I saved a bit of money and got an ex Australian Defence Force Tektronix DMM916 sent over to the UK from a surplus dealer in AU, champion.
I'm glad I did that now after seeing this video!
« Last Edit: February 08, 2015, 11:48:09 am by FrontSideBus »
 

Offline firewalker

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #210 on: February 08, 2015, 11:50:55 am »
I believe the subject is over analyzed. The are using fake ratings. That's it. If they were stating the truth, no one could say anything.

Alexander.
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Offline R_Gtx

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #211 on: February 08, 2015, 11:55:30 am »
Why is everybody confusing the CAT rating, which on all meters applies only to the V-R-.. input ranges with overload protection, which is applicable to the I inputs. Yes, HRC fuses are preferable, but they are not in the high impedance input so do not impact on that inputs CAT rating.
« Last Edit: February 08, 2015, 12:00:24 pm by R_Gtx »
 

Offline G7PSK

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #212 on: February 08, 2015, 12:09:54 pm »
Having just read through this thread and the Fluke data sheets Dave posted I have come to the conclusion that it is not just the CE marks you cannot trust but the CAT ratings as well even on a known brand like fluke as looking on the web I see what are more than likely fake Flukes.

To my knowledge there has never been a fake Fluke meter.
Some have come close, like "Fuke" and others that try to look similar, but have never seen a fake that looks exactly like a real fluke.
I was looking today on E bay and saw quite a few 87's that were supposedly like new with protection film still on etc the probes did not look right and they were asking a third of the price as a buy now that other used were selling at auction for.
 

Offline Fungus

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #213 on: February 08, 2015, 12:18:38 pm »
Why is everybody confusing the CAT rating, which on all meters applies only to the V-R-.. input

Nope. The CAT rating says that you can connect the maximum rated input (eg. 600V AC) to any input with the range selector set to any position.

Yes, HRC fuses are preferable

Here's a case of an exploding multimeter that killed two people and badly injured another because of ... a glass fuse:

http://ecmweb.com/arc-flash/case-deadly-arc-flash

 

Offline eV1Te

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #214 on: February 08, 2015, 12:23:39 pm »
... I've already pointed that out but just incase you have already forgotten - the Brymen meter with the datalogging cable costs over US$200 to my door. A UT71D which has a similar feature set, plus internal datalogging memory is around US$130. If safety was a concern i would absolutely not buy the Uni-T. If i only needed to use it for low energy circuits I would consider the tradeoffs of the Uni-T for a considerable price saving.

A long time ago I did use a Uni-T meter to measure the incoming mains line to my building, after seeing this video I am happy nothing went wrong because I was unaware of these safety issues!

Maybe you know that your meter is only good for low voltage measurements, but you might lend it to a family member or a friend that then uses it for another purpose.

I would not have a problem with Uni-T if they labeled their multimeters as Cat-II 300V.
 

Offline timb

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EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #215 on: February 08, 2015, 12:46:27 pm »
For portable data logging, I bought three of those $25 Digitek meters. Comes with not-as-cheap feeling probes, RTD and the USB cable. It's even CAT II rated.

For lab use, I don't know why anyone would bother with this $180 piece of garbage when you can get something like a used 5.5 digit Keithley 197A benchtop meter for $100 on eBay and a GPIB to USB adapter for $50. (They're small, lightweight and even have provisions for a battery pack!)


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Offline Owen

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #216 on: February 08, 2015, 12:52:22 pm »
Nope. The CAT rating says that you can connect the maximum rated input (eg. 600V AC) to any input with the range selector set to any position.

And why is Brymen using 0.63A/500V and 10A/600V fuses in their BM257? Because they specified three different CAT ratings for their volt and amp ranges: mA -> CATIII 500 V(ac) 300 V(dc), A -> CATIII 600 V(ac) 300 V(dc), V -> as it's shown on the multimeter. I don't like that either. No I'm not a fanboy of Brymen and/or Uni-T, but that's why i bought an Agilent/Keysight U1272A and i love it.
 

Offline eV1Te

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #217 on: February 08, 2015, 12:53:55 pm »
I started reading a bit more in this thread, but not all the posts so maybe someone has brought this up before.

It seems that a few people does not know what happens when you accidentally short a high energy power line with a multimeter and then pull away the probes so that you get an arc that can span between the phases. The initial short might be due to a transient in the power line that arcs inside the DMM or the operator might have used the current setting instead of voltage with incorrect fuses in the DMM.


Here is a controlled experiment of what happens if you get this type of short from a faulty DMM (not a real person in the video)
« Last Edit: February 08, 2015, 12:57:46 pm by eV1Te »
 

Offline Yago

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #218 on: February 08, 2015, 01:37:21 pm »
Nope. The CAT rating says that you can connect the maximum rated input (eg. 600V AC) to any input with the range selector set to any position.

And why is Brymen using 0.63A/500V and 10A/600V fuses in their BM257? Because they specified three different CAT ratings for their volt and amp ranges: mA -> CATIII 500 V(ac) 300 V(dc), A -> CATIII 600 V(ac) 300 V(dc), V -> as it's shown on the multimeter. I don't like that either. No I'm not a fanboy of Brymen and/or Uni-T, but that's why i bought an Agilent/Keysight U1272A and i love it.

Could only guess that the meter is only capable of measuring up to 8 Amp, and displays an over range.

One thing that is sure, is that it will interrupt dangerous currents safely, as it has been tested so by the UL.
 

Offline Quarlo Klobrigney

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #219 on: February 08, 2015, 02:17:35 pm »
Which is why I posted the link on page 9 to the EC&M article about arc flash. I read this at the time in the print version of the magazine and took it to heart. See, I foolishly did the same thing where I worked when a 750KVA transformer blew one of its phases. I used a trusted meter, a Fluke and probed the 480V 3 phase 400A distro box with no cover on it now. It was all "hurry up find out we're losing money!"  Because all of the "engineers" in the plant had their thumbs up their ass, I decided to take action.They were having a debate by staring at the open box wondering how electricity flowed, so I was pro-active.
Yes nothing happened, but after reading that story I will never probe a high energy circuit with any multimeter, especially when it is in distress. It's not worth the gamble.
My point is again is that this meter is a blatant lie in regards to the CAT ratings on the face and inside as well. It is a disaster waiting to happen.
It seems that a few people does not know what happens when you accidentally short a high energy power line with a multimeter and then pull away the probes so that you get an arc that can span between the phases.
Here is a controlled experiment of what happens if you get this type of short from a faulty DMM (not a real person in the video)

« Last Edit: February 08, 2015, 02:25:51 pm by Quarlo Klobrigney »
Voltage, does not flow, nor does it go.
 

Offline G7PSK

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #220 on: February 08, 2015, 03:33:05 pm »
We need to send some meters to Photoinduction so that he can test them including a Fluke as I suspect that his HV supply will see a Fluke off as well but how soon and at what voltage would be interesting.
 

Offline DanielS

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #221 on: February 08, 2015, 04:10:42 pm »
Who are these "most people"?
Are you referring to the members of EEVBlog, because that is far from the numbers of these meters sold I'd GUESS.
Or do yo have number of meters sold and the education and experience of all buyers.
The general impression that it get from reading posts on the internet, which has about as much merit as Dave's blanket statement that Uni-T has a bad reputation. Dave is actually violating Australian defamation law and would have a big problem if he made a similar statement about an Australian company.
I do not see how Dave could be liable for defamation for pointing out how Uni-T disregarded safety with blatantly false Cat-III/IV ratings. That would be a violation of trade (misrepresentation, misleading advertising) and occupational safety laws in many countries. Uni-T rightfully deserves to get named and shamed for it.

It is not defamation when the "defamatory" comments are undeniable facts.
 

Offline Lightages

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #222 on: February 08, 2015, 04:27:35 pm »
In answer to Brymen has used lower rated fuses than the CAT voltage rating in their older meters, it was allowed by the regulations at the time. They still had designed the circuit board correctly and used full HRC fuses capable of breaking the appropriate pulse current specified in the CAT rating tests. The only difference was that the fuse was a lower rated voltage.

This is no longer allowed by the latest regulations so Brymen has revised all their meters that they produce to match the latest requirements. The BM257 is now known as the BM257s and has fuses matching the voltage rating of the rest of the meter. To be clear, the fuses have always been capable of the interruption current needed for the CAT rating on the meter. The difference between the old Brymens and the UT71E is night and day for safety.
 

Offline mariush

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #223 on: February 08, 2015, 04:32:29 pm »
Dave, you should update the blog post (or main website) and change the link and text for the correct cyrustek IC.  Maybe also put a note on the video to correct what you said - you say in video they're using 20k count dmm chip instead of 40k.

 

Offline Nerull

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #224 on: February 08, 2015, 04:33:40 pm »
Who are these "most people"?
Are you referring to the members of EEVBlog, because that is far from the numbers of these meters sold I'd GUESS.
Or do yo have number of meters sold and the education and experience of all buyers.
The general impression that it get from reading posts on the internet, which has about as much merit as Dave's blanket statement that Uni-T has a bad reputation. Dave is actually violating Australian defamation law and would have a big problem if he made a similar statement about an Australian company.

 :-DD :-DD :-DD
 

Offline c4757p

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #225 on: February 08, 2015, 04:42:56 pm »
As much as I thought that most of the opinions he gave in this video were silly (exception being the safety standards bit), anyone bleating about it being illegal to give such opinions really ought to just shut up and let this viewpoint die. They're opinions for fuck's sake. "Dave's blanket statement that Uni-T has a bad reputation" is an opinion, unless there's some objective notion of what makes up a "bad reputation".
No longer active here - try the IRC channel if you just can't be without me :)
 

Offline Pentium100

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #226 on: February 08, 2015, 05:31:10 pm »
I once shorted out the mains outlet with a really cheap meter (with unfused 10A range). The meter survived, part of the probe pin vaporized though.

And I do not have access to a 10kV line or even a 100A line. Maybe shorting out 400V 100A line could make the meter explode...

Also, most of the devices connected to the mains (except multimeters) have glass fuses rated for 250V. If that fuse is good enough for a radio, PC or an amp, why a multimeter containing the same fuse should not be connected to the mains?

 

Offline rob77

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #227 on: February 08, 2015, 05:39:36 pm »
I once shorted out the mains outlet with a really cheap meter (with unfused 10A range). The meter survived, part of the probe pin vaporized though.

And I do not have access to a 10kV line or even a 100A line. Maybe shorting out 400V 100A line could make the meter explode...

Also, most of the devices connected to the mains (except multimeters) have glass fuses rated for 250V. If that fuse is good enough for a radio, PC or an amp, why a multimeter containing the same fuse should not be connected to the mains?

you have a circuitbreaker/fuse (usually 6/10/16Amp here in Europe) in the line which is providing the power to that radio.... but in the distribution panel you have lines with 100+ Amp fuses..... that's why there are CAt II, III, IV ratings.. CAT II is good enough to poke around in the house - and a glass fuse is kind of OK for CAT II.  CAT IV must have "giant" HRC fuses to be able to disconnect the circuit safely when the meter is used in the distribution panel.
 

Offline classical

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #228 on: February 08, 2015, 05:42:36 pm »
Also, most of the devices connected to the mains (except multimeters) have glass fuses rated for 250V. If that fuse is good enough for a radio, PC or an amp, why a multimeter containing the same fuse should not be connected to the mains?
Please read http://en.wikipedia.org/wiki/Measurement_category for CAT definition.
A mains outlet is different from the mains inlet into your house. within your house you have additional breaker which are lower rated and help a lot.
 

Offline Lightages

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #229 on: February 08, 2015, 05:43:23 pm »
It is a good argument that glass fuses in any equipment connected to the mains is a bad idea. In fact, in England, all equipment connected to mains is supposed to have a specifically designed ceramic fuse.

But the main difference is with a multimeter is that you are intentionally connecting a direct short across two test points. This is much different than providing a backup protection for a piece of equipment that normally runs without shorts.

If you have a multimeter that is rated CATI/250V, then glass fuses are acceptable. If you have a meter rated for CATIII then they are not acceptable.
 

Offline classical

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #230 on: February 08, 2015, 05:44:17 pm »
Also, most of the devices connected to the mains (except multimeters) have glass fuses rated for 250V. If that fuse is good enough for a radio, PC or an amp, why a multimeter containing the same fuse should not be connected to the mains?
Please read http://en.wikipedia.org/wiki/Measurement_category for CAT definition.
A mains outlet is different from the mains inlet into your house. within your house you have additional breaker which are lower rated and help a lot.
 

Offline Jay_Diddy_B

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #231 on: February 08, 2015, 05:53:16 pm »
I once shorted out the mains outlet with a really cheap meter (with unfused 10A range). The meter survived, part of the probe pin vaporized though.

And I do not have access to a 10kV line or even a 100A line. Maybe shorting out 400V 100A line could make the meter explode...

Also, most of the devices connected to the mains (except multimeters) have glass fuses rated for 250V. If that fuse is good enough for a radio, PC or an amp, why a multimeter containing the same fuse should not be connected to the mains?



The issue is fault currents. Essentially the closer you are the source of the electrical power the higher fault currents. Fuse and breakers are given a interrupting capacity. The danger is that if the fuse cannot interrupt the current a plasma will form which is conductive and by-pass the fuse.

CAT 1 is for circuits that are not directly connected to the mains.

CAT II is for sub-circuits. The wall outlets in your house would normally be included in this category.

CAT III would be the distribution panel in your house. An outlet close the panel may be CAT III

CAT IV is for industrial applications, power entry into building etc.

Most of the catastrophic accidents occur when a multi-meter with inadequate safety is used.

The danger with a DMM is might be set on the wrong range, for example the current range and then connected to a supply with very high fault currents. This can trigger a plasma, like arc welding, and is called an arc-flash event.

A small fuse can protect some appliances because they are connected to circuits with lower fault current ratings.

Jay_Diddy_B
 

Offline Fungus

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #232 on: February 08, 2015, 06:05:46 pm »
I once shorted out the mains outlet with a really cheap meter (with unfused 10A range). The meter survived, part of the probe pin vaporized though.

The issue is fault currents. Essentially the closer you are the source of the electrical power the higher fault currents. Fuse and breakers are given a interrupting capacity. The danger is that if the fuse cannot interrupt the current a plasma will form which is conductive and by-pass the fuse.

This is why HRC fuses are filled with sand - to prevent that plasma from forming.

Glass fuses can also explode with enough force to bend the metal of the fuse holder out of shape and touch other parts of the meter internally (this is why flukes have blast walls all around the fuse area even though they use HRC fuses!)

Here's a cautionary tale of an exploding multimeter that killed two people and badly injured another. The suspected reason? It had glass fuses in it.

http://ecmweb.com/arc-flash/case-deadly-arc-flash

 

Offline Monkeh

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #233 on: February 08, 2015, 06:05:59 pm »
It is a good argument that glass fuses in any equipment connected to the mains is a bad idea. In fact, in England, all equipment connected to mains is supposed to have a specifically designed ceramic fuse.

Which is not internal to the equipment and has nothing to do with protection of the equipment. Nor is it present on any equipment connected via means other than a BS1363 plug or a fused connection unit designed to replace said plug. There is a substantial amount of this equipment in the home.
 

Offline rob77

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #234 on: February 08, 2015, 06:11:03 pm »
my 2cents for those who don't know....

HRC fuse has sand in it, and it's bigger.... that's the whole point - if the fault current (in kilo-Amps range) is blowing a fuse, the wire in the fuse is instantly vaporized - the sand will simply extinguish the arc by cooling the plasma (former wire) very quickly - combined with the longer distance for the arc it yields a very good disconnect capability.

small glass fuse - once the wire is vaporized - the air / gas in the fuse is not able to cool the plasma (former wire) quick enough and the plasma becomes a short - letting even more current to flow, heating up even further till the whole multimeter explodes, PCB traces are vaporised - providing even more plasma to conduct across the wires - this will go like avalanche - it will go like that till wires are melted and the distance between the wires will be large enough to extinguish the arc.

however with small fault currents the glass fuse is just ok - because it can't heat up so rapidly (less energy blows the fuse).
 

Offline Lightages

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #235 on: February 08, 2015, 06:12:23 pm »
It is a good argument that glass fuses in any equipment connected to the mains is a bad idea. In fact, in England, all equipment connected to mains is supposed to have a specifically designed ceramic fuse.

Which is not internal to the equipment and has nothing to do with protection of the equipment. Nor is it present on any equipment connected via means other than a BS1363 plug or a fused connection unit designed to replace said plug. There is a substantial amount of this equipment in the home.

I stand corrected. I thought that all equipment was required to have the BS1363 fuse.
 

Offline DanielS

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #236 on: February 08, 2015, 06:13:45 pm »
I once shorted out the mains outlet with a really cheap meter (with unfused 10A range). The meter survived, part of the probe pin vaporized though.

And I do not have access to a 10kV line or even a 100A line. Maybe shorting out 400V 100A line could make the meter explode...
If you want/need to poke around inside a breaker box, the fuse/breaker bus-bars can carry 100-200A depending on what the entrance breaker/fuses are, more if you account for surge ratings. If you probe the mains entrance terminals, then you have a completely unprotected connection directly to the local low-voltage distribution transformer which can provide a short-circuit current well over 1kA, enough to make your probe leads explode if nothing else blows first.
 

Offline Monkeh

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #237 on: February 08, 2015, 06:16:58 pm »
It is a good argument that glass fuses in any equipment connected to the mains is a bad idea. In fact, in England, all equipment connected to mains is supposed to have a specifically designed ceramic fuse.

Which is not internal to the equipment and has nothing to do with protection of the equipment. Nor is it present on any equipment connected via means other than a BS1363 plug or a fused connection unit designed to replace said plug. There is a substantial amount of this equipment in the home.

I stand corrected. I thought that all equipment was required to have the BS1363 fuse.

Absolutely not. Not only does it have nothing at all to do with the equipment (it protects the cable) the fuse (A BS1362 fuse..) is only required to protect said cables from the excessive continuous current available on a 30/32A ring final circuit. This means: Every switch, every light fitting, every smoke alarm, any equipment over 13A (and most over 10A), and anything not fitted for a BS1363 plug (substantial amounts of industrial and commercial equipment, most hardwired equipment) has no contact with a BS1362 fuse.
 

Offline Pentium100

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #238 on: February 08, 2015, 06:41:13 pm »
If you want/need to poke around inside a breaker box, the fuse/breaker bus-bars can carry 100-200A depending on what the entrance breaker/fuses are, more if you account for surge ratings. If you probe the mains entrance terminals, then you have a completely unprotected connection directly to the local low-voltage distribution transformer which can provide a short-circuit current well over 1kA, enough to make your probe leads explode if nothing else blows first.

In which case the multimeter is good enough. The power to my house comes from an outside panel with the meter and a 3x16A breaker. I do not have access to that panel, it belongs solely to the power company. The breaker panel inside my house is thus current limited by the breaker. So, unless I break the law and either open the panel with the meter or break into a substation, I probably would not be able to make the meter explode by accident.
 

Offline Yago

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #239 on: February 08, 2015, 06:54:25 pm »
Huh, I posted a question in here a few minutes ago... oops.

I was asking about the length of cable run from the high energy source providing an inductance that resists the initial current surge.
So the closer you are to the high energy source the higher the danger.
This also being part of CAT ratings and fuse requirements.
 

Offline yaputya

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #240 on: February 08, 2015, 07:04:37 pm »
The weird ass adapter looks like it has the classic European mains sockets (well, most of Europe)

It's the standard Euro plug alright - called a pig's nose for obvious reasons. The socket is recessed about 2cm with the two holes at the bottom and two springs on the sides for earth, they look pretty strange compared to the flat Aussie type. Also they are not polarised, so Active and Neutral can be on either pin. The socket probably supports the plug mechanically much better than Aussie ones though.
 

Offline rob77

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #241 on: February 08, 2015, 07:14:17 pm »
The weird ass adapter looks like it has the classic European mains sockets (well, most of Europe)

It's the standard Euro plug alright - called a pig's nose for obvious reasons. The socket is recessed about 2cm with the two holes at the bottom and two springs on the sides for earth, they look pretty strange compared to the flat Aussie type. Also they are not polarised, so Active and Neutral can be on either pin. The socket probably supports the plug mechanically much better than Aussie ones though.

actually it's the Schuko socket  - one of the standard sockets in Europe ;)  the other standard is the French type - but both of the sockets are accepting the Euro-plug.
 

Offline plexus

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #242 on: February 08, 2015, 07:16:51 pm »
I appreciated the review. The board looks ok but yes it was a weird to see all the trimmers and lack of precision parts. seems like they are dialing in the precision. the challenge with that is linearity. but the lack of claimed rating infrastructure nullifies consideration for the product. add in its $190 (is that AUS?) and well you can do well better or even just spend the money on a quality meter with less features.

Thanks to dave for pointing out the features vs quality on this meter. too many companies are padding up the feature set and comprimising quality. the quality aspect is harder to tell unless you open it up and test it.

I don't feel dave was out of line on his comments about this meter. it should irritate you when companies try and pass off a POS like this by padding it with crappy features and charge so much for it. its a shame we have to dig into these things to validate the claims so thanks to dave for doing that for us.

FAIL
 

Offline DanielS

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #243 on: February 08, 2015, 07:52:11 pm »
In which case the multimeter is good enough. The power to my house comes from an outside panel with the meter and a 3x16A breaker. I do not have access to that panel, it belongs solely to the power company. The breaker panel inside my house is thus current limited by the breaker. So, unless I break the law and either open the panel with the meter or break into a substation, I probably would not be able to make the meter explode by accident.
In my case, the building has 100A cartridge fuses for my apartment and while investigating the relatively low outlet voltage, I went in the utility room to measure line voltage directly at the service disconnect / entrance fuse box to rule out building wiring. I did the same thing at my previous apartment but that was to file a complaint with the power company for weak/floating neutral which killed both of my CRT monitors. AFAIK, those fuses are intended to be user-serviceable, so no law is broken by me accessing those terminals.

A few years ago, one of my friends called me in the middle of the night because his mother called him about power freaking out in her apartment with lights flickering wildly on half the circuits whenever the fridge started. It turned out there was a 20-50V drop across one of the 100A entrance fuses. After removing the fuse, it read open (>100Meg) on the ohm range - I definitely was not expecting that from a fuse that can still pass enough current to (sort of) run a fridge and some lights.

Those are the sorts of occasions where someone might end up probing a effectively unprotected circuits without being in an industrial environment.
 

Offline Pentium100

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #244 on: February 08, 2015, 08:05:10 pm »
AFAIK, those fuses are intended to be user-serviceable, so no law is broken by me accessing those terminals.
Different places, different rules. The panel with the meter and a breaker near my house has a seal on it. Also, breakers are used everywhere instead of fuses (fuses can be found in old installations only). This was done probably because nobody replaced blown fuses - just put a piece of wire on the fuse after it blew.
 

Offline Fungus

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #245 on: February 08, 2015, 09:05:49 pm »
Also, breakers are used everywhere instead of fuses (fuses can be found in old installations only). This was done probably because nobody replaced blown fuses - just put a piece of wire on the fuse after it blew.

I thought the traditional 'fix' was a .22 bullet ... they're about the same size as a standard fuse.
 

Offline Pentium100

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #246 on: February 08, 2015, 09:19:39 pm »
I thought the traditional 'fix' was a .22 bullet ... they're about the same size as a standard fuse.
Except that a bullet is way more difficult to find than the fuse, not to mention a piece of wire. It was easier to find bullets during and immediately after WW2, but WW2 happened a log time ago.
 

Offline G7PSK

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #247 on: February 08, 2015, 09:27:08 pm »
There is a good case for banning DVM's in high energy environments and having meters that only read volts and separate meters for amps of the clamp variety, looking through the Fluke range I notice that they do have meters without the amp range.
 

Online jancumps

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #248 on: February 08, 2015, 10:11:30 pm »
AFAIK, those fuses are intended to be user-serviceable, so no law is broken by me accessing those terminals.
Different places, different rules. The panel with the meter and a breaker near my house has a seal on it. Also, breakers are used everywhere instead of fuses (fuses can be found in old installations only). This was done probably because nobody replaced blown fuses - just put a piece of wire on the fuse after it blew.
We're not discussing your apartment here. We're talking about a meter that claims it is safe to be used at points where you personally  are not allowed to go in your apartment.
 

Offline Quarlo Klobrigney

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #249 on: February 08, 2015, 10:33:08 pm »
Slightly off topic,
There is a great invention to thwart dodgy Chinese electronics plugged in to the mains socket, be they glass or ceramic fused, from burning down your house, and it's the:
AFCI http://en.wikipedia.org/wiki/Arc-fault_circuit_interrupter
With these, they detect an arc in its infancy and trip the breaker. I don't know if they are used in the EU & Australia, but they sure do work in here in the US.
Many states specify the use of them in "living areas" as being a mandatory installation. I just got done updating all the wiring from 1939 and up, in my "new" home, and put them on all branch circuits regardless of the mandatory locations.
All wiring was gutted out for scrap and MC armoured cable installed. The MC cable http://www.afcweb.com/product-category/mc-metal-clad-cables/ keeps the critters from chewing on the Romex and see line one above. A little pricy on the refit, but safety first.
The original wiring had seen too many do-it-yourselfers without the simplest of knowledge, including a single circuit that was fed from 2 different breakers in a "loop" configuration. :clap:
My point is if it can be done in a shoddy manner, it will be. China as of late the greatest offender. At least there's a remedy for it in the AFCI. :blah:
« Last Edit: February 08, 2015, 10:50:09 pm by Quarlo Klobrigney »
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Online jancumps

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #250 on: February 08, 2015, 10:43:49 pm »
At least they are protected by your mains fuse. The UNI-T is supposed to work upstream of that tripper, where there is no fuse to protect you from harm :)
 

Offline Corporate666

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #251 on: February 08, 2015, 11:24:56 pm »
A fool and his life are soon parted with?  Darwin award?  Who in their right mind would work with +300V from a Chinese multimeter?  Granted, in the US, we only really have 120, so for us, it's really not much of an issue.   :bullshit:

Fluke meters are made in China too.  And I don't think "Uni-T" is a particularly Chinese sounding name... certainly not like Tenma or the ones that don't even have a name on them.

And I don't think it's unreasonable to expect something labeled to a spec to meet that spec - it's a foundation of marketing and truth in advertising.

In cases where something doesn't meet its spec or isn't of the quality the name or price suggest, how does the consumer find out about that?  They either open it up themselves (in which case they have already purchased it, likely can't then return it and may not be qualified to know what they are looking at).  Or they look to a reviewer who does know what he/she is talking about to review the product.

Sort of like Dave.  :o
It's not always the most popular person who gets the job done.
 

Offline Hydrawerk

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #252 on: February 09, 2015, 12:52:40 am »
UT70A is quite OK for me. It was designed in 2002 or so. But it has some minor problems. https://www.eevblog.com/forum/testgear/uni-t-ut70a-gone-weird/msg255397/#msg255397

Also if you want to replace battery, you have to loosen three screws. For changing the fuse you must loosen seven screws. It is badly designed. The input protection is also rather poor.
« Last Edit: February 09, 2015, 01:06:06 am by Hydrawerk »
Amazing machines. https://www.youtube.com/user/denha (It is not me...)
 

Offline DanielS

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #253 on: February 09, 2015, 01:00:04 am »
I thought the traditional 'fix' was a .22 bullet ... they're about the same size as a standard fuse.
You would have a hard time replacing one of these:
http://uk.farnell.com/cooper-bussmann/non-100/fuse-100a-250v-one-time/dp/2112064
with a bullet - the gap between terminals for the 100A/250V type is almost 6" / 15cm.
 

Offline Monkeh

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #254 on: February 09, 2015, 01:10:02 am »
I thought the traditional 'fix' was a .22 bullet ... they're about the same size as a standard fuse.
You would have a hard time replacing one of these:
http://uk.farnell.com/cooper-bussmann/non-100/fuse-100a-250v-one-time/dp/2112064
with a bullet - the gap between terminals for the 100A/250V type is almost 6" / 15cm.

In Soviet Russia, bullet much bigger than fuse. 12.7mm and 14.5mm rounds aren't that uncommon.
 

Offline Muttley Snickers

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #255 on: February 09, 2015, 04:15:44 am »
These are safer once calibrated, I have the required tool.   :-DD


Muttley
 

Offline Smokey

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #256 on: February 09, 2015, 05:34:53 am »
My point is if it can be done in a shoddy manner, it will be. China as of late the greatest offender. At least there's a remedy for it in the AFCI. :blah:


That is a serious Violation!!  That rock isn't approved to be used as a chair!!  That rock is going to give that guy back problems!!
 

Offline Wytnucls

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #257 on: February 09, 2015, 05:42:23 am »
One major flaw of the 71E, which was overlooked until recently, is the lack of an intermediate amps range (4A).
The true RMS converter doesn't work properly under 10% of range, which means there is a dead zone between 400mA and 1A on this meter. It overreads by 10~15% of measurement.
That's a show stopper on a meter where AC current and power measurement is a major feature.
If the majority of your AC measurements are under 400mA or above 1A, you're OK, otherwise buy something else.
All meters in the 71 range are affected and so is the 61E, with an even larger dead zone of 220mA~1A AC.
Sadly, the new UT181A probably also has a dead zone between 600mA and 1A. UT171 models are OK.

I'm surprised that 71E owners didn't pick this up sooner.
« Last Edit: February 09, 2015, 07:14:58 am by Wytnucls »
 

Offline DanielS

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #258 on: February 09, 2015, 07:10:39 am »
I'm surprised that 71E owners didn't pick this up sooner.
As others have said: if Uni-T is willing to fool around something as serious as safety ratings on a meter that is clearly intended to be connected directly to mains, what else might they be less than honest, if not outright liars, about?

People who buy "inexpensive" Uni-T meters might not have something significantly better or more reputable to compare against. My UT61E is currently my "best" meter and my only True (?) RMS one. One of the first things I did when I got my DS1054Z was a sanity check on that: see if I could get them to agree on the RMS value of voltage across a 0.1 ohm low-side sense resistor powering a 23W CFL lamp, a PC power supply, other stuff I had lying around and a mix of them to produce oddball current waveforms. I could get them to agree within 1% by changing the sampling rate and memory depth on the scope, which is about as good as it is going to be with the DS1000z's DC offset issue.
 

Offline TMM

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #259 on: February 09, 2015, 08:19:48 am »
There are other "more reputable" meters that have blindspots in their ranges too - Agilent U1232A is one.
 

Offline G7PSK

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #260 on: February 09, 2015, 09:22:39 am »
I thought the traditional 'fix' was a .22 bullet ... they're about the same size as a standard fuse.
You would have a hard time replacing one of these:
http://uk.farnell.com/cooper-bussmann/non-100/fuse-100a-250v-one-time/dp/2112064
with a bullet - the gap between terminals for the 100A/250V type is almost 6" / 15cm.
That is a 20mm cannon shell size fuse.
 

Offline Maister

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #261 on: February 09, 2015, 09:23:35 am »
This is really interseting:
I have the UT61E which you are showing towards the end of the video. Mine is only rated 300V CAT III and not 600V CAT IV.
Despite that mine has a better input protection: A bigger HRC fuse for the 10 amps (690V, I1=80kA), 4 MOVs, and 3 PTCs.

Here are the photos of my UT61E:
https://dl.dropboxusercontent.com/u/11083462/DSCN1240.JPG
https://dl.dropboxusercontent.com/u/11083462/DSCN1241.JPG
Professional electronics design engineer living in Hannover, Germany.
 

Offline Stonent

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #262 on: February 09, 2015, 09:28:21 am »
Um, how has no-one noticed the trace going nowhere? 5:44 in the video. Unless this board has plugged vias, which I seriously doubt. Or my eyes are deceiving me, which is more likely.

It's also visible in other peoples pictures in this thread.

They put in an antenna for better Dave reception.  It didn't work.
The larger the government, the smaller the citizen.
 

Offline Wytnucls

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #263 on: February 09, 2015, 09:36:50 am »
There are other "more reputable" meters that have blindspots in their ranges too - Agilent U1232A is one.
That's pretty obvious with the lack of a mA range on the meter and plenty warning text : 'DC/AC current range of 0.6 mA to 300 mA is not measureable on the U1232A and U1233A models'.
More insidious on the 71E. Even Dave, with his vast experience, didn't latch onto that. Mentions of glass fuses always elicit more gasps from the audience.
 

Offline EEVblog

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Re: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)
« Reply #264 on: February 09, 2015, 09:38:47 am »
More insidious on the 71E. Even Dave, with his vast experience, didn't latch onto that. Mentions of glass fuses always elicit more gasps from the audience.

I wasn't reviewing the meter, it was a teardown. I had barely touched it.