Author Topic: UNI-T (UNI-Trend) UT90C review.....I killed it!  (Read 30789 times)

MJLorton

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UNI-T (UNI-Trend) UT90C review.....I killed it!
« on: April 11, 2012, 08:45:57 AM »
The video review of the UT90C solar powered multimeter is being uploaded now.....I killed it during the review!

I will link to the video as soon as it is up....


Cheers.
Martin.
Play, discover, learn and enjoy! (and don't be scared to make mistakes along the way!)

Kiriakos GR

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Re: UNI-T (UNI-Trend) UT90C review.....I killed it!
« Reply #1 on: April 11, 2012, 03:36:14 PM »
Shit happens but the word ....I killed it!  does it translate to damage beyond repair ?

The worst that you can possibly do is to damage the connection of the wires with the solar panel of the dmm. ;)

Barryg41

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Re: UNI-T (UNI-Trend) UT90C review.....I killed it!
« Reply #2 on: April 11, 2012, 06:05:32 PM »
I checked my Extech 330's manual. It does check Hz% at full mains. Then proceeded to check the mains and worked flawlessly.

Cheers Barry

retiredcaps

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Re: UNI-T (UNI-Trend) UT90C review.....I killed it!
« Reply #3 on: April 12, 2012, 12:03:03 AM »
Great review. 

I think the UT90C should have survived because that is a pretty standard test.  It will be interesting to see if your video makes it to Uni-Trend headquarters to see what their response will be. 

edit: Maybe you will get a replacement multimeter like how Kiriakos got a Fluke 28 II after his 87V was bricked by GSM phone.  Or maybe Uni-Trend will send you an updated board version like Fluke did for the 87V rev 11 to Dave?  Their response will speak volumes about how serious they are in this market.

One minor nit because I ran into this problem last year.

On another forum, I always advise newbies never to use continuity as way to test fuses.  The reason is that some multimeters regard something as continuous if the resistance is less than 1800 ohms.  So if the fuse measures 500 ohms the newbie will be led to believe that the fuse is good.

I have a fuse that will beep continuous on my Fluke, where the threshold is less than 25 ohms, but the fuse is bad because it measures 18 ohms.  A good fuse should measure less than 1.0 ohms.

What is even more confusing is that some multimeters have the diode test and continuity test on the same rotary function (like my Fluke 75).  So instead of displaying an ohms reading for continuity, it displays DC volts.  The same 18 ohm fuse reads 0.009 in continuity test.

This is not a problem on the Fluke 115 as the continuity function shows ohms as a reading.
« Last Edit: April 12, 2012, 01:25:00 AM by retiredcaps »

retiredcaps

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Re: UNI-T (UNI-Trend) UT90C review.....I killed it!
« Reply #4 on: April 12, 2012, 01:03:43 AM »
By the way, take the UT90C apart so we can see the front side of the pcb.  Maybe there are some components that you can test and find out what the problem is.

kodai

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Re: UNI-T (UNI-Trend) UT90C review.....I killed it!
« Reply #5 on: April 12, 2012, 03:16:39 AM »
I'm very disappointed with this little meter.  Yeah, I can understand the technicality thing on your part of not reading the manual about the switching of ranges while measuring something, but no frequency above 30v?  I've been debating getting that little guy for months, but now that I've how fragile it is I think I'm gonna skip it.  Maybe the next version will improve upon the design.  I mean, I hardly ever work with anything over 30v, so that wouldn't be a real issue for me.  Something about it just seems too fragile to me.  Oh well. 

Great partial review though.  On a side note about you're reference tests:  is your lab at the same temp as the ratting listed on the test boards?  That could throw the tests off a digit or two if its a few degrees off.  Plus the ambient temps in the testing area under your lighting could be warmer still.  Maybe you could tell us your lab temp on each video vs the nominal rated reference board tests.  Of course with all those variables, plus the meters spec sheet over at Uni-T's site show it to be a pretty accurate meter under your partial test. 

Thanks for giving us what little real world info you could on the 90c, it help me make my mind up about it.   :)   

MJLorton

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Re: UNI-T (UNI-Trend) UT90C review.....I killed it!
« Reply #6 on: April 12, 2012, 04:07:19 AM »
I checked my Extech 330's manual. It does check Hz% at full mains. Then proceeded to check the mains and worked flawlessly.

Cheers Barry
Handy feedback...it's a little crazy that we'd have to check the manuals to ensure "general" measurements we are taking are within spec of what the multimeter can do....but this little episode will certainly make me look a little closer at the cheaper meter specs before testing.

Cheers,
Martin.
Play, discover, learn and enjoy! (and don't be scared to make mistakes along the way!)

MJLorton

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Re: UNI-T (UNI-Trend) UT90C review.....I killed it!
« Reply #7 on: April 12, 2012, 04:09:58 AM »
Shit happens but the word ....I killed it!  does it translate to damage beyond repair ?

The worst that you can possibly do is to damage the connection of the wires with the solar panel of the dmm. ;)

Indeed it does! I will take a closer look to see if there is anything obvious that can be fixed.....but at lease the cap and solar panel are in one piece ;-)
Play, discover, learn and enjoy! (and don't be scared to make mistakes along the way!)

MJLorton

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Re: UNI-T (UNI-Trend) UT90C review.....I killed it!
« Reply #8 on: April 12, 2012, 04:23:00 AM »
Great review. 

I think the UT90C should have survived because that is a pretty standard test.  It will be interesting to see if your video makes it to Uni-Trend headquarters to see what their response will be. 

edit: Maybe you will get a replacement multimeter like how Kiriakos got a Fluke 28 II after his 87V was bricked by GSM phone.  Or maybe Uni-Trend will send you an updated board version like Fluke did for the 87V rev 11 to Dave?  Their response will speak volumes about how serious they are in this market.

One minor nit because I ran into this problem last year.

On another forum, I always advise newbies never to use continuity as way to test fuses.  The reason is that some multimeters regard something as continuous if the resistance is less than 1800 ohms.  So if the fuse measures 500 ohms the newbie will be led to believe that the fuse is good.

I have a fuse that will beep continuous on my Fluke, where the threshold is less than 25 ohms, but the fuse is bad because it measures 18 ohms.  A good fuse should measure less than 1.0 ohms.

What is even more confusing is that some multimeters have the diode test and continuity test on the same rotary function (like my Fluke 75).  So instead of displaying an ohms reading for continuity, it displays DC volts.  The same 18 ohm fuse reads 0.009 in continuity test.

This is not a problem on the Fluke 115 as the continuity function shows ohms as a reading.

Has to be said....I think I would be very lucky if Uni-Trend did respond in any way as this meter would not be a key focus of many folks...but, having said that, it seems the UT61E has the same limitation...and that would have a larger following. I'll see if I can get some feedback from them.

Thanks for the feedback on the continuity...very valid point. The resistance threshold of the continuity testing has caught my eye in some of the specs but I had not consciously considered the importance...might be a good point to cover in a video....just added it to the "to do" list. 

Thanks for posting,
Martin.
Play, discover, learn and enjoy! (and don't be scared to make mistakes along the way!)

MJLorton

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Re: UNI-T (UNI-Trend) UT90C review.....I killed it!
« Reply #9 on: April 12, 2012, 04:25:04 AM »
By the way, take the UT90C apart so we can see the front side of the pcb.  Maybe there are some components that you can test and find out what the problem is.

Yup, will give it a bash...if no joy...I have a good use planned for some of the parts!
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MJLorton

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Re: UNI-T (UNI-Trend) UT90C review.....I killed it!
« Reply #10 on: April 12, 2012, 05:04:31 AM »
I'm very disappointed with this little meter.  Yeah, I can understand the technicality thing on your part of not reading the manual about the switching of ranges while measuring something, but no frequency above 30v?  I've been debating getting that little guy for months, but now that I've how fragile it is I think I'm gonna skip it.  Maybe the next version will improve upon the design.  I mean, I hardly ever work with anything over 30v, so that wouldn't be a real issue for me.  Something about it just seems too fragile to me.  Oh well. 

Great partial review though.  On a side note about you're reference tests:  is your lab at the same temp as the ratting listed on the test boards?  That could throw the tests off a digit or two if its a few degrees off.  Plus the ambient temps in the testing area under your lighting could be warmer still.  Maybe you could tell us your lab temp on each video vs the nominal rated reference board tests.  Of course with all those variables, plus the meters spec sheet over at Uni-T's site show it to be a pretty accurate meter under your partial test. 

Thanks for giving us what little real world info you could on the 90c, it help me make my mind up about it.   :)

I don't really work with anything over 30v either but it would leave a nagging feeling inside if I always had to be careful about that limitation....fragile is a good way to describe it!

My goodness....I've come to realise that reference tests, calibration, etc are a hot topic and quite a science.....

We happen to be having cooler weather now so it was about 21C in my "lab" and the temperature the DMMCheck and PentaRef  were calibrated at was 70F (about 21.111C). The documentation quotes as follows: "To maintain 0.01% accuracy, make sure that the ambient temperature is within 14 degrees F (about 7 C) of the calibration temperature. The reference voltage typically drifts approximately 15uV / degree F."

The lighting I have above the test boards is LED so not much heat there...but I'll check that to make sure. The spec of the UT90C in this case is so "coarse" compared to the reference that in this case I was not concerned about environmentals having an effect. But....it is none the less an important point. This becomes more critical with the higher count and accuracy meters and I'm hoping to get another reference source that has a little more flexibility and robustness....so watch this space.

Thanks for posting,
Martin.
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Kiriakos GR

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Re: UNI-T (UNI-Trend) UT90C review.....I killed it!
« Reply #11 on: April 12, 2012, 11:22:04 AM »
quick note : my first response above, was at the time that the video was not there yet = no video to watch.
I am downloading it now, so to see what really happened.   

About the subject : response of UNI-T
Someone should inform them first, so to get an response.





Kiriakos GR

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Re: UNI-T (UNI-Trend) UT90C review.....I killed it!
« Reply #12 on: April 12, 2012, 03:12:47 PM »
I am aware that most UNI-T frequency counters on multimeters are limited to 30V of input voltage.
Simply because they were made to count low power signals.

Even my Japanese made dedicated frequency counter (made by LEADER),
Have the specificationsí of 150 MHz, 20V PP Max input.
And it is a great instrument about verifying the accuracy of a PLL synthesizer (low power transmitter). 
The frequency counter circuitry is not protected in any way about over voltage in any device.

The assumption that every multimeter or dedicated frequency counter should be capable to measure frequency of Mains it is a wild one.
But no one can blame an IT specialist because he made such a wild assumption.
   
UNI-T deserves to be blamed because of their tiny in size Users Manuals and the tiny small print in them.
Reading those manuals with the use of binoculars is always a great idea. LOL

Retiredcaps@ 
The violation of written specificationsí usually called as misuse and voids the Warranty.
I can not blame the company if they did not respond.

If the long distance seller haves the good will to replace the device by adsorbing the loss so to keep the customer happy, this is a hypothetical suggestion that Martin should explore too.   

   

retiredcaps

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Re: UNI-T (UNI-Trend) UT90C review.....I killed it!
« Reply #13 on: April 13, 2012, 01:48:12 AM »
I am aware that most UNI-T frequency counters on multimeters are limited to 30V of input voltage.

I don't have any Uni-T's multimeters, but I'm totally surprised at this limitation.  I have NO background or formal training in electronics/electricity at all.

About 6 months ago, I considered getting a UT61E due to the positive reviews, but I managed to find some used Flukes for some very reasonable prices.  Since they are used, I test every function to ensure they work and I use mains to test out the HZ function.

I even had a $50 Amprobe AM-60 with HZ capabilities and plugged the AM-60 into mains without problems.

Quote
The assumption that every multimeter or dedicated frequency counter should be capable to measure frequency of Mains it is a wild one.
But no one can blame an IT specialist because he made such a wild assumption.

Retiredcaps@ 
The violation of written specificationsí usually called as misuse and voids the Warranty.
I can not blame the company if they did not respond.

I agree that the limitation is documented and that this is user error.  However, this is a good opportunity for Uni-T to make their multimeters more robust.  I'm not a multimeter design engineer, but perhaps they can make the HZ fail in a way that doesn't completely brick the multimeter.

I mean we all make mistakes when we are distracted, tired, and/or forgetful so multimeters manufacturers should take this into consideration and try to protect the user and the equipment.

Let's say that Martin did notice the HZ voltage limitation and didn't kill the UT90C, but 3 weeks later he lends this multimeter to a friend and he decides to test HZ on mains.  Does Martin need to put a warning label above the HZ symbol?
« Last Edit: April 13, 2012, 03:58:37 AM by retiredcaps »

retiredcaps

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Re: UNI-T (UNI-Trend) UT90C review.....I killed it!
« Reply #14 on: April 13, 2012, 03:11:07 AM »
Okay, here is something interesting.  The manual for the UT61 series at

http://www.uni-trend.com/manual2/UT61English.pdf

clearly says on page 32 not to have more than 30V input.  This is the same warning as the UT90C.

So why does the UT61D in Dave's $99 shootout part 2 correctly show 50HZ in the mains voltage ohms overload test?  You can clearly see this at 22:12 to 22:37.  You can see him switch from ACV to HZ without disconnecting the mains and the UT61D survived.