I checked my Extech 330's manual. It does check Hz% at full mains. Then proceeded to check the mains and worked flawlessly.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 Barry
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. ;)
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.
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.
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 am aware that most UNI-T frequency counters on multimeters are limited to 30V of input voltage.
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 specifications’ usually called as misuse and voids the Warranty.
I can not blame the company if they did not respond.
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.
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.
I think there are major design differences in between the model numbers of their lines and Uni-T has very poorly documented them.
The manuals for the 90A and 90C are different as they are fairly different in terms of features / functionality i.e. 2000 vs 4000 count, manual vs auto ranging and battery vs solar power.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.By the way Martin, did the 90 C's printed manual differ from the 90 A's, or is the manual like the 61 series and one book covers the entire line?
Martin did you revive it ? ;D (on your latest video it looks that way)
Martin did you revive it ? ;D (on your latest video it looks that way)
Will you share the repair tip with the planet ? :)
And don't think we haven't noticed that you are color coordinating your shirts with the color of the multimeter rubber holster. Red shirt for UT90C and orange for your solar clock while talking about the 1272A logging capabilities. ;)
And don't think we haven't noticed that you are color coordinating your shirts with the color of the multimeter rubber holster. Red shirt for UT90C and orange for your solar clock while talking about the 1272A logging capabilities. ;)
Cheeky man! :PAnd don't think we haven't noticed that you are color coordinating your shirts with the color of the multimeter rubber holster. Red shirt for UT90C and orange for your solar clock while talking about the 1272A logging capabilities. ;)
I do not have comments about the t-shirts especially when they do not have the brand logo on them.
But he was hugging the red holsters with an enigmatic joy.
Does he hide anything from us? Time will tell. ;D ;D ;D
One last try?
I watched the follow up video on the UT90C, but I cannot tell what the broken UT90C displays when it is on ohms mode.
Does it flash 0.0000 or show 0L?
It shows 0.0000 on ohms.
Thanks very much for the offer...I'll try get some hi-def photos up over the weekend if possible.It shows 0.0000 on ohms.
I noticed the volts reading is also 0.000. With your ohms reading 0.000, it almost looks like the input jacks, COM and voltage, are shorted together?
In any working multimeter, if you put the probes together you would get 0.000V and 0.000 ohms (or close to it). When the probes are apart, you should get a little bit of ghost voltage for volts (minor fluctuation) range and of course 0L for ohm range.
So there might be a shorted component somewhere? Anyway, if you have time, post the photos. I will take a look to see if any component is the likely suspect.
It shows 0.0000 on ohms.
I noticed the volts reading is also 0.000. With your ohms reading 0.000, it almost looks like the input jacks, COM and voltage, are shorted together?
In any working multimeter, if you put the probes together you would get 0.000V and 0.000 ohms (or close to it). When the probes are apart, you should get a little bit of ghost voltage for volts (minor fluctuation) range and of course 0L for ohm range.
So there might be a shorted component somewhere? Anyway, if you have time, post the photos. I will take a look to see if any component is the likely suspect.
It shows 0.0000 on ohms.
I noticed the volts reading is also 0.000. With your ohms reading 0.000, it almost looks like the input jacks, COM and voltage, are shorted together?
In any working multimeter, if you put the probes together you would get 0.000V and 0.000 ohms (or close to it). When the probes are apart, you should get a little bit of ghost voltage for volts (minor fluctuation) range and of course 0L for ohm range.
So there might be a shorted component somewhere? Anyway, if you have time, post the photos. I will take a look to see if any component is the likely suspect.
It is a little difficult to see due to the low resolution of the photos if they are soldered together, but I believe you. What are the part numbers on the transistors? I'll take a look at the datasheets to see why they may be soldered together?Thanks very much, that video put the transistor testing with the diode function into perspective staight away. The NPN's on the board have a different pin out to the ones I was using as a reference. I'm about to de-solder one of the transistors so I can test it out of circuit and will feedback.
By the way, here is another way to test those transistors using the diode test function (34 second video)
http://www.youtube.com/watch?v=8VK_4gZU__I
You may want to test those 3 transistors again using the above method and on a couple of new transistors.
I just watched your test a transistor and diode video. Great job.
If you are willing to test a bit more, take a high resolution picture of the components underneath the lcd. I can look for their datasheets and see if any of the ICs are shorted. Sometimes VCC will be shorted to GND.
I have more ideas, but obviously since I don't have the board in front of me, I can't just test things when I want to.
BTW, I ran into some Sperry brand multimeters. Sperry is a known name in North America. Their multimeter suspiciously look like Uni-Ts. Even the manuals have the same 30V maximum "warning" when measuring frequency.
http://www.sperryinstruments.com/product/digital-multimeters
Hmm, does this screen look familar?
http://www.sperryinstruments.com/images/applications/dm6400_2_lg.jpg
Here we go.......but take a look at the caps along side the IC....I think they look a little suspect?? Only noticed them in the pictures when posting this...
Here we go.......but take a look at the caps along side the IC....I think they look a little suspect?? Only noticed them in the pictures when posting this...
1) The cap sleeves look all melted somehow.
2) I found the datasheet for FS9721_LP3. I'm reading it now to try and understand how it works.
3) While I do that, I have 3 more things for you to measure. All are resistance readings.
i) Marked in yellow are PTCs. I believe they should all be around 1K ohm from reading the datasheet. You may have to desolder these 3 to get a accurate reading?
ii) R26 (in blue) should be a 10M ohm resistor. Measure this in circuit and verify that it 10M.
iii) R31 (in red) is a 10K SMD resistor. Measure this in circuit and verify that is 10K.
4) BTW, rumor has it that the Fluke 15B and 17B use the same FS9721-LP3 processor. Certainly the specs for the Fluke 15B and 17B match up with the FS9721-LP3 datasheet.
5) A really good SMD soldering video is here
http://www.youtube.com/watch?v=3NN7UGWYmBY
6) Of course Dave Jones also has a 3 part soldering video and demonstrates various techniques for SMD.
Here we go.......but take a look at the caps along side the IC....I think they look a little suspect?? Only noticed them in the pictures when posting this...
1) The cap sleeves look all melted somehow.
2) I found the datasheet for FS9721_LP3. I'm reading it now to try and understand how it works.
3) While I do that, I have 3 more things for you to measure. All are resistance readings.
i) Marked in yellow are PTCs. I believe they should all be around 1K ohm from reading the datasheet. You may have to desolder these 3 to get a accurate reading?
ii) R26 (in blue) should be a 10M ohm resistor. Measure this in circuit and verify that it 10M.
iii) R31 (in red) is a 10K SMD resistor. Measure this in circuit and verify that is 10K.
4) BTW, rumor has it that the Fluke 15B and 17B use the same FS9721-LP3 processor. Certainly the specs for the Fluke 15B and 17B match up with the FS9721-LP3 datasheet.
5) A really good SMD soldering video is here
http://www.youtube.com/watch?v=3NN7UGWYmBY
6) Of course Dave Jones also has a 3 part soldering video and demonstrates various techniques for SMD.
PTC1: 1K
PTC2: 567 ohm...out of circuit
PTC3: 589 ohm...out of circuit
R26: 100 ohm...out of circuit
R31 SMD: 10 M ohm...checked several times...
PTC1: 1K
PTC2: 567 ohm...out of circuit
PTC3: 589 ohm...out of circuit
R26: 100 ohm...out of circuit
R31 SMD: 10 M ohm...checked several times...
Okay, I'm using this datasheet as a reference.
www.ic-fortune.com/upload/Download/FS9721_LP3-DS-20_EN.pdf
With the above, I was using the datasheet's pcb designators (page 19) as described by the various diagrams/figures, but it looks like the UT90C is using a variation.
R31 is good as your 10M ohm resistor. As long as R26 matches the color code for a 100 ohm resistor, it is good.
PTC1 at 1K is good. PTC2 and PTC3 are lower than what I expected (1K) unless they are in series, but I don't think the low values are the cause of the UT90C not working. If one of the PTCs were completely open, then it might explain why the UT90C is not working.
Let me think about this for a few more days. Unless I spot something obvious, I think the FS9721-LP3 might be bad.
I tried going to that link but I get a warning that it's an "attack page"....and might steal my data....odd...
Thanks again for your efforts. I thought it might be something in the main IC....but I would have thought that if that had gone faulty the meter would not display anything "intelligent" at all. I presume it can have a partial failure?
I found this while looking for some infoI love it!! I read the entire advert....the "English" is certainly entertaining....
http://www.amazon.co.uk/VOLTCRAFT-Voltcraft-VC290-DMM/dp/B003A5UGBA
I found this part of the description particularly LOL
"The device is protected with comprehensive safeguards against misuse."
Hey Martin,
I was thinking about your UT90C again and thought you might be inspired by one member's recent blog site. His site is full or repairs and pictures. Highly recommended.
http://mrmodemhead.com/
Q1 and Q2 are switched out for voltage measurements, so even if they failed short it should not affect voltage functions. About the only scenario I can come up with is that the PTC opened up permanently. Or, given that the Hz function feeds the ADP input almost directly, the DMM IC is fried. :(
9V battery voltage TENM ONEM
8.08v 80.7mv 0.0
4.90v 52.6mv 0.0
3.76v 37.5mv 0.0
2.466v 228mv 228mv
Note that in your measurements, TENM and ONEM were the same voltage for 2.466V input. That means the divider was in 1/10 mode. I assume the divider was in 1/100 for the higher voltages (HUNK would be in use instead of ONEM.)So for my own learning again, I went and measured the HUNK
9V battery voltage TENM ONEM HUNK
8.08v 80.7mv 0.0 80.0mv
4.90v 52.6mv 0.0 52.4mv
3.76v 37.5mv 0.0 36.7mv
2.466v 228mv 228mv 0.0
So for my own learning again, I went and measured the HUNKWith those measurements, I think you have proven that the micro-controller is running and performing its auto-ranging task properly. Which implies that it is getting good information from the A/D converter.