Author Topic: EEVblog 121GW Multimeter Issues  (Read 82502 times)

yensaw and 1 Guest are viewing this topic.

Online joeqsmith

  • Super Contributor
  • ***
  • Posts: 4833
  • Country: us
Re: EEVblog 121GW Multimeter Issues
« Reply #500 on: August 08, 2018, 05:09:00 am »
Plots comparing the various versions of firmware.   Again, this is the same resistor, same location on the bench, same batteries. 

For 1.25, tried the tape eraser test.   I zoomed into the data and turned off everything except version 1.0, 1.22 and 1.25.   

I also added the autorange speed test to the previous video. 

How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 

Online joeqsmith

  • Super Contributor
  • ***
  • Posts: 4833
  • Country: us
Re: EEVblog 121GW Multimeter Issues
« Reply #501 on: August 08, 2018, 06:03:26 am »
Same data zoomed in a little further with thicker lines to show a better contrast between the data sets. 

It's strange that on every release the noise seems to get worse.  I can go back to an old version and it will calm back down so it does not appear to be anything with the test setup.   It appears to be very reproducible but perhaps something else is going on. 
How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 

Online joeqsmith

  • Super Contributor
  • ***
  • Posts: 4833
  • Country: us
Re: EEVblog 121GW Multimeter Issues
« Reply #502 on: August 08, 2018, 07:45:04 am »
Just for transparency sake and to provide you with some data on repeatability after running the sweep using the new 1.25 firmware I reinstalled  TPW_rules's modified version of 1.02.  Picture showing the test setup. Basically meter sitting on the bench with the CADDOCK TK resistor installed.   Nothing fancy.   This time, I did however at 2450 data points swept around the meter with the tape eraser like I did with 1.25.

The plots show the two data sets using the 1.02 firmware.  One from yesterday and the other just now.  The office temperature again is not constant.   The meter appears almost immune to the tape eraser.   

I included the latest firmware in blue for a reference.  I have to conclude that the firmware is worse than ever in regards to the noise level and sensitivity to the tape eraser.   If anyone feels that the test is invalid for some reason or has some suggestion for a better way to test it, let me know.
How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 

Offline DavidDLC

  • Frequent Contributor
  • **
  • Posts: 732
  • Country: us
Re: EEVblog 121GW Multimeter Issues
« Reply #503 on: August 08, 2018, 02:38:38 pm »
Fw 1.25

1.- I also see intermediate values on the Ohm range.

2.- When looking at the mem values, the background measurements still handles the decimal point, very easy to reproduce:
- Record some values
- Set the meter to ohm
- View the recorded data
- Immediately short the probes

You will see the problem.


3.- The temperature measurement still goes crazy for some time while measuring the mains frequency


More coming

David DLC

 

Offline firewalker

  • Super Contributor
  • ***
  • Posts: 2294
  • Country: gr
Re: EEVblog 121GW Multimeter Issues
« Reply #504 on: August 08, 2018, 05:56:36 pm »
The also doesn;t default to the "white mode" when turned off.

Alexander.
Become a realist, stay a dreamer.

 

Online Dr. Frank

  • Super Contributor
  • ***
  • Posts: 1503
  • Country: de
Re: EEVblog 121GW Multimeter Issues
« Reply #505 on: August 08, 2018, 07:52:13 pm »
DavidDLC and joeqsmith,

concerning the noise, are you referring to data logged to SD card?

The reading on the display is now stable, compared to 1-22, and as far I could determine.

Frank
 

Online joeqsmith

  • Super Contributor
  • ***
  • Posts: 4833
  • Country: us
Re: EEVblog 121GW Multimeter Issues
« Reply #506 on: August 09, 2018, 02:23:44 am »
DavidDLC and joeqsmith,

concerning the noise, are you referring to data logged to SD card?

The reading on the display is now stable, compared to 1-22, and as far I could determine.

Frank
In my case, I am always referring to the data collected on the SD card.  I have no desire to watch the LCD for 40 minutes and try to manually pick out any sort of trend.   

Again, keep in mind this is not the same hardware you are testing.  I have damaged the meter three times and have changed some of the hardware in an attempt to make it more robust.  I have also completely realigned the meter.   Maybe there is some other difference.   

I would expect with your setup you should easily replicate anything I show.   If you are seeing something different there must be something we have not accounted for.   

I did make a short video for you.   I start out with the modified 1.02 firmware.  I just let it run for a few minutes.  You can see the drift as the meter warms up.   Again, I assume this is caused by the Hycon chip they chose.    I always found it strange they used that part after Dave's review of the Keysight meter.    Anyway,  I then reprogrammed the latest firmware and let the meter run for 15 minutes or so to stabilize.   I then captured some video while it continued to run for several more minutes.   

One point of interest is that I understood  the kickstart to have roughly 2000 participants and that the vast majority have been delivered.  I assume very few people have firmware 1.0 installed.   Your recent post where you used the 1.9M was really brought my attention to this potential problem.  It does not seem to be common.  So, it's possible that people are just trusting the meter is fine.   Perhaps they really have no need for a higher class meter and bought it for other reasons.    Another possibility is they are not seeing the problem.   If it's the later, then why.   Also,  why would your meter all of a sudden behave different from mine.    Mine seems to reproduce based on the firmware but then again, as many tests as I have ran, we still don't have a lot of data showing how repeatable my results are.  We may just be chasing our tails right now.  It may be a case where we just have to wait for a next generation of the meter (assuming they go ahead with it) and I can have a look at the latest hardware. 

******************
Pulled the video for now.  I have ran a much larger test and put together a video explaining some of the data I have collected and will include this short clip as part of it.   

****  Updated with additional testing and description ****

« Last Edit: August 09, 2018, 07:18:40 am by joeqsmith »
How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 

Online IanB

  • Super Contributor
  • ***
  • Posts: 9042
  • Country: us
Re: EEVblog 121GW Multimeter Issues
« Reply #507 on: August 09, 2018, 04:11:12 am »
One point of interest is that I understood  the kickstart to have roughly 2000 participants and that the vast majority have been delivered.  I assume very few people have firmware 1.0 installed.   Your recent post where you used the 1.9M was really brought my attention to this potential problem.  It does not seem to be common.  So, it's possible that people are just trusting the meter is fine.

I bought the meter out of curiosity, and because it might have some useful features.

I have not had time to give it a comprehensive evaluation, but I have decided for now that I don't trust any of the resistance ranges.

So I for one don't think the meter is "fine". So far, it passes as a curiosity, but not as a working tool. For a working tool I trust my Brymen meters.
I'm not an EE--what am I doing here?
 

Offline darik

  • Contributor
  • Posts: 18
  • Country: ca
Re: EEVblog 121GW Multimeter Issues
« Reply #508 on: August 09, 2018, 04:56:28 am »
One point of interest is that I understood  the kickstart to have roughly 2000 participants and that the vast majority have been delivered.  I assume very few people have firmware 1.0 installed.   Your recent post where you used the 1.9M was really brought my attention to this potential problem.  It does not seem to be common.  So, it's possible that people are just trusting the meter is fine.

I bought the meter out of curiosity, and because it might have some useful features.

I have not had time to give it a comprehensive evaluation, but I have decided for now that I don't trust any of the resistance ranges.

So I for one don't think the meter is "fine". So far, it passes as a curiosity, but not as a working tool. For a working tool I trust my Brymen meters.

I think most people haven't had the time and inclination to do this kind of evaluation, so who knows how common it is.

I got mine for the low burden and as a curiosity. I personally would have been shocked if it didn't have some problems, I'm a software engineer, I know what version 1.0 is like. I just hope the hardware design is sound enough that the roughest edges can be taken off with firmware updates.
 
The following users thanked this post: Sixstring63

Online Dr. Frank

  • Super Contributor
  • ***
  • Posts: 1503
  • Country: de
Re: EEVblog 121GW Multimeter Issues
« Reply #509 on: August 09, 2018, 04:03:06 pm »
In my case, I am always referring to the data collected on the SD card.  I have no desire to watch the LCD for 40 minutes and try to manually pick out any sort of trend.   

OK, and I was referring to the stability on the display, where you need a couple of seconds only to see, that it's now stable to the last digit
The SD card logging, though, contains completely other data, 50 times more noisy, and a different average value, see graph.
That's not usable, analysis from disassembling by tpw_rules explains the whole story.

Again, keep in mind this is not the same hardware you are testing.  I have damaged the meter three times and have changed some of the hardware in an attempt to make it more robust.  I have also completely realigned the meter.   Maybe there is some other difference.   

I would expect with your setup you should easily replicate anything I show.   If you are seeing something different there must be something we have not accounted for.   

Well, I don't think, that this makes a qualitative difference, as I in fact see the same behavior.

I did make a short video for you.   I start out with the modified 1.02 firmware.  I just let it run for a few minutes.  You can see the drift as the meter warms up.   Again, I assume this is caused by the Hycon chip they chose.    I always found it strange they used that part after Dave's review of the Keysight meter.    Anyway,  I then reprogrammed the latest firmware and let the meter run for 15 minutes or so to stabilize.   I then captured some video while it continued to run for several more minutes.   

Thanks a lot! Very instructive, and confirms that for recent firmware 1-25, the logged data is noisy, in contrast to the displayed data.

One point of interest is that I understood  the kickstart to have roughly 2000 participants and that the vast majority have been delivered.  I assume very few people have firmware 1.0 installed.   Your recent post where you used the 1.9M was really brought my attention to this potential problem.  It does not seem to be common.  So, it's possible that people are just trusting the meter is fine.   Perhaps they really have no need for a higher class meter and bought it for other reasons.    Another possibility is they are not seeing the problem.   If it's the later, then why.   

Well, only few people of this Kickstarter project have the means to check the 121GW in depth, and even less might go into detail, and just trust the manufacturer, with Dave as the initiator in the background.

Nevertheless, it's very positive, that several members of  the eevblog community take their time to make a deep analysis of the faults and traps of this eevblog DMM, and especially for me it's a great pleasure to cooperate with you and tpw_rules on this special problem.

Btw.: I signed up for this 121GW, because I wanted to have THE 'Dave-O-Meter', which is simply iconic.
Initially, I did not expect this instrument to be perfect.
So I also expected to have some fun in detecting errors in the instrument, and in the documentation.

Frank
« Last Edit: August 09, 2018, 04:22:52 pm by Dr. Frank »
 

Offline dcac

  • Regular Contributor
  • *
  • Posts: 122
Re: EEVblog 121GW Multimeter Issues
« Reply #510 on: August 09, 2018, 08:40:42 pm »
I've contacted Hycontek about the HY3131 Configuration Application Notes (APD-DMM003) that's mentioned on their site, and they've kindly emailed it to me.

Maybe it has some useful information for 121gw-re project. I noticed it's not yet included in the pdfs folder so I thought I post it here (had to zip it as it was >1MB):




 
The following users thanked this post: Dr. Frank, exe

Offline EEVblog

  • Administrator
  • *****
  • Posts: 26828
  • Country: au
    • EEVblog
Re: EEVblog 121GW Multimeter Issues
« Reply #511 on: August 09, 2018, 09:36:35 pm »
I wondering if it is because it is a STM32 inside and they're having issues with development + testing. The 121GW development video mentions that it originally a PIC with a choice of a MSP430 as well but UEI changed it for a STM32 later on.

Correct. It was changed from a PIC to an STM32 at their request. I chose the final STM part used, but IIRC they said they hadn't done STM dev before that. We don't have visibility on their development environment and how they use it.
 

Online joeqsmith

  • Super Contributor
  • ***
  • Posts: 4833
  • Country: us
Re: EEVblog 121GW Multimeter Issues
« Reply #512 on: August 09, 2018, 09:52:10 pm »
In my case, I am always referring to the data collected on the SD card.  I have no desire to watch the LCD for 40 minutes and try to manually pick out any sort of trend.   

OK, and I was referring to the stability on the display, where you need a couple of seconds only to see, that it's now stable to the last digit
The SD card logging, though, contains completely other data, 50 times more noisy, and a different average value, see graph.
That's not usable, analysis from disassembling by tpw_rules explains the whole story.
...
Thanks a lot! Very instructive, and confirms that for recent firmware 1-25, the logged data is noisy, in contrast to the displayed data.
After three pages of posts, I though the video may help some people follow along.    During the two longer runs with 1.25 where the camera is pointed at the meter's LCD,  you can see a low frequency drift of several counts.  It's low enough that I could blame it on the room temperature but I don't see with the 1.0 or the modified 1.02 firmware.  Those versions appear to stay within a count once things are stable.   The fact we never see the larger deviations that are present in the CSV file, tells us there is more to the story.   

Again, keep in mind this is not the same hardware you are testing.  I have damaged the meter three times and have changed some of the hardware in an attempt to make it more robust.  I have also completely realigned the meter.   Maybe there is some other difference.   

I would expect with your setup you should easily replicate anything I show.   If you are seeing something different there must be something we have not accounted for.   

Well, I don't think, that this makes a qualitative difference, as I in fact see the same behavior.

I am just giving UEI an out,  something to point the finger at besides themselves.  A bit of sarcasm.
How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 

Offline EEVblog

  • Administrator
  • *****
  • Posts: 26828
  • Country: au
    • EEVblog
Re: EEVblog 121GW Multimeter Issues
« Reply #513 on: August 09, 2018, 10:01:45 pm »
I noticed I have cracked the SD card connector.  I am surprised none of the pins nave broke yet as many times as I have cycled the card in and out.   I always saw this as a mechanically weak point and thought they would do something to try and make it more robust in the final design but it appears to still be the same. 

The SD card was added after the case tooling was done. We did not want to scrap it all and do it again.
The meter was never designed to be a heavy use and convenient data logger (the SD card was always going to be under the cover for safety compliance reasons).
 

Online joeqsmith

  • Super Contributor
  • ***
  • Posts: 4833
  • Country: us
Re: EEVblog 121GW Multimeter Issues
« Reply #514 on: August 09, 2018, 10:21:18 pm »
I personally would have been shocked if it didn't have some problems, I'm a software engineer, I know what version 1.0 is like.

I've seen similar posts.  What's a bit odd in this case is 1.0 is actually lower noise than anything that came after it from the little testing I have ran.  Maybe it's the old hardware.  Maybe they handed the code framework over to a less experienced group.  Hard to say.  Not sure it matters but a year of code development seems to show a backwards trend in this one case.     
How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 

Offline firewalker

  • Super Contributor
  • ***
  • Posts: 2294
  • Country: gr
Re: EEVblog 121GW Multimeter Issues
« Reply #515 on: August 09, 2018, 11:26:04 pm »
Maybe the newer firmware enables more hardware options and it causes the noise.

What is the name of the software you are using to plot the logs?

Alexander.
« Last Edit: August 09, 2018, 11:27:37 pm by firewalker »
Become a realist, stay a dreamer.

 

Online joeqsmith

  • Super Contributor
  • ***
  • Posts: 4833
  • Country: us
Re: EEVblog 121GW Multimeter Issues
« Reply #516 on: August 10, 2018, 12:25:08 am »
I use Labview for all of my Windows software.  You could plot the data with Excel or any other spreadsheet you happen to use. 
How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 
The following users thanked this post: firewalker

Offline floobydust

  • Super Contributor
  • ***
  • Posts: 1660
  • Country: ca
Re: EEVblog 121GW Multimeter Issues
« Reply #517 on: August 10, 2018, 05:27:20 am »
On another product, I have seen the ohms constant-current source be noisy or even oscillate.
Try adding small capacitance across the resistor-under-test to see if it's a hardware issue. Firmware can average small oscillations and AC hum to a point.
 

Offline AdamHi

  • Contributor
  • Posts: 23
  • Country: us
Re: EEVblog 121GW Multimeter Issues
« Reply #518 on: August 11, 2018, 07:49:14 am »
5 mA DC range FAILS again - can anybody replicate?

So i got a replacement 121GW after the problem i had with my first unit (see my posts
 https://www.eevblog.com/forum/testgear/eevblog-121gw-multimeter-issues/msg1692650/#msg1692650
and
https://www.eevblog.com/forum/testgear/eevblog-121gw-multimeter-issues/msg1693298/#msg1693298)

I repeated the same tests with a 1 mA DC source, and got essentially the same results, here are photos showing the poor measurement on the 5 mA DC range, but the perfect measurement on the 50 mA range, on my Amprobe AM270 meter, and also using the uCurrent Gold.

Summary: On the 5mA DC current range, the 121GW reads off, and is quite significantly affected by touching the leads. None of these effects are seen on the 50mA range, on the Amprobe meter, nor when using the uCurrent.

Can anybody replicate these findings? Figure out a way to mitigate this problem? Should I consider the 5mA DC current range to be an "extreme" measurement and i'm just expecting too much? I wouldn't think so in a meter in this price range, considering the Amprobe is a significantly lower price class instrument. I kind of think Dave would be giving a Thumbs Down  :-- on this performance if he was reviewing it.

Thanks.

--adam
 

Online joeqsmith

  • Super Contributor
  • ***
  • Posts: 4833
  • Country: us
Re: EEVblog 121GW Multimeter Issues
« Reply #519 on: August 11, 2018, 08:38:06 am »
I assume you checked your test setup before concluding the 121GW was defecting and returning it.   What's the output of your test signal look like?  How did you check it?   

Again, just to be clear, the meter I have is not  current.  It's a pre-production unit that has been damaged, repaired, modified and recently I completely realigned it with this last round of testing.  I would not expect my results to be the same as yours.   

So for what it's worth, I currently have firmware version 1.25 installed.   I attempted the same setup with a known clean 1mADC source.  I am able to put my hand around the leads with little effect.  The meter stays within five counts.  Using it like I normally would, not touching anything, the meter stays within a count short term.    Picture showing my Brymen and the 121 in series.  1mADC source.  5mA range.   

How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 
The following users thanked this post: Marco1971

Offline dcac

  • Regular Contributor
  • *
  • Posts: 122
Re: EEVblog 121GW Multimeter Issues
« Reply #520 on: August 11, 2018, 10:44:48 am »
If I compare my U1252A and 121gw - measuring about 1mA in series with each other and using uA range on U1252A to get the same resolution - I can make 121gw go +/- 30 counts depending on where I touch the cables. The U1252A only flicker on 1 count.

FW ver. 1.25

 

Offline AdamHi

  • Contributor
  • Posts: 23
  • Country: us
Re: EEVblog 121GW Multimeter Issues
« Reply #521 on: August 11, 2018, 01:07:45 pm »
Thanks for checking in Joe.
I assume you checked your test setup before concluding the 121GW was defecting and returning it.   

I was asked to perform the two DMM's in series set-up as shown in second post, and again here, before the meter defected back to KaneUSA. I showed that 121GW was way off and bounced around, while other meter, connected in series, was rock solid. 121GW was also rock solid on the next range up (50mA). And in this most recent post showed that uCurrent also gives rock solid output given the same 1mA source.

BTW - New meter is running FW 1.25

Quote
What's the output of your test signal look like?  How did you check it?

Connected the same 1mA source to uCurrent (1mV/uA), and put the voltage output of that to scope. Wasn't sure of exact proper method, was a bit kludgy looking (10x scope probe clipped to one output, ground to other), DC coupled; see other parameters in screen grabs below at 50us, 5ms, and 100ms per division.

With the sensitivity to touching the probes that i have seen on both 121GW's, but not on my Amprobe or uCurrent, as has
. . . . I can make 121gw go +/- 30 counts depending on where I touch the cables. The U1252A only flicker on 1 count.
it seems that the 121GW is excessively sensitive to either stray capacitance, or EM pickup, pushing it out of spec.
 

Offline EEVblog

  • Administrator
  • *****
  • Posts: 26828
  • Country: au
    • EEVblog
Re: EEVblog 121GW Multimeter Issues
« Reply #522 on: August 11, 2018, 05:36:47 pm »
5 mA DC range FAILS again - can anybody replicate?

So i got a replacement 121GW after the problem i had with my first unit (see my posts
 https://www.eevblog.com/forum/testgear/eevblog-121gw-multimeter-issues/msg1692650/#msg1692650
and
https://www.eevblog.com/forum/testgear/eevblog-121gw-multimeter-issues/msg1693298/#msg1693298)

I repeated the same tests with a 1 mA DC source, and got essentially the same results, here are photos showing the poor measurement on the 5 mA DC range, but the perfect measurement on the 50 mA range, on my Amprobe AM270 meter, and also using the uCurrent Gold.

Summary: On the 5mA DC current range, the 121GW reads off, and is quite significantly affected by touching the leads. None of these effects are seen on the 50mA range, on the Amprobe meter, nor when using the uCurrent.

Can anybody replicate these findings? Figure out a way to mitigate this problem? Should I consider the 5mA DC current range to be an "extreme" measurement and i'm just expecting too much? I wouldn't think so in a meter in this price range, considering the Amprobe is a significantly lower price class instrument. I kind of think Dave would be giving a Thumbs Down  :-- on this performance if he was reviewing it.

Thanks.

--adam

I have never seen this issue. Many people have measured all current range and they are spot on. Every unit is fully calibrated before shipping. You must be using it in some environment or under some condition that is causing some sort of interference issue. We will need to be able to replicate this before being able to comment further.
« Last Edit: August 11, 2018, 05:38:22 pm by EEVblog »
 

Offline EEVblog

  • Administrator
  • *****
  • Posts: 26828
  • Country: au
    • EEVblog
Re: EEVblog 121GW Multimeter Issues
« Reply #523 on: August 11, 2018, 05:59:24 pm »
v1.26 is now on the website for download. We have not tried it yet, but UEi have said that it now logs the displayed data instead of the bargraph data. There should now be no noise on the logged data as per previous versions. Please try it and report.
 
The following users thanked this post: Digital Corpus, 1anX, Marco1971

Offline firewalker

  • Super Contributor
  • ***
  • Posts: 2294
  • Country: gr
Re: EEVblog 121GW Multimeter Issues
« Reply #524 on: August 11, 2018, 06:31:57 pm »
This is the only change?

Alexander.
Become a realist, stay a dreamer.

 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf