Author Topic: UT139E and UT139S Digital Multimeters - no discussion?  (Read 13221 times)

0 Members and 2 Guests are viewing this topic.

Offline Travie21

  • Contributor
  • Posts: 9
  • Country: ph
Re: UT139E and UT139S Digital Multimeters - no discussion?
« Reply #25 on: January 31, 2019, 03:03:37 am »
Hello guys. Can I ask what's the problem of my meter? Its UT139E. I accidentaly plugged it on AC while its on resistance mode. I can still read low resistances from 1-1kohm I guess, but not be able to read over Mega Ohm. Continuity still works fine and diode test. The capacitance does not work, its stocked on 0.000 micro fara unlike before it starts on nano farad. Ac and DC voltage still works, but DCmV is on OL but indicating a high voltage on the corner of the meter. NCV does not also work now. I checked the board and see no burned or any signs of visual damage on the components. I also checked the fuses and still works fine. Hope you can help me guys.
 

Offline Fungus

  • Super Contributor
  • ***
  • Posts: 10790
  • Country: 00
Re: UT139E and UT139S Digital Multimeters - no discussion?
« Reply #26 on: January 31, 2019, 07:20:14 am »
Hello guys. Can I ask what's the problem of my meter? Its UT139E. I accidentaly plugged it on AC while its on resistance mode. I can still read low resistances from 1-1kohm I guess, but not be able to read over Mega Ohm. Continuity still works fine and diode test. The capacitance does not work, its stocked on 0.000 micro fara unlike before it starts on nano farad. Ac and DC voltage still works, but DCmV is on OL but indicating a high voltage on the corner of the meter. NCV does not also work now.

Sounds like you zapped it.

I checked the board and see no burned or any signs of visual damage on the components. I also checked the fuses and still works fine. Hope you can help me guys.

Damage isn't always visible, fuses are only used on current ranges.
 

Online HKJ

  • Super Contributor
  • ***
  • Posts: 1242
  • Country: dk
    • Tests
Re: UT139E and UT139S Digital Multimeters - no discussion?
« Reply #27 on: January 31, 2019, 07:24:16 am »
A guess is that you have zapped the input protection transistor pairs. There can be a couple of these pairs.
 

Offline Fungus

  • Super Contributor
  • ***
  • Posts: 10790
  • Country: 00
Re: UT139E and UT139S Digital Multimeters - no discussion?
« Reply #28 on: January 31, 2019, 08:29:56 am »
Today's lesson: Don't use non-CAT-rated muiltimeters on AC mains.

(in fact, don't use any multimeters on mains if you can avoid it, try plugging in in a lamp, they tell no lies)

This is a real man's mains tester:


 

Offline Hydrawerk

  • Super Contributor
  • ***
  • Posts: 2392
  • Country: 00
Re: UT139E and UT139S Digital Multimeters - no discussion?
« Reply #29 on: January 31, 2019, 01:47:17 pm »
Hello guys. Can I ask what's the problem of my meter? Its UT139E. I accidentaly plugged it on AC while its on resistance mode.
Was it 230VAC or 2000VAC from a microwave oven transformer??
« Last Edit: January 31, 2019, 01:49:14 pm by Hydrawerk »
Amazing machines. https://www.youtube.com/user/denha (It is not me...)
 

Offline Travie21

  • Contributor
  • Posts: 9
  • Country: ph
Re: UT139E and UT139S Digital Multimeters - no discussion?
« Reply #30 on: February 01, 2019, 11:35:57 am »
 Its a 230 VAC
 

Offline Travie21

  • Contributor
  • Posts: 9
  • Country: ph
Re: UT139E and UT139S Digital Multimeters - no discussion?
« Reply #31 on: February 01, 2019, 11:36:44 am »
So theres no way in recovering my meter?
 

Online HKJ

  • Super Contributor
  • ***
  • Posts: 1242
  • Country: dk
    • Tests
Re: UT139E and UT139S Digital Multimeters - no discussion?
« Reply #32 on: February 01, 2019, 11:43:16 am »
So theres no way in recovering my meter?

Remove the protection transistors, if it works then, solder new protection transistor in.
 

Offline Travie21

  • Contributor
  • Posts: 9
  • Country: ph
Re: UT139E and UT139S Digital Multimeters - no discussion?
« Reply #33 on: February 01, 2019, 11:49:00 am »
Btw my meter still works. But the resistance mode is unstable. It blinks from 0000 \$\Omega\$ to OL. DCmV displays OL and a HighVoltage symbol pops. NCV and Capacitance does not also works. But anything else still works fine. Any guess?
 

Offline Fungus

  • Super Contributor
  • ***
  • Posts: 10790
  • Country: 00
Re: UT139E and UT139S Digital Multimeters - no discussion?
« Reply #34 on: February 01, 2019, 01:49:00 pm »
Btw my meter still works. But the resistance mode is unstable. It blinks from 0000 \$\Omega\$ to OL. DCmV displays OL and a HighVoltage symbol pops. NCV and Capacitance does not also works.

Nice definition of "still works".  :-DD

So theres no way in recovering my meter?

Nobody knows for sure, we can't see it from here.

Any guess?

HKJs guess is the most likely but at the end of the day, things break. Learn from it and move on.

 

Offline Hydrawerk

  • Super Contributor
  • ***
  • Posts: 2392
  • Country: 00
Re: UT139E and UT139S Digital Multimeters - no discussion?
« Reply #35 on: February 01, 2019, 10:30:28 pm »
UT139E has some input protection, it should survive 230V, it is not much.
http://en.uni-trend.com.cn/index.php?m=content&c=index&a=show&catid=174&id=185
In the user manual, they say it has a 600V protection on all ranges. http://en.uni-trend.com.cn/uploadfile/2018/1129/20181129032713354.pdf
Amazing machines. https://www.youtube.com/user/denha (It is not me...)
 

Offline Travie21

  • Contributor
  • Posts: 9
  • Country: ph
Re: UT139E and UT139S Digital Multimeters - no discussion?
« Reply #36 on: February 02, 2019, 12:14:17 pm »
So should I check the PTC?
 

Offline Fungus

  • Super Contributor
  • ***
  • Posts: 10790
  • Country: 00
Re: UT139E and UT139S Digital Multimeters - no discussion?
« Reply #37 on: February 02, 2019, 12:59:47 pm »
« Last Edit: February 02, 2019, 01:02:10 pm by Fungus »
 

Offline Travie21

  • Contributor
  • Posts: 9
  • Country: ph
Re: UT139E and UT139S Digital Multimeters - no discussion?
« Reply #38 on: February 02, 2019, 01:13:24 pm »
Should I desolder it first? Or I can test it while its on the circuit? Sorry, I'm just a noob in electronics
 

Offline Travie21

  • Contributor
  • Posts: 9
  • Country: ph
Re: UT139E and UT139S Digital Multimeters - no discussion?
« Reply #39 on: February 02, 2019, 03:09:39 pm »
May I know what kind of PTC are used on 139E?
 

Offline Travie21

  • Contributor
  • Posts: 9
  • Country: ph
 

Offline daedalux

  • Contributor
  • Posts: 31
  • Country: es
Re: UT139E and UT139S Digital Multimeters - no discussion?
« Reply #41 on: April 04, 2019, 10:57:36 pm »
WMZ12A
 

Offline paulbt

  • Contributor
  • Posts: 12
  • Country: ro
Re: UT139E and UT139S Digital Multimeters - no discussion?
« Reply #42 on: June 02, 2020, 02:11:01 pm »
Hello everyone !

I saw people are quite interested about this 139E/S series. I had a thought to buy the S one for a couple of weeks and I finally did it ! I made the purchase from TME last week and today I managed to open it's case and then do some basic tests.

First I want to show you some close-ups from the inside:
"Simplicity is the ultimate sophistication."  Leonardo Da Vinci
 

Offline paulbt

  • Contributor
  • Posts: 12
  • Country: ro
Re: UT139E and UT139S Digital Multimeters - no discussion?
« Reply #43 on: June 02, 2020, 02:41:50 pm »
...then I did some basic comparison measurements against a calibrated Agilent 34410A 6 1/2 digit bench multimeter.

On DCV it reads ~0,1% more than the Agilent. Example: 20,000xx V on Agilent and 20,02 V on UNI-T.

On Ohms scale it reads <1% both less and more than the Agilent, the biggest difference was seen on low value resistors (<60 ohms).

On uA and mA DC scales it reads identical with the Agilent, limited to the number of digits the UNI-T displayed. I tried random values from about 10uA to 500mA (with shorted PS).

On ADC scale it reads ~0,2% less than the Agilent. Here I tried values from tens of mA to about 3A (again with shorted PS).

On mV DC scale it reads almost identical with the Agilent, even if the voltage I was measuring was a bit jumpy (due to noise or PS ripple). You can see the head-to-head comparison in the videos below:




"Simplicity is the ultimate sophistication."  Leonardo Da Vinci
 
The following users thanked this post: Marco1971

Offline paulbt

  • Contributor
  • Posts: 12
  • Country: ro
Re: UT139E and UT139S Digital Multimeters - no discussion?
« Reply #44 on: June 03, 2020, 12:54:05 pm »
Update !

Someone here asked about current consumption and battery life for the UT139S. Here are my results:

- at 3.2V supply (or 2x 1.6V full alkaline batteries) and high brightness display (default setting), it draws 19mA and with low brightness it draws 10mA.

- at 2.4V supply (or 1.2V per battery), the low battery indicator appears and it draws 30mA @ high brightness.

- below 2.22V it will beep, shutdown and continue beeping once every few seconds. Right before this happens, it draws 35mA.

The test was done using my Aim-TTi PL601 power supply and during this whole time I was measuring a random voltage and the reading was rock steady!  :-+

More tests will follow up using a function generator (frequency, duty cycle, max/min recording). If you have any wishes/ideas for testing, please post them here.

    ;)

"Simplicity is the ultimate sophistication."  Leonardo Da Vinci
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf