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

[TMM]

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.

[Yago]

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

[G7PSK]

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.   

[0b01010011]

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.

[rob77]

i'm glad i didn't buy the uni-turd meter 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.

[Horstelin]

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

[EEVblog]

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.

[EEVblog]

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.

[EEVblog]

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.

[FrontSideBus]

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!

[firewalker]

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.

[R_Gtx]

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.

[G7PSK]

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.

[Fungus]

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

[eV1Te]

... 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.

[timb]

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!)


Sent from my Smartphone

[Owen]

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.

[eV1Te]

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)

[Yago]

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.

[Quarlo Klobrigney]

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)

[G7PSK]

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.

[DanielS]

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.

[Lightages]

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.

[mariush]

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.

[Nerull]

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.