Author Topic: UNI-T UT61E Multimeter teardown photos.  (Read 719176 times)

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Offline wasyoungonce

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Re: UNI-T UT61E Multimeter teardown photos.
« Reply #1025 on: June 19, 2018, 11:03:59 am »
There are different versions with different pots ( dividor reference networks)so ensure you replace the OEM with the same specified value.
I'd forget my Head if it wasn't screwed on!
 

Offline sonny

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Re: UNI-T UT61E Multimeter teardown photos.
« Reply #1026 on: June 19, 2018, 11:19:29 am »
There are different versions with different pots ( dividor reference networks)so ensure you replace the OEM with the same specified value.
Hello,
Thanks for your message. As far as I know VR1 is the same 3296X pot with 2k value for all UT61E in production (just different brands). Interesting enough in the manual says 1k for VR1.
 

Offline joeqsmith

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Re: UNI-T UT61E Multimeter teardown photos.
« Reply #1027 on: June 20, 2018, 10:56:32 am »
In Nov 2016, I had measured the temperature drift of my new UT61E and made a video were I compensated it.  I had also changed out the one trimmer pot.  Someone had asked about long term drift and I mentioned I would start collecting some data from mine.  It sounds like some people are seeing a lot of drift.  I can't help but wonder if this is operator or the meter.   

Anyway, here is some data from my UT61E after the temperature compensation taken on 11-21-16:
1mV: 1.02
1V: 1.0001
10V: 10.002
1nF: 1.003

I have had the meter apart a few times since then to make other modifications to it including the larger shunt for measuring 20A and attempting to improve the burden voltage in the uA range.  However, I have been careful not to adjust the trimmers that would effect this little study. 

You can see the in the mV range the meter appears to have a change of 30uV.  However, it's way to small of a change to hang my hat on and way too little time has passed.   I would expect the meter would be fairly stable.  Maybe people are using an unstable source to look at drift?

It's been another 6 months since I last measured the drift of my UT61E.   


 
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Offline ziplock9000

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Re: UNI-T UT61E Multimeter teardown photos.
« Reply #1028 on: June 21, 2018, 03:21:23 am »
Speaking of blow ups, I had a major brain fart yesterday... I had my UT61E in "A" position, test leads connected to COM and 10A sockets.  One test lead was connected to negative terminal of a fully charged 12V car battery, and then I attempted to touch the positive battery terminal with the other test lead.  I only touched the positive terminal for a split second since I saw a spark at the positive terminal and heard the DMM beep.

The DMM still measures voltage, but not current on the 10A socket.  Hopefully I only blew the fuse and nothing else.  Is BS1362 the correct replacement fuse?  I have the Chinese version, not the German version.

Thanks!
You say German version.. Isn't it a European version because the reason it's different is due to European safety laws?
 

Offline ProBang2

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Re: UNI-T UT61E Multimeter teardown photos.
« Reply #1029 on: June 22, 2018, 05:28:28 am »
You say German version.. Isn't it a European version because the reason it's different is due to European safety laws?

Perhaps that is the case because:
  • It first popped up in Germany.
  • It seems to be like unobtanium, except from german suppliers.
  • It is labeled with the "GS" sign and independent tested from the german TÜV.

Actually it should be even the "European Version". In Germany this version was necessary because of product liability.
Regarding the european laws - let me make some examples, please:
  • A 9 year old boy from New York send a populated PCB to his grandpa in Berlin. The box includes the written message "Look! My first soldered PCB."
    - No Problem with the import to europe. It is clearly not commercial or available in higher counts.
     
  • A clever guy sells a self developed and manufactured special measurement device from Australia to europe. But sometimes the import was denied...
    - That is maybe because he does not marked his device with the "CE" sign. Every commercial product must be (at least) marked with this. With this sign the manufacturer assures that his product is made under consideration of the EU regulations. (Yes! That includes correct CAT ratings on DMM´s too! But remember: The manufacturer labels the products... Hence the "CE" sign is practically useless.)
     
  • Hans Schmidt from Munich ordered a CAT IV rated DMM direct from China. He used it in a CAT IV enviroment. The DMM broke down, he is now very crispy.
    - Because he is himself the importer of the DMM, there is no product liability involved. And there is no way to sue a manufacturer in China...
     
  • His brother, Peter, ordered the same DMM for himself. After his brother was well done and crunchy he selled his own device. Now is the buyer heavy injured by electrocution under similar circumstances as Hans.
    - Depending of the local laws is the importer (Peter!) legally responsible. Even as a private person.
     
  • Same case as 3, except: Hans bought the DMM from a german supplier (like Distrelec, Pollin etc.).
    - The supplier as the importer is full liable that the product he sells is fullfilling the claimed characteristics. Therefor he is fully legally responsible.
     

I hope, I could made it clear. I know: Too much waffling...   :blah: :blah: :blah:
 
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Offline ziplock9000

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Re: UNI-T UT61E Multimeter teardown photos.
« Reply #1030 on: June 22, 2018, 08:37:06 am »
That makes sense, thanks  ;D
 

Offline sonny

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Re: UNI-T UT61E Multimeter teardown photos.
« Reply #1031 on: July 03, 2018, 08:14:07 pm »
It's been another 6 months since I last measured the drift of my UT61E.   
You had temperature compensation inside the unit, right?
 

Offline rollatorwieltje

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Re: UNI-T UT61E Multimeter teardown photos.
« Reply #1032 on: July 26, 2018, 01:15:31 pm »
Just thought I'd share this, don't leave your UT61E in the sun, the screen will turn black. After cooling it down it recovered. My Fluke 101 and a cheapo Ohmeron mt488e didn't have this "problem".
 

Offline ziplock9000

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Re: UNI-T UT61E Multimeter teardown photos.
« Reply #1033 on: July 26, 2018, 02:37:28 pm »
That's not specific to the UT61E, it happens to almost all LCD displays
 

Offline joeqsmith

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Re: UNI-T UT61E Multimeter teardown photos.
« Reply #1034 on: July 26, 2018, 10:57:21 pm »
It's been another 6 months since I last measured the drift of my UT61E.   
You had temperature compensation inside the unit, right?
Sorry, I missed your question.   The meter has had several modifications done to it at this point.  Yes, I did modify the reference to attempt to make it more stable with temperature.  Originally it was one of the least stable meters I looked it.   It's actually more stable now than many of the meters I have.  I also changed out the 10T trimmer pot while I was at it, assuming this was the major contributor.  It did not turn out to be the problem and I just left the new part in there. 
 
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Offline jackobo

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Re: UNI-T UT61E Multimeter teardown photos.
« Reply #1035 on: August 01, 2018, 10:11:16 am »
joeqsmith: could you please  specify, what exactly nominal of the resistor you put in between C41-42 in your Part 1 of the robustness video to prevent EMC shock to the main chip?thanks
 

Offline uncle_sem

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Re: UNI-T UT61E Multimeter teardown photos.
« Reply #1036 on: August 24, 2018, 01:26:59 pm »
spare LCDs for ut61e here: https://aliexpress.com/item/UNI-T-UT61E-dedicated-LCD-screen-LCD-size-65mm-43-mm/32906907573.html
got one (well, i'm ordered 3pcs) and very happy about it. I guess it's even little better than original one
 
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Offline TheGrave

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Re: UNI-T UT61E Multimeter teardown photos.
« Reply #1037 on: February 21, 2019, 04:07:01 am »
Wondering if these can be clipped on the test leads of UT61E, any clue?

https://www.banggood.com/DANIU-2Pcs-2000V-30A-Crocodile-Alligator-Folders-Safety-Test-Clips-For-4mm-Shrouded-Banana-Plug-p-1157631.html?rmmds=search&cur_warehouse=CN

Not sure if a solid connection can be made, perhaps they are for a different purpose but I like to misuse products :)  Otherwise plenty of good reviews on Daniu cables by HKJ...
 

Offline HKJ

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Re: UNI-T UT61E Multimeter teardown photos.
« Reply #1038 on: February 21, 2019, 06:54:12 am »
Wondering if these can be clipped on the test leads of UT61E, any clue?

https://www.banggood.com/DANIU-2Pcs-2000V-30A-Crocodile-Alligator-Folders-Safety-Test-Clips-For-4mm-Shrouded-Banana-Plug-p-1157631.html?rmmds=search&cur_warehouse=CN

Not sure if a solid connection can be made, perhaps they are for a different purpose but I like to misuse products :)  Otherwise plenty of good reviews on Daniu cables by HKJ...

They cannot, they are for 4mm unshrouded banana plugs..
 

Offline honeybadger

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Re: UNI-T UT61E Multimeter teardown photos.
« Reply #1039 on: March 27, 2019, 01:21:19 pm »
Hi, my new UT61e just arrived and I must say I am confused about voltage ranges.

at "mV" DC range it says "OL" when nothing is connected.
at "mV" DC range it measure "0.20mV" even with terminals shorted with thick wire with gold plated banana plugs.
at "V" DC range it masure "0.0020V" with shorted terminals.


This shouldn't be happening I guess. With all my others DMMs when voltage is selected and nothing is connected it shows something but definitely not "OL" and when I short the terminals it shows something really close to zero - definitely not 20 digits above zero.

Is this enough for a warranty claim?

edit: accuracy is suppose to be:
220mV +/- (0.1%+5)
2.2V / 22V / 220V +/- (0.1%+2)

So for 220mV range it is suppose to show 0.05mV in worst case scenario -> offset is 400% off.
For 2.2 range it is suppose to show 0.0002 in worst case scenario -> offset is 1000% off.

edit 2:
It measures off by 0.4V at 30V DC. Jesus Christ how is this possible with a new multimeter?  5USD noname is more accurate.
« Last Edit: March 27, 2019, 01:47:42 pm by honeybadger »
 

Offline stj

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Re: UNI-T UT61E Multimeter teardown photos.
« Reply #1040 on: March 31, 2019, 11:10:04 am »
short it with a paperclip, your cable is a recieving antenna - where i live, i power a string of christmas leds dimly with 2m of cable with a cap on the end!!!
 

Offline joeqsmith

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Re: UNI-T UT61E Multimeter teardown photos.
« Reply #1041 on: March 31, 2019, 03:40:18 pm »
at "mV" DC range it says "OL" when nothing is connected.
at "mV" DC range it measure "0.20mV" even with terminals shorted with thick wire with gold plated banana plugs.
at "V" DC range it masure "0.0020V" with shorted terminals.


edit: accuracy is suppose to be:
220mV +/- (0.1%+5)
2.2V / 22V / 220V +/- (0.1%+2)

So for 220mV range it is suppose to show 0.05mV in worst case scenario -> offset is 400% off.
For 2.2 range it is suppose to show 0.0002 in worst case scenario -> offset is 1000% off.


It could be my simpleton math skills ...
I assume it's of full scale, so +270uV?    200uV seems in spec.
For 2.2 the volt range, +2.7mV?  2.0mV seems in spec.

Mine has been modified and may not represent how a stock meter would behave.   With no leads attached, selecting the mV function, it will display OL and slowly drop.   Of the meters I have looked at, this meter was one of the worst for temperature drift.  One of the things I had done was compensate mine.  I would have no way of knowing the tolerance of your 30V supply but I have been tracking the drift.  I have attached today's data.  The voltages are checked against a Fluke 731B reference standard.   The 100ohm is a 0.01% 2ppm Caddock part.   Capacitor is a COG.   

Attached picture shows how badly this meter has been treated. 

 
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Offline honeybadger

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Re: UNI-T UT61E Multimeter teardown photos.
« Reply #1042 on: March 31, 2019, 10:52:52 pm »
stj: I will try to make a shorting adapter for future use - two gold bananas and few cm of solid copper wire. But how exactly is the "antenna problem" relevant to DC measurements? I mean none of my other multimeters has this "antenna issue" at DC V ranges.

joeqsmith: correct me if I am wrong - when meter accuracy is described as AA% + BBD this means:
"AA" is linearity error from measured value (not from a full range) described as percentage error from measured value
"BB" is a zero offset error described as count of least significant digits at current range at meters resolution.

So when the leads are shorted the linearity error is suppose to be zero and nothing else and only zero offset plays role here -> thus 200uV offset at 220mV range is ridiculously high.


edit: Brymen BM867s is on the way - thank you for your review of 869. I will try to save this sick UT and give it to someone else.

edit2: something else puzzles me. It shows different value when I switch the polarity of the leads. For example 20.35V at one polarity and -20.10V at reverse polarity - both at 20.0V DC.

edit3: my 30V power supply was checked with UT50E (which I know it measures correctly) and when PSU shows "30.00V" and UT50E (connected in paralell to UT61E) shows "30.02V" I am pretty confident it is really close to 30V.
« Last Edit: March 31, 2019, 11:39:26 pm by honeybadger »
 

Offline joeqsmith

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Re: UNI-T UT61E Multimeter teardown photos.
« Reply #1043 on: March 31, 2019, 11:42:59 pm »
joeqsmith: correct me if I am wrong - when meter accuracy is described as AA% + BBD this means:
"AA" is linearity error from measured value (not from a full range) described as percentage error from measured value
"BB" is a zero offset error described as count of least significant digits at current range at meters resolution.

As I stated, I assumed it was percent of full scale.   It could be percent of reading.  It should be in the manual but I don't always see it defined.   If it is of reading, yours is really out of whack.   
 
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Offline honeybadger

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Re: UNI-T UT61E Multimeter teardown photos.
« Reply #1044 on: March 31, 2019, 11:52:37 pm »
I guess when it is meant from full range only percentage value is stated - like for an analog meter.

For this DMM it is from reading:


I will confront Bangood with this issue.
 

Offline TheNewLab

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Re: UNI-T UT61E Multimeter teardown photos.
« Reply #1045 on: April 01, 2019, 12:21:12 am »
Hi, my new UT61e just arrived and I must say I am confused about voltage ranges.

at "mV" DC range it says "OL" when nothing is connected.
at "mV" DC range it measure "0.20mV" even with terminals shorted with thick wire with gold plated banana plugs.
at "V" DC range it masure "0.0020V" with shorted terminals.


This shouldn't be happening I guess. With all my others DMMs when voltage is selected and nothing is connected it shows something but definitely not "OL" and when I short the terminals it shows something really close to zero - definitely not 20 digits above zero.

edit: accuracy is suppose to be:
220mV +/- (0.1%+5)
2.2V / 22V / 220V +/- (0.1%+2)

So for 220mV range it is suppose to show 0.05mV in worst case scenario -> offset is 400% off.
For 2.2 range it is suppose to show 0.0002 in worst case scenario -> offset is 1000% off.
how is this possible with a new multi-meter ?  5USD noname is more accurate.

The "OL" doesn't make sense to me. I learned from an electrician who says he only gets DMMs that when nothing is connected with or without probes attached the voltage numbers drift all over the place. He calls it ghost voltage and it tells him if an electrical circuit is completely open. Some of my DMMs do that others don't they just show 0.0000 when nothing is connected with or without probes attached.

whoa wait! I had tested a meter in voltage mode probes attached not connected to anything just measuring the air in different places and different rooms. I could swear the voltage changed in the air differently from room-to--room..I, we were drunk as hell though!! :popcorn::-DD
« Last Edit: April 01, 2019, 12:30:28 am by TheNewLab »
 

Offline TheNewLab

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Re: UNI-T UT61E Multimeter teardown photos.
« Reply #1046 on: April 01, 2019, 12:39:03 am »
Joe, That photo seems within specs, but any drift at all I would think should not happen at all.
I have noticed that when manufacturers include in their calibration sheet both temp and RH% when tested. Never have been sure about that. i mean you buy a multimeter calibrated in Cupertino and you live in Denver. both altitude and humidity is way different.




Mine has been modified and may not represent how a stock meter would behave.   With no leads attached, selecting the mV function, it will display OL and slowly drop.   Of the meters I have looked at, this meter was one of the worst for temperature drift.  One of the things I had done was compensate mine.  I would have no way of knowing the tolerance of your 30V supply but I have been tracking the drift.  I have attached today's data.  The voltages are checked against a Fluke 731B reference standard.   The 100ohm is a 0.01% 2ppm Caddock part.   Capacitor is a COG.   

Attached picture shows how badly this meter has been treated.
[/quote]

I have watched your videos on modding multimeters.  I wondered about is, if changing out MOVs, didn't the calibration change?
 

Offline honeybadger

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Re: UNI-T UT61E Multimeter teardown photos.
« Reply #1047 on: April 01, 2019, 01:18:32 am »
 TheNewLab: the "OL" at mV range might be some residual voltage in the input circuitry capacitance. When it discharge to zero - that is fine with me. My meter shows "OL" indefinitely.

"Ghosts voltages" are also acceptable - there is a high impedance input... it can change by itself. But there is no place for these ghosts when leads are shorted.

The "OL" at mV range gave me an idea. There must be some current leaking into the ADC input - probably after the 10M resistor.
This would clarify:
- "OL" at mV range (current is leaking into ADC and overloading it, it is "grounded" when anything is connected)
- high zero offset
- asymmetry of measurement when switching polarity

Do I understand the schematic correctly (picture attached)?
Am I dreaming or there is no external voltage clamping after the 10M resistor?!


 

Offline joeqsmith

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Re: UNI-T UT61E Multimeter teardown photos.
« Reply #1048 on: April 01, 2019, 10:17:31 am »
Joe, That photo seems within specs, but any drift at all I would think should not happen at all.
....
I have watched your videos on modding multimeters.  I wondered about is, if changing out MOVs, didn't the calibration change?

If only zero drift were even possible!   I'm not suggesting you couldn't buy a really low end meter that never changes one place with temp and time...  A meter that can only resolve down to a volt can't display nV of drift.   Check a manual for some higher end equipment and see what they list for temperature requirements.

If you watched those videos, I would imagine there was some data collected before adding the MOVs.   I would assume the MOVs would change the baseline capacitance but I would null that out before making a measurement.   
 
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Offline joeqsmith

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Re: UNI-T UT61E Multimeter teardown photos.
« Reply #1049 on: April 01, 2019, 10:23:01 am »
Am I dreaming or there is no external voltage clamping after the 10M resistor?!
If you download the datasheet for the controller, you may gain some insight as to why this is. 

Be aware that the schematic you show may not match your meter. 


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