Author Topic: EEVblog #712 - Uni-T UT71E Multimeter (Why Uni-T Meters Suck)  (Read 155770 times)

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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.

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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.

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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.

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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
Youtube channel:Taking wierd stuff apart. Very apart.
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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.

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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.
"Yeah, but no, but yeah, but no..."
 

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 »
 


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