Author Topic: EEVblog 121GW Multimeter Issues  (Read 30874 times)

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Offline bryanp

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EEVblog 121GW Multimeter Issues
« on: January 08, 2018, 11:21:24 am »
Hi Dave (and everyone else),

I have done a search on the forums for a dedicated 1212GW support thread but could not find one, apologies if I have missed it.

I just received my 121GW and it is awesome. I was looking over the set up menu to set the date and time etc but am having a few issues.

1. If I change the year (it defaults to 2016), the day, month, hour or minutes the setting does not stick/save. Changing (and having them save) other set up menu items works fine. I have tried cycling the power on the meter after making a change but that has no effect.

2. Is it possible to disable the beep please, at least for button presses and any time the rotary switch is changed? The beep is loud which is great for continuity etc but after trying to figure out how to change the date/time it is starting to annoy.

3. There appears to be a set up menu option between item 7 (Hour-Minute) and item 8 Logging Interval. This set up menu item is not mentioned in the manual, and it is present on at least the Low Z, V and Ohms ranges. The set up menu item consists of 5 digits, it seems to default to 5 zeros but these numbers can be changed from 0-9 and once you hold down the setup button to edit this option you can use the set up button to switch between each digit. I do not know what these numbers/digits mean. I changed the last digit (on the right hand side) to a value and saved it but this seemed to have no effect.

4. An erratum for the manual in regards to changing the Hour-Minute and Month-Day set up menu items should include some mention of a long setup button press to switch between month and day for instance and a short setup button press to save and move on. This functionality seems to be the opposite to the five zeros set up menu item (mentioned above) as a short press switches between zeros/digits and a long press saves and switches to the next set up menu item.

Please let me know if I am being an idiot and have missed something obvious.

Thanks and the meter really is a beast.
 

Online EEVblog

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EEVblog 121GW Multimeter Issues
« Reply #1 on: January 09, 2018, 07:59:09 am »
This is a thread for discussion of bugs and issues found with the 121GW meter.
Please state your version number.
 

Offline exe

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Re: EEVblog 121GW Multimeter Issues
« Reply #2 on: January 09, 2018, 08:54:50 am »
Hi Dave!

On my "U-1.01" low z doesn't work until voltage reaches 11V. Then it works fine (but shows only one digit after dot (like 11.3V), intentionally low resolution?).

Update rate is like 0.5samples/s. Tried to change "In x" (by default it's ln 0), no luck.
 

Offline amspire

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Re: EEVblog 121GW Multimeter Issues
« Reply #3 on: January 09, 2018, 11:03:29 am »
1. If I change the year (it defaults to 2016), the day, month, hour or minutes the setting does not stick/save. Changing (and having them save) other set up menu items works fine. I have tried cycling the power on the meter after making a change but that has no effect.
Just got my meter today, and I am very impressed. Calibration is pretty much spot on.

The time/date works fine on my meter (version U-1.01). It arrived with the correct time and it seems to keep correct time even after changing the batteries. 

After changing a time/date field, are you pressing the setup button for about two seconds until the beep to save the change?
« Last Edit: January 09, 2018, 11:14:14 am by amspire »
 
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Offline DrGeoff

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Re: EEVblog 121GW Multimeter Issues
« Reply #4 on: January 09, 2018, 11:12:53 am »
1. If I change the year (it defaults to 2016), the day, month, hour or minutes the setting does not stick/save. Changing (and having them save) other set up menu items works fine. I have tried cycling the power on the meter after making a change but that has no effect.

Confirmed. I have 2072-06-12 as the default date and changing it does not save.
Time does not save correctly either.

2. Is it possible to disable the beep please, at least for button presses and any time the rotary switch is changed? The beep is loud which is great for continuity etc but after trying to figure out how to change the date/time it is starting to annoy.

Yes please!
Was it really supposed to do that?
 

Offline bryanp

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Re: EEVblog 121GW Multimeter Issues
« Reply #5 on: January 09, 2018, 11:15:14 am »
Thanks amspire for the help, I tried the long setup button press and the date and time etc changes were saved. Could have sworn I tried that yesterday but thanks.

My version number BTW is also U-1.01

Still not sure what the five digits thing is in the set up menu between the Hour-Minute and Logging Interval is. Does anyone else have this extra set up menu item?

 

Offline DrGeoff

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Re: EEVblog 121GW Multimeter Issues
« Reply #6 on: January 09, 2018, 11:19:17 am »
After changing a time/date field, are you pressing the setup button for about two seconds until the beep to save the change?

I missed that, not in the manual, just 'press setup'. Date/time appears set OK now that I hold setup down for an extended time.

Thanks!
Was it really supposed to do that?
 

Offline amspire

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Re: EEVblog 121GW Multimeter Issues
« Reply #7 on: January 09, 2018, 11:23:12 am »
1. If I change the year (it defaults to 2016), the day, month, hour or minutes the setting does not stick/save. Changing (and having them save) other set up menu items works fine. I have tried cycling the power on the meter after making a change but that has no effect.

Confirmed. I have 2072-06-12 as the default date and changing it does not save.
Time does not save correctly either.
Are you saying that if you change the year to 2018 and hold the setup button down till the beep, then if you check the year again, it is back to 2072?
 

Offline DrGeoff

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Re: EEVblog 121GW Multimeter Issues
« Reply #8 on: January 09, 2018, 11:28:48 am »
1. If I change the year (it defaults to 2016), the day, month, hour or minutes the setting does not stick/save. Changing (and having them save) other set up menu items works fine. I have tried cycling the power on the meter after making a change but that has no effect.

Confirmed. I have 2072-06-12 as the default date and changing it does not save.
Time does not save correctly either.
Are you saying that if you change the year to 2018 and hold the setup button down till the beep, then if you check the year again, it is back to 2072?
Yes, I cycled through all the date/times and set them. Then cycling back to the year again it was unchanged. There must be a difference between pressing the Setup button to cycle to the next setup option and holding it for longer to save the current value. The manual was not clear on this.

Quote
To change the date items:
1. Navigate to the menu item.
2. Hold SETUP
3. Press UP and DOWN to configure the date/time item.
4. Press SETUP again to save
Was it really supposed to do that?
 

Offline amspire

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Re: EEVblog 121GW Multimeter Issues
« Reply #9 on: January 09, 2018, 11:32:03 am »
Yes, I cycled through all the date/times and set them. Then cycling back to the year again it was unchanged. There must be a difference between pressing the Setup button to cycle to the next setup option and holding it for longer to save the current value. The manual was not clear on this.

Quote
To change the date items:
1. Navigate to the menu item.
2. Hold SETUP
3. Press UP and DOWN to configure the date/time item.
4. Press SETUP again to save
You have to hold the setup button for 2 seconds until the beep to change the date/time settings. Otherwise it is not changed. I don't think it does clearly say that in the manual.
 
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Offline DrGeoff

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Re: EEVblog 121GW Multimeter Issues
« Reply #10 on: January 09, 2018, 11:40:16 am »
Also, as an aside, if you hit 'Setup' in the AC volts display you get dBm in the smaller top display.
Very useful.
Was it really supposed to do that?
 

Offline amspire

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Re: EEVblog 121GW Multimeter Issues
« Reply #11 on: January 09, 2018, 10:26:02 pm »
Looks like full scale of the 121GW is 54999 and not 49999 - which is fantastic.  :clap: The specifications in the manual probably should be updated to mention this.
 

Offline exe

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Re: EEVblog 121GW Multimeter Issues
« Reply #12 on: January 09, 2018, 10:45:14 pm »
BTW, is there a source code so I could try fix some problems by myself? (sorry if this was asked before)
 

Offline amspire

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Re: EEVblog 121GW Multimeter Issues
« Reply #13 on: January 09, 2018, 11:00:44 pm »
The source code for the Bluetooth 121GW App is available. The code for the Multimeter will likely never be open source according to Dave.
 

Offline mikeselectricstuff

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Re: EEVblog 121GW Multimeter Issues
« Reply #14 on: January 09, 2018, 11:06:36 pm »
The source code for the Bluetooth 121GW App is available. The code for the Multimeter will likely never be open source according to Dave.
But I suspect someone will disassemble it at some point...
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Offline Fungus

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Re: EEVblog 121GW Multimeter Issues
« Reply #15 on: January 10, 2018, 12:09:16 am »
The source code for the Bluetooth 121GW App is available. The code for the Multimeter will likely never be open source according to Dave.
But I suspect someone will disassemble it at some point...

IIRC the point of not open-sourcing it is that messing with the firmware could affect the safety of the meter so there's no way they can officially sanction that or help people to do it.

If you want to mess around with it, that's your problem, not theirs.

(And I hope you make people aware of this problem if you start uploading modified firmware somewhere)

Edit: The best course of action if you want something "fixed" is to ask here. Dave could maybe pass sensible requests along to the manufacturer...
« Last Edit: January 10, 2018, 12:12:33 am by Fungus »
 

Offline exe

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Re: EEVblog 121GW Multimeter Issues
« Reply #16 on: January 10, 2018, 04:55:29 am »
IIRC the point of not open-sourcing it is that messing with the firmware could affect the safety of the meter so there's no way they can officially sanction that or help people to do it.

Is it a law or requirement? Or they try to be on a "safe" side?
 

Offline exe

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Re: EEVblog 121GW Multimeter Issues
« Reply #17 on: January 10, 2018, 04:59:23 am »
Opened the manual, it says "This meter is hackable, go for it.". Challenge accepted  :box:
 

Offline mikeselectricstuff

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Re: EEVblog 121GW Multimeter Issues
« Reply #18 on: January 10, 2018, 07:45:50 am »
The source code for the Bluetooth 121GW App is available. The code for the Multimeter will likely never be open source according to Dave.
But I suspect someone will disassemble it at some point...

IIRC the point of not open-sourcing it is that messing with the firmware could affect the safety of the meter so there's no way they can officially sanction that or help people to do it.

Do the IEC test equipment standards actually cover software funcitionality ( e.g. not under-reading)?
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Online bicycleguy

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Re: EEVblog 121GW Multimeter Issues
« Reply #19 on: January 10, 2018, 09:49:41 am »
FYI
Possible bugs in User's Manual (Rev 11 December 2017):
1.  No mention of input impedance for any V inputs.
2.  No mention of Low Z position on dial.

 

Offline beanflying

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Re: EEVblog 121GW Multimeter Issues
« Reply #20 on: January 10, 2018, 11:30:36 am »
Slow Auto Ranging.

Manually set Range response time is great. So if you are testing a batch best to lock it in.

Without knowing how the code is written but checking out the bottom of the display shows it start at MOhms then cycle down through the ranges until it get into limits, it then seems to run a stepped routine to decide where to place the decimal point before displaying a value? Remove display indicators and anything not absolutely necessary to make the auto range work well and safely to improve the speed. So some firmware code optimization needed if possible?
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Offline lowimpedance

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Re: EEVblog 121GW Multimeter Issues
« Reply #21 on: January 10, 2018, 02:55:51 pm »
Minor update for the next manual revision; The main photo needs updating to show the 500mA text over the 'A' terminal and the Bluetooth symbol is missing between the 'SETUP' an '1mS PEAK' buttons.
Manual I am looking at was last revised 11th Dec.
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I'll show you current !
 the odd multimeter or 2 or 3 or 4...or........never mind
 

Offline VK5RC

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Re: EEVblog 121GW Multimeter Issues
« Reply #22 on: January 10, 2018, 07:23:10 pm »
+1 re the relative slowness of auto-ranging, otherwise very happy :-+
Whoah! Watch where that landed we might need it later.
 
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Offline beanflying

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Re: EEVblog 121GW Multimeter Issues
« Reply #23 on: January 10, 2018, 07:42:42 pm »
Yes, I cycled through all the date/times and set them. Then cycling back to the year again it was unchanged. There must be a difference between pressing the Setup button to cycle to the next setup option and holding it for longer to save the current value. The manual was not clear on this.

Quote
To change the date items:
1. Navigate to the menu item.
2. Hold SETUP
3. Press UP and DOWN to configure the date/time item.
4. Press SETUP again to save
You have to hold the setup button for 2 seconds until the beep to change the date/time settings. Otherwise it is not changed. I don't think it does clearly say that in the manual.

Just playing with the settings on mine and yep. Manual needs to use the words "Long Press" or similar to save and to jump from the hours set to minutes.

Minor on the manual but the Index and Pages are out of step as no doubt more content has been added and will be :)
« Last Edit: January 10, 2018, 07:46:07 pm by beanflying »
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Offline blueskull

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Re: EEVblog 121GW Multimeter Issues
« Reply #24 on: January 10, 2018, 07:53:31 pm »
IIRC the point of not open-sourcing it is that messing with the firmware could affect the safety of the meter so there's no way they can officially sanction that or help people to do it.

Dave maybe can sell a version with open source firmware as DMM development kit? As a dev kit, you can basically bypass any certification requirements.
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Offline exe

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Re: EEVblog 121GW Multimeter Issues
« Reply #25 on: January 10, 2018, 08:00:44 pm »
BTW, I found the problem of slow updates. My meter came with "AC+DC" mode activated. In this mode it is very slow :(. And yeah, beeping sucks.
 

Offline BBBbbb

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Re: EEVblog 121GW Multimeter Issues
« Reply #26 on: January 10, 2018, 08:00:51 pm »
IIRC the point of not open-sourcing it is that messing with the firmware could affect the safety of the meter so there's no way they can officially sanction that or help people to do it.

Dave maybe can sell a version with open source firmware as DMM development kit? As a dev kit, you can basically bypass any certification requirements.
I do believe that it's not his to do this, it's up to UEi, as they hold the IP. Dave gave up a lot of his rights regarding the meter as a part of the deal between them, from what I understood. 
 

Offline idpromnut

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Re: EEVblog 121GW Multimeter Issues
« Reply #27 on: January 10, 2018, 11:53:01 pm »
Dave has said that the issue with open sourcing the firmware is that it is UEi's source code, but they don't own all the rights to the code (i.e. they don't have the right to re-distribute the source code in its entirety). Getting this sorted out seems like it will be more trouble than it is worth for UEi, so they are unlikely to do it.

I think Dave mentioned that UEi /might/ be willing to opensource certain bits of the firmware (the LCD driver for instance); he would need to confirm that however.

If you are going to go hacking around, remember a couple of things:

- The STM32 line of mcus offer "read out protection", so directly reverse engineering the firmware from the meter might be tricky (but the protection has been weakened, see paper referencing this https://www.aisec.fraunhofer.de/en/FirmwareProtection.html),
- Even if a firmware update blob is released (say a v1.02), it will likely not include at least one of the boot loaders, and may not include any bootloader. That means using the existing bootloader as-is might be tricky (i.e. reverse engineering the application might be possible by looking at the firmware update blob),
- There is a JTAG header on the board IIRC, but you can't use it when read-out proctection is enabled (if I'm remembering correctly). But that means re-writing a new firmware from scratch is totally possible (and I am pretty sure this is what the "Hack away!" sentence in the manual refers to).
« Last Edit: January 10, 2018, 11:54:54 pm by idpromnut »
 

Offline mikeselectricstuff

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Re: EEVblog 121GW Multimeter Issues
« Reply #28 on: January 11, 2018, 02:50:59 am »
From a video in another thread, it seems it takes 7 seconds to autorange from open to zero ohms - how can Dave have considered this remotely acceptable ?
Any more than 1 second is too slow.
The bargraph seems to respond quickly, so why isn't it using that conversion for ranging?
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Online dr.diesel

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Re: EEVblog 121GW Multimeter Issues
« Reply #29 on: January 11, 2018, 03:23:14 am »
From a video in another thread, it seems it takes 7 seconds to autorange from open to zero ohms - how can Dave have considered this remotely acceptable ?

He couldn't have, hopefully a last minute change that can be easily fixed, the delay is agonizing. 

Joe might be able to comment on how the pre-production 121 behaved?

Online gnavigator1007

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Re: EEVblog 121GW Multimeter Issues
« Reply #30 on: January 11, 2018, 03:46:07 am »
That autoranging is really atrocious lol. Just raced it against every handheld meter I had nearby (BM235, U1252A, U1273A, UT61E, & a UT210E just for kicks). UT210E was the next slowest, but still seems like a rocket next to the 121GW. Others were all reasonably close with the the BM235 & UT61E appearing slightly faster than the Agilent/Keysights. One of the reasons I was eager to get an early 121GW was for the fun of finding issues like this. Not sure how this slipped past Dave & UEI, but hopefully it's a fairly simple fix.
 

Offline exe

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Re: EEVblog 121GW Multimeter Issues
« Reply #31 on: January 11, 2018, 05:49:00 am »
Okay, we'll not see FW released for opensource, I got it. But I want to roll my own. Please post information how to do this or a minimal buildable example. Like, a zip-archive with a Makefile inside.

UEi's source code, but they don't own all the rights to the code (i.e. they don't have the right to re-distribute the source code in its entirety).

Alright, let them ship without that pieces. I can try to write open-source equivalent of that pieces.
 

Offline markb82

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Re: EEVblog 121GW Multimeter Issues
« Reply #32 on: January 11, 2018, 06:25:23 am »
Anyone else have a lot of play (loosy-goosy) in their rotary switch?

Also my meter flashes the backlight when first turning on (firmware issue?) and beeps every time you switch settings (ie rotate the rotary switch) which is very annoying.
 

Online gnavigator1007

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Re: EEVblog 121GW Multimeter Issues
« Reply #33 on: January 11, 2018, 06:46:04 am »
Anyone else have a lot of play (loosy-goosy) in their rotary switch?

Also my meter flashes the backlight when first turning on (firmware issue?) and beeps every time you switch settings (ie rotate the rotary switch) which is very annoying.

I actually like the feel of the switch quite a bit. Definitely easier to turn on one handed than others. On some of my meters with stiffer switches I'll occasionally use so much force that I turn past the selection I intended. The beeping doesn't bother me, but should definitely have have an option to turn it off. I've been wondering about that backlight flash too. Flashes briefly turning on from either off position. Went back and rewatched one of Dave's videos to make sure others did it. Hard to see in the video, but they did it too.
 

Offline VK5RC

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Re: EEVblog 121GW Multimeter Issues
« Reply #34 on: January 11, 2018, 08:16:38 am »
Switch on mine is good.
Whoah! Watch where that landed we might need it later.
 

Offline DrGeoff

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Re: EEVblog 121GW Multimeter Issues
« Reply #35 on: January 11, 2018, 09:09:22 am »
I am sure Dave will do a full review of the meter in one of his videos after the holidays.
Was it really supposed to do that?
 

Online EEVblog

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Re: EEVblog 121GW Multimeter Issues
« Reply #36 on: January 11, 2018, 09:15:44 am »
I do believe that it's not his to do this, it's up to UEi, as they hold the IP. Dave gave up a lot of his rights regarding the meter as a part of the deal between them, from what I understood.

Just to be clear, I have ZERO legal rights to this meter apart from exclusive distributorship.
I did not pay a single cent for its development.
 
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Offline joeqsmith

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Re: EEVblog 121GW Multimeter Issues
« Reply #37 on: January 11, 2018, 10:45:55 am »
From a video in another thread, it seems it takes 7 seconds to autorange from open to zero ohms - how can Dave have considered this remotely acceptable ?

He couldn't have, hopefully a last minute change that can be easily fixed, the delay is agonizing. 

Joe might be able to comment on how the pre-production 121 behaved?

I have, please see the following:
http://www.eevblog.com/forum/testgear/new-eevblog-branded-multimeter-coming/375/
How electrically robust is your meter?? http://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 
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Offline markb82

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Re: EEVblog 121GW Multimeter Issues
« Reply #38 on: January 11, 2018, 12:44:50 pm »
Just to be clear, I have ZERO legal rights to this meter apart from exclusive distributorship.
I did not pay a single cent for its development.

How about the open source-ness of the schematics?  It was on the feature list of the Kickstarter.
 

Offline ez24

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Re: EEVblog 121GW Multimeter Issues
« Reply #39 on: January 11, 2018, 01:10:06 pm »
Watching
YouTube and Website Electronic Resources ------>  http://www.eevblog.com/forum/other-blog-specific/a/msg1341166/#msg1341166
 

Offline floobydust

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Re: EEVblog 121GW Multimeter Issues
« Reply #40 on: January 11, 2018, 01:54:21 pm »
For people modifying the firmware, I'd say that invalidates the 61010 agency safety approvals.
A multimeter is expected to function a particular way, i.e. display hazardous voltages correctly after test scenarios and who would re-test those after adding a super-fast autoranging hack?
 

Online EEVblog

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Re: EEVblog 121GW Multimeter Issues
« Reply #41 on: January 11, 2018, 04:11:20 pm »
IIRC the point of not open-sourcing it is that messing with the firmware could affect the safety of the meter so there's no way they can officially sanction that or help people to do it.

Dave maybe can sell a version with open source firmware as DMM development kit? As a dev kit, you can basically bypass any certification requirements.

There is absolutely nothing stopping anyone writing their own firmware and making it open source.
 

Offline amspire

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Re: EEVblog 121GW Multimeter Issues
« Reply #42 on: January 11, 2018, 04:30:36 pm »
mVA Problem: (Confirmed by DrGeoff)

I seem to have a definite measurement problem on the mVA range in DC. Can anyone confirm this on their meters?

If I have a test setup with a power supply and a precision 100ohm resistor and I am putting 5V across the resistor, then as long as the current flowing into the mAuA socket is positive, I get 5.0000V across the resistor, 50.000mA current and 250.00 mVA. All good. Just using absolute numbers here - not worrying about the +/- polarities.

If I swap the power supply polarity - nothing else changes, I get  5.000V, 0.0368mA and 55.215 mVA. The current is wrong and the mVA product makes no sense.

The configuration I used was the mAuA socket to the power supply, the multimeter common to one side the resistor load, the V/Ohms input to the other side of the load that also connects to the other power supply output. I am using this configuration so that the multimeter is measuring the actual voltage across the load. The problem happens whether or not the v/Ohms input is connected or not, so my meter just cannot measure negative currents over exactly 10mA in the mVA/VA mode.

The problem occurs exactly when the current reaches 10.000mA. It works perfectly at 9.999mA with both power supply polarities. At 10.000mA, it fails. This makes it look like a software bug.

The mAuA input works fine in A/mA switch setting. This is only a problem in the mVA/VA mode.

The same problem does not occur using the A input for current instead of the mAuA input - at least at up to 100mA.  The problem might be there using the A input at higher currents, but I cannot test that right now.

I have not tested this in AC mode, but assuming the RMS converter is only supplying positive voltages to the measurement chip, I would guess that AC mVA mode probably is fine.

UPDATE:

The same problem happens with the A input when measuring VA. If the current into the A socket reaches -1.0000A it wraps around to zero. -0.9999A is fine. Same thing happens with the mAuA socket at -10mA. Both inputs work perfectly in the mVA/VA modes with positive input currents.

The problem seems to be connected to Autoranging with negative currents - if you use the range button, you can get the right numbers with negative currents. So it seems that the current measurement autoranging for mVA/VA measurements does not work properly for negative currents. It works properly for positive input currents. If the firmware can be fixed to get the measurement chip in the correct range for the applied negative DC current, this problem should be fixed.

It would seem that with negative currents, the mVA get stuck in the 5.4999mA range. It actually seem to keep measuring up to 9.9999mA  - that is 80% overrange before rolling over to 0.00000 at 10mA. It then continues to measure correctly to 11mA (with the lost first digit) which is 100% overrange!. After that, I think the poor current input has had enough. At some point, the current input totally overloads and just produces rubbish numbers. The multimeter does not change to the 54.999mA range with mVA negative currents or to the 5.4999A or 10A ranges for VA negative currents at all if Autoranging is enabled.
« Last Edit: January 11, 2018, 08:10:37 pm by amspire »
 
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Offline DrGeoff

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Re: EEVblog 121GW Multimeter Issues
« Reply #43 on: January 11, 2018, 04:52:05 pm »
mVA Problem:

I seem to have a definite measurement problem on the mVA range in DC. Can anyone confirm this on their meters?

If I have a test setup with a power supply and a precision 100ohm resistor and I am putting 5V across the resistor, then as long as the current flowing into the mAuA socket is positive, I get 5.0000V across the resistor, 50.000mA current and 250.00 mVA. All good. Just using absolute numbers here - not worrying about the +/- polarities.

If I swap the power supply polarity - nothing else changes, I get  5.000V, 0.0368mA and 55.215 mVA. The current is wrong and the mVA product makes no sense.

The configuration I used was the mAuA socket to the power supply, the multimeter common to one side the resistor load, the V/Ohms input to the other side of the load that also connects to the other power supply output. I am using this configuration so that the multimeter is measuring the actual voltage across the load. The problem happens whether or not the v/Ohms input is connected or not, so my meter just cannot measure negative currents over exactly 10mA in the mVA/VA mode.

The problem occurs exactly when the current reaches 10.000mA. It works perfectly at 9.999mA with both power supply polarities. At 10.000mA, it fails. This makes it look like a software bug.

The mAuA input works fine in A/mA switch setting. This is only a problem in the mVA/VA mode.

The same problem does not occur using the A input for current instead of the mAuA input - at least at up to 100mA.  The problem might be there using the A input at higher currents, but I cannot test that right now.

Can confirm this.
I repeated the experiment using a bipolar supply, leaving the 0V cable intact and switching from the +ve supply terminal to the -ve supply terminal. Same results as you see.
Was it really supposed to do that?
 
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Offline amspire

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Re: EEVblog 121GW Multimeter Issues
« Reply #44 on: January 11, 2018, 08:14:56 pm »
I discovered more details of the DC mVA/VA problem and added it to post (2 posts back). It is an Autoranging bug.

No wonder people want to hack this multimeter - the measurement chip keeps working to the 99999 count and actually keeps working till the 109999 count with the slight problem that the first "1" digit is lost - the 5 digit counter just wraps around. The overload display at 55000 is just a firmware thing.

Until this bug is fixed, you can actually get the meter to read currents to 9.9999mA and 0.99999A right now.
« Last Edit: January 11, 2018, 08:37:17 pm by amspire »
 

Online nidlaX

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Re: EEVblog 121GW Multimeter Issues
« Reply #45 on: January 11, 2018, 08:54:58 pm »
One person on Kickstarter reported a poorly soldered connection to the LCD backlight.
 

Offline mikeselectricstuff

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Re: EEVblog 121GW Multimeter Issues
« Reply #46 on: January 11, 2018, 09:05:20 pm »
IIRC the point of not open-sourcing it is that messing with the firmware could affect the safety of the meter so there's no way they can officially sanction that or help people to do it.

Dave maybe can sell a version with open source firmware as DMM development kit? As a dev kit, you can basically bypass any certification requirements.

There is absolutely nothing stopping anyone writing their own firmware and making it open source.
Are the formats of the calibration data, and the firmware update file public yet ?
Those would be prerequisites for a proper OS alternative FW implementation.
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Offline flano

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Re: EEVblog 121GW Multimeter Issues
« Reply #47 on: January 11, 2018, 09:42:19 pm »
Found something interesting on the low Z range with a 100khz squarewave, 5Vpp and 5V offset.

I get a reading of 158V?

Edit. Firmware is 1.01

Mike.
« Last Edit: January 12, 2018, 08:20:59 am by flano »
 
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Offline chriz2600

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Re: EEVblog 121GW Multimeter Issues
« Reply #48 on: January 12, 2018, 02:50:12 am »
Hi Dave,

I received my unit today, and had some problems with continuity test.
From time to time there seems to be a contact problem related to the rotary switch, which occurs when switching from off to continuity mode. I made a short video showing this problem:
- inputs are shortened.
- version is 1.02

 
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Offline Iagash

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Re: EEVblog 121GW Multimeter Issues
« Reply #49 on: January 12, 2018, 04:15:52 am »
Hi Dave,

I also got my meter today. Thanks for your effort. I like the probes and the build quality. I have no equipment to test its precision.

Firmware version is: U-1.02

Here are the things I don't like or consider a fault:

  • The range switch is unreliable, you sometimes need to poke it a bit until the meter behaves properly.
  • The inability to disable the excessive beeping or at least lowering the volume get's annoying fast.
  • Autoranging speed in Ohms is way too slow.
  • Autoranging in the other modes isn't fast either.
  • Burden voltage display get's disabled each time the range is switched (eg. mA to uA).
  • Burden voltage display slows down the update rate to a crawl (around one update every 2s).
  • VA update rate is also very slow. It seems whenever two values are measured the update speed is reduced by a factor of 10.
  • When two values are measured, the bar graph "blinks" sometimes. It seems to display the other value for one LCD update frame every now and then. This is annoying if you watch the meter out the corner of your eye.
  • In lowZ mode the meter only starts to display a value >0 when the voltage rises to around 11.5V. When the voltage is lowered from 12V it works down to around 3V. If this is expected behaviour, it should be documented in the manual.
  • Bluetooth logging via the app in VA mode is simply broken. The log is from a 12V 10W light bulb on a linear power supply modulated between 6W and 10W  by manually turning the knob. The display on the meter is correct, the bluetooth data isn't. There is no way for the bulb to use over 100W without blowing up. (see below)
  • Update rate via bluetooth is too low and uneven to be useful. Have a look at the time stamps. (see below)
  • There is spurious data corruption in bluetooth packets.
  • Creation time of the logfile in the file system is wrong. (See below, the forum seems unable to mix lists and quotes.)
  • SD-card logging lacks proper time stamps. There is only one written at the beginning of the file. After that there  is no more time information, making the feature useless, since no proper graph can be generated as the delay between the lines is not known when you select the fastest logging mode. When selecting a defined delay, there is no way to tell if the log is accurate or if lines are dropped.
  • VA mode is limited to max. 55V (fix it or document it).
  • It would be nice if bluetooth VA mode in the App would log at least two values VA + V or VA + A, or V + A, to be able to compute the other value.
  • Using a binary coding in bluetooth logging instead of ASCII coding could at least double the update rate.
  • The meter crashes immediately if you enable SD-card logging with no SD-card inserted
  • When logging to SD-card autoranging stops working even tough it is indicated as active in the display. After stopping logging you have to long press the RANGE button to reenable it.
  • When logging a long time to the SD-card the "k" indicator after the record counter is flickering, this indicates issues in the display update routine.
  • When logging to SD-card the secondary display is fixed to the log-counter and there is no way to display Hz or A/V in modes where the secondary display is used.

I would be most glad if the logging features could be improved. Please add at least sub-second precision time stamps to the SD-card logfile. I don't care if they are absolute or relative value to the start of the logging but just a counter is not enough. This is the point I care about, since I have no other meter with this capability.

All other points would be nice to have but are not important to me.

A higher bluetooth speed would be second, but I have a meter with a real serial Adapter, so I could live without it. At least a deterministic logging interval would be a win for bluetooth.

Anyway, thanks for the meter, it's fun to play around with.

Quote
mm@ovid:~/121gw$ ls -l
total 232
-rwxr-xr-x   1 mm mm  39189 Feb  9  2006 18011100.CSV
-rwxr-xr-x   1 mm mm 117848 Dez 29 07:17 EEVBlog.bin
drwxr-xr-x   2 mm mm   4096 Dez  4 08:31 System Volume Information

Quote
time (s), Power DC (VA)
0.66214, 10.04
2.319854, 10.04
3.587273, 7.41
5.342622, 135.58
7.682192, 10.04
8.947719, 135.58
10.70679, 7.41
12.94711, 6.66
14.21456, 6.47
15.48118, 102.93
18.74924, 131.67
20.99118, 7.3
21.77326, 9.65
25.52709, 138.36
27.76692, 7.41
28.54338, 10.04
30.30227, 7.41
31.5711, 7.41
32.78831, 135.57
33.56652, 10.04
34.25069, 7.41
37.56762, 7.41
38.34549, 7.4
40.53939, 9.89
40.83278, 6.72
41.61178, 6.46
42.87929, 103.97
44.63388, 7.03
« Last Edit: January 16, 2018, 11:39:30 pm by Iagash »
 
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Offline joeqsmith

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Re: EEVblog 121GW Multimeter Issues
« Reply #50 on: January 12, 2018, 05:11:23 am »
Hi Dave,

I also got my meter today. Thanks for your effort. I like the probes and the build quality. I have no equipment to test its precision.

Firmware version is: U-1.02

Here are the things I don't like or consider a fault:

.....
Thanks for your time.   Could you please try logging to the SC card for a longer period, say six hours or even 24?  Also, assuming your skill level is up to it, could you try measuring power with line voltages?  Please don't attempt that if you don't have the skill set and are comfortable with it.  The reason I ask is that I had ran into problems with both of these cases and am curious if they have been addressed.   I think the prototype would hang when writing to the card after a few hours was all and the power measurement was limited to 50V or so.   

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

Offline firewalker

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Re: EEVblog 121GW Multimeter Issues
« Reply #51 on: January 12, 2018, 05:15:19 am »
Did anyone checked the quality of the contacts in the rotary switch?

Alexander.
Become a realist, stay a dreamer.

 

Offline Iagash

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Re: EEVblog 121GW Multimeter Issues
« Reply #52 on: January 12, 2018, 06:13:09 am »
Hi joeqsmith,

yes, I can handle line voltages and do so regularly.

Do you think it's related to spikes on the mains? I usually use a 0-300V 6A insulating transformer for tests like this, but if you think it makes sense I can test directly on mains but have only 230V available then. So your request would be >50VA for >6h logging to SD-card? Resistive load would be fine (they are more quiet)?

I will run it over night and hope it doesn't burn down the house. :-)

Just tell me if with or without the transformer.
« Last Edit: January 12, 2018, 06:15:56 am by Iagash »
 

Offline Iagash

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Re: EEVblog 121GW Multimeter Issues
« Reply #53 on: January 12, 2018, 06:48:09 am »
Hi firewalker,

yes, I took it appart after I noticed the issue.

Contacts look fine there are 4 of them, two on each side of the axis, each with two contact points.
They look "goldish" the pcb also looks like ENIG finish. All looks good, so I have no idea why it happens.
 

Offline exe

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Re: EEVblog 121GW Multimeter Issues
« Reply #54 on: January 12, 2018, 06:51:31 am »
They look "goldish" the pcb also looks like ENIG finish. All looks good, so I have no idea why it happens.

May be they don't reach well the pcb?
 

Offline joeqsmith

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Re: EEVblog 121GW Multimeter Issues
« Reply #55 on: January 12, 2018, 06:54:00 am »
Hi joeqsmith,

yes, I can handle line voltages and do so regularly.

Do you think it's related to spikes on the mains? I usually use a 0-300V 6A insulating transformer for tests like this, but if you think it makes sense I can test directly on mains but have only 230V available then. So your request would be >50VA for >6h logging to SD-card? Resistive load would be fine (they are more quiet)?

I will run it over night and hope it doesn't burn down the house. :-)

Just tell me if with or without the transformer.

I was checking the power using an arb, amplifier and transformer coupled.  It seems like it was limited to 50V when I started to turn it up.  You don't need a lot of current.  Obviously the meter has no problems reading just voltage.  It was tied to the power measurement.   

The data logging problem I don't think was mode specific.  I was wanting to run a stability test and had the input pins shorted or some voltage reference attached to it.   I tried recording  24 hours and when I checked it, the card only had a few points.  I tried different sample rates and such but it seemed like there was maybe a delay and timeout when recording to the card and it would just stop recording.   I want to say I tried to narrow down how long it took to fault out and it was maybe two hours.   

So just a quick test at for the AC VA mode and a short or something for the long term so we don't burn down the house. 

Thanks again for looking into this.
How electrically robust is your meter?? http://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 

Offline Iagash

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Re: EEVblog 121GW Multimeter Issues
« Reply #56 on: January 12, 2018, 07:30:29 am »

I was checking the power using an arb, amplifier and transformer coupled.  It seems like it was limited to 50V when I started to turn it up.  You don't need a lot of current.  Obviously the meter has no problems reading just voltage.  It was tied to the power measurement.

You are completely right. The display switches to OFL when I exceed a voltage of 55V AC.

I can't test with DC as my power supply has max 32V.

Can someone else please check VA mode with more than 55V DC?

I will run the logging over night.
 

Offline Iagash

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Re: EEVblog 121GW Multimeter Issues
« Reply #57 on: January 12, 2018, 07:49:59 am »
They look "goldish" the pcb also looks like ENIG finish. All looks good, so I have no idea why it happens.

May be they don't reach well the pcb?

I don't think so. In that case the meter would also show odd behavior during operation when you touch the switch which is not the case.
I'd rather guess it might be an debouncing issue in the firmware.
 

Offline amspire

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Re: EEVblog 121GW Multimeter Issues
« Reply #58 on: January 12, 2018, 07:58:11 am »
If you change to mVA/VA to manual ranges, you realize there are only 4 combinations available:

mVA mode:
5.5V + 5.5mA
55V + 5.5mA
5.5V + 55mA
55V + 55mA


VA mode:
5.5V + 550mA
55V + 550mA
5.5V + 10A
55V + 10A

Definitely the whole VA feature is underveloped. If I was logging VA, I would definitely want to use a manual range to avoid any autoranging during logging.
« Last Edit: January 12, 2018, 08:00:37 am by amspire »
 

Offline amspire

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Re: EEVblog 121GW Multimeter Issues
« Reply #59 on: January 12, 2018, 08:20:06 am »
In lowZ mode the meter only starts to display a value >0 when the voltage rises to around 11.5V. When the voltage is lowered from 12V it works down to around 3V. If this is expected behaviour, it should be documented in the manual.
I haven't had a meter with a Low Z mode so I am not familiar with how it is meant to work. It seems to be trying to autodetect whether the input is AC or DC and it needs at least 12V to do this. It has no ranges so I assume the 550V range is fixed. The Low Z input resistance looks to be about 2.7K ohms which would dissipate 112W at 550V!

To limit dissipation to, say, 5W, then you are limited to around 110V maximum. At 240V, the dissipation would be 21W which is a lot of heat to be contained inside the meter. You could do a quick measurement, but a long term measurement would be really cooking the insides of the meter.

I think I will be replacing the 2.7K resistors with something much larger. 27K or higher. This seems like a dangerous feature as it is right now. Like the VA mode, very underveloped as you can see from the lack of documentation and specifications in the manual.
« Last Edit: January 12, 2018, 08:25:48 am by amspire »
 

Offline idpromnut

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Re: EEVblog 121GW Multimeter Issues
« Reply #60 on: January 12, 2018, 08:32:01 am »
In lowZ mode the meter only starts to display a value >0 when the voltage rises to around 11.5V. When the voltage is lowered from 12V it works down to around 3V. If this is expected behaviour, it should be documented in the manual.
I haven't had a meter with a Low Z mode so I am not familiar with how it is meant to work. It seems to be trying to autodetect whether the input is AC or DC and it needs at least 12V to do this. It has no ranges so I assume the 550V range is fixed. The Low Z input resistance looks to be about 2.7K ohms which would dissipate 112W at 550V!

To limit dissipation to, say, 5W, then you are limited to around 110V maximum. At 240V, the dissipation would be 21W which is a lot of heat to be contained inside the meter. You could do a quick measurement, but a long term measurement would be really cooking the insides of the meter.

I think I will be replacing the 2.7K resistors with something much larger. 27K or higher. This seems like a dangerous feature as it is right now. Like the VA mode, very underveloped as you can see from the lack of documentation and specifications in the manual.

My Aglient U1232A has an impedance of 3.6kOhm on its LowZ mode. I think 2.7kOhm on the 121GW is fine.
 

Offline amspire

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Re: EEVblog 121GW Multimeter Issues
« Reply #61 on: January 12, 2018, 08:43:03 am »
In lowZ mode the meter only starts to display a value >0 when the voltage rises to around 11.5V. When the voltage is lowered from 12V it works down to around 3V. If this is expected behaviour, it should be documented in the manual.
I haven't had a meter with a Low Z mode so I am not familiar with how it is meant to work. It seems to be trying to autodetect whether the input is AC or DC and it needs at least 12V to do this. It has no ranges so I assume the 550V range is fixed. The Low Z input resistance looks to be about 2.7K ohms which would dissipate 112W at 550V!

To limit dissipation to, say, 5W, then you are limited to around 110V maximum. At 240V, the dissipation would be 21W which is a lot of heat to be contained inside the meter. You could do a quick measurement, but a long term measurement would be really cooking the insides of the meter.

I think I will be replacing the 2.7K resistors with something much larger. 27K or higher. This seems like a dangerous feature as it is right now. Like the VA mode, very underveloped as you can see from the lack of documentation and specifications in the manual.

My Aglient U1232A has an impedance of 3.6kOhm on its LowZ mode. I think 2.7kOhm on the 121GW is fine.
But how does it work? Is it a PTC thermistor and not a 2k7 resistor? I was just looking at the Fluke 114 manual and its LowZ goes to 600V and has about a 3K impedance. It better be a PTC thermistor, because 120W of heat inside a multimeter is a massive problem.
 

Online EEVblog

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Re: EEVblog 121GW Multimeter Issues
« Reply #62 on: January 12, 2018, 08:45:43 am »
In lowZ mode the meter only starts to display a value >0 when the voltage rises to around 11.5V. When the voltage is lowered from 12V it works down to around 3V. If this is expected behaviour, it should be documented in the manual.
I haven't had a meter with a Low Z mode so I am not familiar with how it is meant to work. It seems to be trying to autodetect whether the input is AC or DC and it needs at least 12V to do this. It has no ranges so I assume the 550V range is fixed. The Low Z input resistance looks to be about 2.7K ohms which would dissipate 112W at 550V!

No! That's not how this meter or any other Low-Z meter works.
The "resistor" is actually a PTC themristor, it's resistance increases when it heats up.
 

Offline Iagash

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Re: EEVblog 121GW Multimeter Issues
« Reply #63 on: January 12, 2018, 08:48:48 am »
I think I will be replacing the 2.7K resistors with something much larger. 27K or higher. This seems like a dangerous feature as it is right now. Like the VA mode, very underveloped as you can see from the lack of documentation and specifications in the manual.

No, the lowZ mode seems fine apart from the low sensitivity. It consumes around 5mA at 12V AC input voltage.
If I ramp up the voltage very quickly to 310V AC it consumes a maximum of 245mA for a very short time and drops immediately to around 3mA which is a power consumption of about 1W.
So I guess everything is save.
 

Offline amspire

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Re: EEVblog 121GW Multimeter Issues
« Reply #64 on: January 12, 2018, 08:53:03 am »
In lowZ mode the meter only starts to display a value >0 when the voltage rises to around 11.5V. When the voltage is lowered from 12V it works down to around 3V. If this is expected behaviour, it should be documented in the manual.
I haven't had a meter with a Low Z mode so I am not familiar with how it is meant to work. It seems to be trying to autodetect whether the input is AC or DC and it needs at least 12V to do this. It has no ranges so I assume the 550V range is fixed. The Low Z input resistance looks to be about 2.7K ohms which would dissipate 112W at 550V!

No! That's not how this meter or any other Low-Z meter works.
The "resistor" is actually a PTC themristor, it's resistance increases when it heats up.
Thanks. Even Fluke didn't bother to explain that in their manual. I guess it is one of those things that you are just meant to know.
 

Online EEVblog

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Re: EEVblog 121GW Multimeter Issues
« Reply #65 on: January 12, 2018, 09:01:34 am »
NOTE: Can we please limit this thread to reporting and confirmation of bugs and issues, any discussions should be on the discussion thread.
Thanks.
 
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Offline amspire

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Re: EEVblog 121GW Multimeter Issues
« Reply #66 on: January 12, 2018, 09:09:28 am »
NOTE: Can we please limit this thread to reporting and confirmation of bugs and issues, any discussions should be on the discussion thread.
Thanks.
I think we have been doing that. If I crossed a line by not understanding the undocumented low Z mode, I apologize.
 

Offline massivephoton

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Re: EEVblog 121GW Multimeter Issues
« Reply #67 on: January 12, 2018, 09:19:06 am »
I haven't had a meter with a Low Z mode so I am not familiar with how it is meant to work. It seems to be trying to autodetect whether the input is AC or DC and it needs at least 12V to do this. It has no ranges so I assume the 550V range is fixed. The Low Z input resistance looks to be about 2.7K ohms which would dissipate 112W at 550V!

To limit dissipation to, say, 5W, then you are limited to around 110V maximum. At 240V, the dissipation would be 21W which is a lot of heat to be contained inside the meter. You could do a quick measurement, but a long term measurement would be really cooking the insides of the meter.

I think I will be replacing the 2.7K resistors with something much larger. 27K or higher. This seems like a dangerous feature as it is right now. Like the VA mode, very underveloped as you can see from the lack of documentation and specifications in the manual.

The 2k7 impedance seems to be pretty standard. Fluke 115, 116 and 117 LoZ specs indicates 3k with 500pF, as the datasheet states:
http://media.fluke.com/documents/2793260_6116_ENG_A_W.PDF

As already suggested at least here...
Probably some thermistor or similar.

Instruction Sheet for Fluke SV225 says:

Specifications
Voltages up to 1000 volts continuous can be safely applied to
the Adapter without damage.
Operation Temperature
-20 °C to +55 °C (-40 °F to 131 °F)
Altitude
2,000 Meters Operating
Humidity
90 % at 0 to 35 °C (32 °F to 95 °F), 70 % at 35 to 55 °C
(95 °F to 131 °F)
Nominal Resistance
3,000 ? @ 25 °C (77 °F)

... and here ...

I would think it uses a PTC thermistor, so it draws a semi constant power over the voltage range. You find a similar one in the cheap voltstick devices.

... and way hotter here ...

https://www.google.com/patents/US8480301

thermistors are used to limit the power.


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Offline joeqsmith

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Re: EEVblog 121GW Multimeter Issues
« Reply #68 on: January 12, 2018, 09:38:50 am »
NOTE: Can we please limit this thread to reporting and confirmation of bugs and issues, any discussions should be on the discussion thread.
Thanks.
I think we have been doing that. If I crossed a line by not understanding the undocumented low Z mode, I apologize.
I think part of the problem as well is that it's not always cut and dry if the perceived problems were not that way by design.   To me, the slow auto range was by design.  It's known and not really a bug.  For the most part, the feedback appears to be going in one of two places.   

Strange on the VA mode.   I guess I just assumed it would allow for a wider voltage range.  Keep us posted on the data logging.     
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Offline Iagash

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Re: EEVblog 121GW Multimeter Issues
« Reply #69 on: January 12, 2018, 09:21:23 pm »
Keep us posted on the data logging.   

I did run VA logging for about 9h over night.
It produced a logfile with  130662 entries, which is about 4 lines per second.
So this seems fine.

It has a small display glitch during logging. The "k" symbol behind the record counter in the upper display is flickering.

As I stated in my previous post the bargraph is also flickering some times when two values are measured, so I guess there are some race conditions in the display update code of the firmware or they didn't use double buffering for the display.

Quote
mm@ovid:~/121gw$ head -10 18011200.CSV ; echo "[...]" ; tail -10 18011200.CSV
START,2018/01/12,01:48:47,
ID,170800000,
INTERVAL,000,sec,
,MAIN,,,SUB-1,,,SUB-2,,,Remark,
No. ,Func. ,Value,Unit,Func. ,Value,Unit,Func. ,Value,Unit,
1,DCVA,00000.0,mVA,DCV,00.0001,V,DCA,-0001.41,mA,,
2,DCVA,00000.0,mVA,DCV,00.0001,V,DCA,-0001.41,mA,,
3,DCVA,00000.0,mVA,DCV,00.0001,V,DCA,-0001.41,mA,,
4,DCVA,00000.0,mVA,DCV,00.0001,V,DCA,-0001.41,mA,,
5,DCVA,00000.0,mVA,DCV,00.0001,V,DCA,-0001.41,mA,,
[...]
130656,DCVA,01292.9,mVA,DCV,03.2999,V,DCA,0391.83,mA,,
130657,DCVA,01292.9,mVA,DCV,03.2999,V,DCA,0391.83,mA,,
130658,DCVA,01292.9,mVA,DCV,03.2999,V,DCA,0391.81,mA,,
130659,DCVA,01292.9,mVA,DCV,03.2999,V,DCA,0391.81,mA,,
130660,DCVA,01292.9,mVA,DCV,03.2999,V,DCA,0391.81,mA,,
130661,DCVA,01292.9,mVA,DCV,03.2999,V,DCA,0391.81,mA,,
130662,DCVA,01292.9,mVA,DCV,03.2999,V,DCA,0391.81,mA,,
MAX,49,DCVA,01294.1,mVA,
MIN,1,DCVA,00000.0,mVA,

Should I try something else?
« Last Edit: January 12, 2018, 09:34:24 pm by Iagash »
 

Offline Iagash

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Re: EEVblog 121GW Multimeter Issues
« Reply #70 on: January 12, 2018, 09:30:37 pm »
I found something else with logging.

If you long press [MEM] in Ohm mode (no matter if AUTO or MANUAL range) the meter crashes immediately.
Only turning it OFF and ON again brings it back.


Forget  it. It was my stupidity. I had the SD-card still in my desktop.
So the bug now is:

The meter crashes if you enable logging without a SD-card present.

And another one:

Autoranging doesn't work when logging to SD-card and it stays disabled even after you switch off logging but it is displayed the whole time on the display as enabled. You have to long press the RANGE button to get it working again.

I added both issues to post http://www.eevblog.com/forum/testgear/eevblog-121gw-multimeter-issues/msg1397729/#msg1397729
« Last Edit: January 12, 2018, 09:51:54 pm by Iagash »
 

Offline fanOfeeDIY

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EEVblog 121GW Multimeter Issues
« Reply #71 on: January 12, 2018, 11:14:58 pm »
I am not sure this is the how it is designed or a bug.

When I was reviewing the 121GW meter, almost every time I turn the knob from OFF to Low-Z, the back-light flickers.

The back-light going on for about 0.1 sec seems to consume battery every time start using the meter.

The firmware version is 1.01.

I uploaded the video of back-light flashing at the bellow link.
« Last Edit: January 12, 2018, 11:35:06 pm by fanOfeeDIY »
 

Offline Iagash

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Re: EEVblog 121GW Multimeter Issues
« Reply #72 on: January 12, 2018, 11:25:51 pm »
When I was reviewing the 121GW meter, almost every time I turn the knob from OFF to Low-Z, the back-light flickers.

The back-light going on for about 0.1 sec seems to consume battery consumtion every time start using the meter.

Confirmed with Firmware U-1.02.
It blinks always when it is switched on from any of the "OFF" positions, but it doesn't blink when turning on again from auto power off.

I guess it's related to the micro controller initialization on a cold boot.

The power consumption for this should be negligible, so I'd say it'a purely cosmetic issue, if at all.
« Last Edit: January 12, 2018, 11:54:47 pm by Iagash »
 

Offline fanOfeeDIY

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EEVblog 121GW Multimeter Issues
« Reply #73 on: January 12, 2018, 11:27:52 pm »
Another point I found was when I was doing the overnight SD card data logging.
one of the file had garbled data in the file, when I was testing for the thread in the forum.

http://www.eevblog.com/forum/testgear/new-eevblog-branded-multimeter-coming/msg1398530/#msg1398530

The data is corrupted as bellow in the middle of the data.
59625,DCV,049.997,V,,,,,,,,
59626,DCV,049.997,V,,,,,,,,
59627,DCV,049.996,V,,,,,,,,
59628,DCV,049.997,V,,,,,,,,
59629,DCV,                                                                                                                                                                                        59641,DCV,050.001,V,,,,,,,,
59642,DCV,049.996,V,,,,,,,,
59643,DCV,049.996,V,,,,,,,,
59644,DCV,049.998,V,,,,,,,,
59645,DCV,049.996,V,,,,,,,,

The garbled line only happened in one line out of four files of data logging.
The other three files had no issue.

The firmware is 0.01 and the SD card is the SunDisk which is included in the meter as a factory default.

I attached the original file with zip compression to work around the file size limitation on the forum.

Hope these report help improving the meter.
« Last Edit: January 13, 2018, 12:10:19 am by fanOfeeDIY »
 

Offline firewalker

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Re: EEVblog 121GW Multimeter Issues
« Reply #74 on: January 12, 2018, 11:32:26 pm »
Maybe a self test thing? Like show all segments and test the back light?
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Offline joeqsmith

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Re: EEVblog 121GW Multimeter Issues
« Reply #75 on: January 13, 2018, 12:02:58 am »
I did run VA logging for about 9h over night.
It produced a logfile with  130662 entries, which is about 4 lines per second.
So this seems fine.

Should I try something else?


Thanks for running these longer tests!  I know a bit of a pain.   Glad to hear they have it working.   It's been some time since I did anything with the prototype and I can't remember any other real major functional problems with it.  I remember most were simple problems.   If you check my main thread where I post my results, some of the problems were discussed there but my guess is they have been corrected.   

What's the open circuit HV diode test putting out now? 
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Offline Iagash

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Re: EEVblog 121GW Multimeter Issues
« Reply #76 on: January 13, 2018, 12:16:04 am »
What's the open circuit HV diode test putting out now?

17.332V
 

Offline joeqsmith

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Re: EEVblog 121GW Multimeter Issues
« Reply #77 on: January 13, 2018, 01:43:50 am »
What's the open circuit HV diode test putting out now?
17.332V
That's interesting.  I think the prototype was under 17.   I was a bit concerned with the mux they were using had an absolute max rating.  It looked like they stayed with the same part in Dave's close up video showing the board.   Maybe they came up with a better way to protect it.   From what I saw, the mux was the weak point as far as the transient tests I run.    That mux is an HEFxxxx  located near the edge of the PCB if you wanted to pull the datasheets to have a look.   I think its an absolute max of 18 on that one.  You can drive it a little above the rail.   Easy enough to trace the path to the input pin to see how it is being protected.   Again, hard to say if you would call it a bug or issue anyway.  Maybe just something to be aware of.   
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Online Scottjd

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Re: EEVblog 121GW Multimeter Issues
« Reply #78 on: January 13, 2018, 01:59:55 am »
What's the open circuit HV diode test putting out now?
17.332V
That's interesting.  I think the prototype was under 17.   I was a bit concerned with the mux they were using had an absolute max rating.  It looked like they stayed with the same part in Dave's close up video showing the board.   Maybe they came up with a better way to protect it.   From what I saw, the mux was the weak point as far as the transient tests I run.    That mux is an HEFxxxx  located near the edge of the PCB if you wanted to pull the datasheets to have a look.   I think its an absolute max of 18 on that one.  You can drive it a little above the rail.   Easy enough to trace the path to the input pin to see how it is being protected.   Again, hard to say if you would call it a bug or issue anyway.  Maybe just something to be aware of.   
Good question, it was claimed to be 15V, so if it has the room maybe a good TVS diode could go in and even with the voltage drop it would still be above 15V. But I don’t know if a TVS diode would even stop your transients Joe. But it would be better then nothing.
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Online dr.diesel

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Re: EEVblog 121GW Multimeter Issues
« Reply #79 on: January 13, 2018, 02:02:20 am »
What's the open circuit HV diode test putting out now?

17.332V

000063 = 16.3V
000061 = 17.8V

Offline mikeselectricstuff

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Re: EEVblog 121GW Multimeter Issues
« Reply #80 on: January 13, 2018, 02:04:49 am »
What's the open circuit HV diode test putting out now?

17.332V

000063 = 16.3V
000061 = 17.8V
Is it significantly dependent on battery voltage ?
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Online dr.diesel

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Re: EEVblog 121GW Multimeter Issues
« Reply #81 on: January 13, 2018, 02:09:57 am »
Bug, FW 1.01.

Switching to diode test mode, the secondary display continues to show temp, not 3/15v like it should, until the Range button is cycled.

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Re: EEVblog 121GW Multimeter Issues
« Reply #82 on: January 13, 2018, 02:17:50 am »
What's the open circuit HV diode test putting out now?

17.332V

000063 = 16.3V
000061 = 17.8V
Is it significantly dependent on battery voltage ?

From 5-6.5V battery voltage has no impact.

Offline hwti

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Re: EEVblog 121GW Multimeter Issues
« Reply #83 on: January 13, 2018, 02:30:27 am »
What's the open circuit HV diode test putting out now?

17.332V
Here 15.45V (and 3.23V for the 3V mode), FW 1.02
 

Offline hwti

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Re: EEVblog 121GW Multimeter Issues
« Reply #84 on: January 13, 2018, 02:44:49 am »
  • The range switch is unreliable, you sometimes need to poke it a bit until the meter behaves properly.
  • The inability to disable the excessive beeping or at least lowering the volume get's annoying fast.
  • Autoranging speed in Ohms is way too slow.

I just had the range switch issue : after switching from V to Low-Z, it stayed in volts mode, I had to move the switch a little bit.

+1 for the annoying beeps and slow autoranging
 

Offline lewis

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Re: EEVblog 121GW Multimeter Issues
« Reply #85 on: January 13, 2018, 04:08:02 am »
Beep beep. Beep. Beep. Beep. Beep!

FOR THE LOVE OF GOD....

Skip to 6min 32sec


« Last Edit: January 13, 2018, 04:11:30 am by lewis »
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Offline joeqsmith

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Re: EEVblog 121GW Multimeter Issues
« Reply #86 on: January 13, 2018, 11:38:51 am »
What's the open circuit HV diode test putting out now?
17.332V
That's interesting.  I think the prototype was under 17.   I was a bit concerned with the mux they were using had an absolute max rating.  It looked like they stayed with the same part in Dave's close up video showing the board.   Maybe they came up with a better way to protect it.   From what I saw, the mux was the weak point as far as the transient tests I run.    That mux is an HEFxxxx  located near the edge of the PCB if you wanted to pull the datasheets to have a look.   I think its an absolute max of 18 on that one.  You can drive it a little above the rail.   Easy enough to trace the path to the input pin to see how it is being protected.   Again, hard to say if you would call it a bug or issue anyway.  Maybe just something to be aware of.   
Good question, it was claimed to be 15V, so if it has the room maybe a good TVS diode could go in and even with the voltage drop it would still be above 15V. But I don’t know if a TVS diode would even stop your transients Joe. But it would be better then nothing.

I assume 15 would be the minimum.  It really would not matter to me anyway, if it ran a little hot (higher).  Actually, I would prefer it.   It the part has an absolute max of 18 and they are running it a bit over 17, there is not a lot of wiggle room.  You don't want it to leak and you don't ever want to exceed that absolute value.   I don't know if they made improvements to the released meter or not and am only assuming it's the same based on the comments.   They may have found a better way to protect it.   

There was a third video of my final mods as well. I damaged that prototype a few times before settling in on part selection.  I don't remember how high I went up to with it before calling it good enough.  I can tell you I never put the grim reaper on it with 14KV or bust.   :-DD       
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Offline ChrisG

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Re: EEVblog 121GW Multimeter Issues
« Reply #87 on: January 13, 2018, 10:58:53 pm »
Received mine on 12th Jan in Netherlands. Auto ranging is ridicuously slow. None of my other DMM’s 869, 235 and an old Metrixc 53c are so slow. Is this an issue or by design?

Apologies.  Just noticed it has been mentioned already many times. V 1.02 is my firmware. Will do more tests later.
« Last Edit: January 13, 2018, 11:16:31 pm by ChrisG »
 

Offline joeqsmith

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Re: EEVblog 121GW Multimeter Issues
« Reply #88 on: January 14, 2018, 04:35:22 am »
When I first released that video where I had repaired the prototype meter the first time, someone had commented how the period calculation was not correct and I explained how I look for a deviation in how the meter behaves and with it being a prototype, I was expecting some problems.  I assume people have checked the basic functions like this to make sure they now work.   

Has anyone checked to see if they still limit the frequency counter to 1MHz?   Again, not really a bug perhaps but more a slight oversight.   
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Offline mikeselectricstuff

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Re: EEVblog 121GW Multimeter Issues
« Reply #89 on: January 14, 2018, 07:03:35 am »
Has anyone checked to see if they still limit the frequency counter to 1MHz?   Again, not really a bug perhaps but more a slight oversight.
Or maybe there are issues like jitter or miscounts that make higher frequencies subject to errors?
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Offline joeqsmith

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Re: EEVblog 121GW Multimeter Issues
« Reply #90 on: January 14, 2018, 07:07:00 am »
Has anyone checked to see if they still limit the frequency counter to 1MHz?   Again, not really a bug perhaps but more a slight oversight.
Or maybe there are issues like jitter or miscounts that make higher frequencies subject to errors?

If you watch the video, it just over ranges.  They cap it for some reason. 
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Offline hwti

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Re: EEVblog 121GW Multimeter Issues
« Reply #91 on: January 14, 2018, 07:47:21 am »
Has anyone checked to see if they still limit the frequency counter to 1MHz?   Again, not really a bug perhaps but more a slight oversight.
It's still limited.
It's in the manual : "99.999 Hz to 999.99 kHz" ranges.
 

Offline The Soulman

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Re: EEVblog 121GW Multimeter Issues
« Reply #92 on: January 14, 2018, 08:29:59 am »
NOTE: Can we please limit this thread to reporting and confirmation of bugs and issues, any discussions should be on the discussion thread.
Thanks.
No point in making a point just to make a point, that would be pointless.
 

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Re: EEVblog 121GW Multimeter Issues
« Reply #93 on: January 14, 2018, 11:21:52 am »
NOTE: Can we please limit this thread to reporting and confirmation of bugs and issues, any discussions should be on the discussion thread.
Thanks.
I didn’t know we were keeping score.
One point to you!
Who is winning?

Wait, that’s your signature, not your post. That doesn’t count then.
So if this is the bugs only (some know about before the release and never fixed?) the What thread is the shipping only? Does anyone know, I tried searching but their is so many threaded mentioning the 121GW in then. Most old threads before the Kickstarter even launched.
« Last Edit: January 14, 2018, 11:26:20 am by Scottjd »
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Offline The Soulman

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Re: EEVblog 121GW Multimeter Issues
« Reply #94 on: January 14, 2018, 11:48:24 am »
Well maybe this one is actually monitored by Dave and he gets a notification for every single reply here so he can gather data
to form statistics and eventually can act accordingly?
Don't pollute it.
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Re: EEVblog 121GW Multimeter Issues
« Reply #95 on: January 14, 2018, 12:15:35 pm »
For those looking for another place to post, there is a discussion thread up and running on the meter here!
http://www.eevblog.com/forum/testgear/eevblog-121gw-discussion-thread/
 

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Re: EEVblog 121GW Multimeter Issues
« Reply #96 on: January 14, 2018, 12:49:01 pm »
I can aslo confirm that v1.02 autoranging is very slow, especially measuring low ohms or higher voltages. Compared to BM235 its about 16 times slower worst case (0.5s vs 8s, short circuit measurement) which makes those modes basically unusable at the moment. I'm expecting this should be easily fixable in firmware so not too worried, just looks like it's always measuring at full precision starting from Mohms range and not doing fast range checking measurments at first.
 

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Re: EEVblog 121GW Multimeter Issues
« Reply #97 on: January 15, 2018, 02:49:15 am »
@Dave: when you get the chance, can you see about getting the firmware update v1.02 published for those of us that have only v1.01?  Thanks!
 

Offline nuclearcat

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Re: EEVblog 121GW Multimeter Issues
« Reply #98 on: January 15, 2018, 04:26:48 am »
BLE data corruption issue:
Code: [Select]
#!/usr/bin/python
from bluepy import btle
from bluepy.btle import UUID, Peripheral,DefaultDelegate
import binascii
import array
from struct import *

def parse_data(x):
    xlen = len(x)
    for offset in range(0,xlen):
        if (ord(x[offset:offset+1]) == 0xF2):
            # Process accumulated data
            print ("Accumulated data(%d): %s" % (len(parse_data.accumulated_data), str(parse_data.accumulated_data)))
            parse_data.accumulated_data = array.array('c')
        else:
            parse_data.accumulated_data.append(x[offset:offset+1])

class MyDelegate(btle.DefaultDelegate):
    def __init__(self):
        btle.DefaultDelegate.__init__(self)

    def handleNotification(self, cHandle, data):
         parse_data(data)


parse_data.accumulated_data = array.array('c')
# Put your multimeter mac here
p = btle.Peripheral("88:6B:XX:XX:XX:XX", btle.ADDR_TYPE_PUBLIC)
p.setDelegate( MyDelegate() )

print('Ready!')
p.writeCharacteristic(0x9, "\x03\x00")

while True:
    if p.waitForNotifications(1.0):
        continue

    print("Waiting...")

with this script it is easy to reproduce data corruption over BLE, length is changing and bits are flipping.
For example:
Code: [Select]
31373038303030303030313031343041451b34303130304537303130383038343030303030300a
3137303830303030303031300c343041453634303130304537303130383038343030303030300a
31373038303030303030313031343041453634303130304537303130383038343030303030300a
31373038303030303030313031343041453634303130304537303130383038343030303030300a
31373038303030303030313031343041453607303834303030303030303030303030303030300a
31373038303030303030313031343041450d74373031303830383430303030303030303030300a
3137303830303030303031303134304145360a
31370638303030303030313031343041453634303130304537303130383038343030303030300a <-- here is a "06" at pos 5,6 where I expected "30"
31373038303030303030313031343041453634303130304537303106383038343030303030300a
31373038303030303030313031343041453634303130534537303130383038343030303030300a
31373038303030303030313031343041453634303130304537303130383038343030303030300a
3137303830303030303031303134304145360c304537303130383038343030303030303030300a
3137303830303030303031303134304145360630303030303030303030303032440d0a
313730383030303030303130313430414536343031300a
31373038303030303030313031343041453634303130304537303130383038343030303030300a
31373038303030303030313031343041453634300330304537303130383038343030303030300a
31373038303030303030313031343041453634303130304537303130383038343030303030300a
31373038303030303030313031343041453634303130304537303130383038343030303030300a
31373038303030303030313031343041453634303130304537303130383038343030303030300a
31373038303030303030313031343041453681303030303030303030303030303030303030300a
313730383030303030303130313430414536303032440d0a
3137303830303030303031303134304145363430313030453730313038303834300a
31373038303030303030313031343041453634303130304537303130383038343030303030300a
31373038303030303030313031343041453634303130304537303130383038341830303030300a
 

Online IanB

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Re: EEVblog 121GW Multimeter Issues
« Reply #99 on: January 15, 2018, 04:53:25 am »
The data is corrupted as bellow in the middle of the data.
59625,DCV,049.997,V,,,,,,,,
59626,DCV,049.997,V,,,,,,,,
59627,DCV,049.996,V,,,,,,,,
59628,DCV,049.997,V,,,,,,,,
59629,DCV,                                                                                                                                                                                        59641,DCV,050.001,V,,,,,,,,
59642,DCV,049.996,V,,,,,,,,
59643,DCV,049.996,V,,,,,,,,
59644,DCV,049.998,V,,,,,,,,
59645,DCV,049.996,V,,,,,,,,

The garbled line only happened in one line out of four files of data logging.

It looks to me as if samples 59629 through 59640 are missing from the file? So it's not just a garbled line, it's some dropped data.
I'm not an EE--what am I doing here?
 
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Offline fanOfeeDIY

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Re: EEVblog 121GW Multimeter Issues
« Reply #100 on: January 15, 2018, 02:07:35 pm »
The data is corrupted as bellow in the middle of the data.
59625,DCV,049.997,V,,,,,,,,
59626,DCV,049.997,V,,,,,,,,
59627,DCV,049.996,V,,,,,,,,
59628,DCV,049.997,V,,,,,,,,
59629,DCV,                                                                                                                                                                                        59641,DCV,050.001,V,,,,,,,,
59642,DCV,049.996,V,,,,,,,,
59643,DCV,049.996,V,,,,,,,,
59644,DCV,049.998,V,,,,,,,,
59645,DCV,049.996,V,,,,,,,,

The garbled line only happened in one line out of four files of data logging.

It looks to me as if samples 59629 through 59640 are missing from the file? So it's not just a garbled line, it's some dropped data.

Good comment, I should have attached the raw data of the log file from the beginning why I thought it was a garbled line.

I just opened the file with binary editor.
Attached is the screen shot when opening the log file with binary editor.
0x00 is not in ASCII code.

This is my pure guess based on my software engineering experience. The firmware is trying to write the data to SD card however it could be it has memory writing over flow, memory leak or improper locking between other threads.

« Last Edit: January 15, 2018, 02:10:22 pm by fanOfeeDIY »
 
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Offline iainwhite

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Re: EEVblog 121GW Multimeter Issues
« Reply #101 on: January 16, 2018, 03:07:31 am »
My issues:

1. The manual is not very clear on the type of Setup button press that is needed e.g. long press to save a value after editing it.
2. The constant beeping is driving me mad. Please can we have an option to turn off the beeper.

I realize that both these issues have already been reported.
 

Online EEVblog

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Re: EEVblog 121GW Multimeter Issues
« Reply #102 on: January 16, 2018, 05:03:06 pm »
Seems like YOU are the one polluting it.  Have anything technical to add?

I'll be very clear again.
This thread is for REPORTS of bugs and issues and CONFIRMATIONS of those bugs and issues.
DO NOT discuss them here, PLEASE!
 

Offline amspire

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Re: EEVblog 121GW Multimeter Issues
« Reply #103 on: January 16, 2018, 05:36:11 pm »
Addition to Dec 11th Manual:

Firmware Version 1.01 has an extra setup field "00000" not mentioned in the manual. It is between the hour-minute setting and logging interval setting.

I gather it is a programmable Serial number or ID number used in Bluetooth communication to identify a meter.
 
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Offline joeqsmith

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Re: EEVblog 121GW Multimeter Issues
« Reply #104 on: January 16, 2018, 08:11:46 pm »
Seems like YOU are the one polluting it.  Have anything technical to add?

I'll be very clear again.
This thread is for REPORTS of bugs and issues and CONFIRMATIONS of those bugs and issues.
DO NOT discuss them here, PLEASE!


I did not realize you were censoring posts in this area.   I resubmitted the post you removed twice because I literally thought I had forgotten to press the send key, not because I was trying to be a dick about it.     
How electrically robust is your meter?? http://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 

Offline lewis

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Re: EEVblog 121GW Multimeter Issues
« Reply #105 on: January 17, 2018, 12:24:12 am »
...CONFIRMATIONS of those bugs and issues.

I can confirm the meter beeps and beeps and beeps and beeps and beeps and beeps and BEEEEEEEPPPPS which makes it basically unusable, because I BEEP, I mean keep, wanting to throw it at great BEEP, I mean speed, across the workBEEP, I mean workshop. I've taken back off and covered the sounder in many layers of tape but it's still annoying as hell.

I can also confirm It also takes about 9 seconds to measure a low resistance. The fuse rating printed on the back label does not match the fuse inside (440mA 1kV vs 400mA 600V). Update rate on the bluetooth app is abysmal, and the connection keeps dropping out. I don't know if the measurement displayed on the smartphone is what the meter is actually measuring, or if the connection has died.

If I remember correctly, there is also a large-ish offset under an open-probe condition on AC and DC voltage ranges (will edit this post later when I have the meter in my hand to confirm). Nope! mV range was showing on display, but selector switch was set to V! Had a -0.5mV DC offset, thought it was -0.5V. I think I had a dicky selector switch, very difficult to reproduce now the switch has had some (ab)use.

Dave, I can't see how you would have approved the prototype and thought it acceptable.

Beep <shudder>
« Last Edit: January 17, 2018, 02:27:15 am by lewis »
I will not be pushed, filed, stamped, indexed, briefed, debriefed or numbered.
 

Offline exe

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Re: EEVblog 121GW Multimeter Issues
« Reply #106 on: January 17, 2018, 03:10:27 am »
Firmware Version 1.01 has an extra setup field "00000" not mentioned in the manual. It is between the hour-minute setting and logging interval setting.

I thought it's a logging interval or screen refresh interval in ms... Or a sample number... Uhm...
 

Offline MatthewEveritt

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Re: EEVblog 121GW Multimeter Issues
« Reply #107 on: January 17, 2018, 03:59:15 am »
It's apparently a sort of 'serial number' that gets added to the bluetooth data to help distinguish multiple meters [source].
 

Offline Iagash

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Re: EEVblog 121GW Multimeter Issues
« Reply #108 on: January 18, 2018, 03:14:05 am »
While I consider the autoranging speed not particularly good, it is at least correct and works.

The fails in the adnvanced functions, that distinguish this meter from the rest of the market are much more annoying. They are not just "slow", they are plain unreliable and broken.

After fanOfeeDIY showed the broken logfile I decided to do a test to the maximum extend the meter logs.

I don't get why there is a limitation on 600k lines, but well, maybe Dave will explain some day or it's extended.
The 600k lines don't even last 48h.
I know I could reduce the log interval, but why?

I got the corrupt logfile in my first try.

The data is corrupted as bellow in the middle of the data.
59625,DCV,049.997,V,,,,,,,,
59626,DCV,049.997,V,,,,,,,,
59627,DCV,049.996,V,,,,,,,,
59628,DCV,049.997,V,,,,,,,,
59629,DCV,                                                                                                                                                                                        59641,DCV,050.001,V,,,,,,,,
59642,DCV,049.996,V,,,,,,,,
59643,DCV,049.996,V,,,,,,,,
59644,DCV,049.998,V,,,,,,,,
59645,DCV,049.996,V,,,,,,,,

The garbled line only happened in one line out of four files of data logging.

It looks to me as if samples 59629 through 59640 are missing from the file? So it's not just a garbled line, it's some dropped data.

Good comment, I should have attached the raw data of the log file from the beginning why I thought it was a garbled line.

I just opened the file with binary editor.

I can confirm the file corruption. I let the meter log for almost 2 days in VA mode and have several corrupted lines in the log.

I ran a small awk script on the file to find lines where the line counter didn't match the actual line number of the log lines.

Code: [Select]
awk -F, '/^[0-9]+,/{if ( c != $1 ) { printf("%6d %6d %s\n", l, c, $0); c = $1 } c++; l++; }BEGIN{l=1;c=1}' < 18011500.CSV
It prints the real line number, the line number it expected and the line from the logfile. The result is this:
Code: [Select]
61501  61501 61502,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,
139554 139555 139562,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,
243949 243957 243962,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,
267167 267180 267182,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,
344797 344812 344822,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,
356188 356213 356222,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,
412106 412140 412142,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,
431304 431340 431342,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,
478699 478737 478742,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,
523695 523738 523742,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,

So there are 10 errors in just one logfile.

Here are the errors:
Code: [Select]
61499,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.53,mA,,
61500,DCVA,01959.5,mVA,DC^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@61501,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,
61502,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,
Code: [Select]
139553,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.53,mA,,
139554,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,044^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@139561,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,
139562,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,
Code: [Select]
243956,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.53,mA,,
24395^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@243961,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,
243962,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,
Code: [Select]
267178,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.53,mA,,
267179,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.53,mA,^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@267181,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,
267182,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,
Code: [Select]
344810,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.53,mA,,
344811,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.53,mA,^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@344821,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,
344822,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,
Code: [Select]
356212,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.53,mA,,
35621^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@356221,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,
356222,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,
Code: [Select]
412138,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.53,mA,,
412139,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.53,mA,^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@412141,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,
412142,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,
Code: [Select]
431338,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.53,mA,,
431339,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.53,mA,^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@431341,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,
431342,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,
Code: [Select]
478735,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.53,mA,,
478736,DCVA,01959.5,mVA,DCV,0^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@478741,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,
478742,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,
Code: [Select]
523736,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.53,mA,,
523737,DCVA,01959.5,mVA,DCV,04.4482,V^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@523741,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,
523742,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,

The last logline in the file is:
Code: [Select]
600000,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.53,mA,,

So logging stops after the meter thinks it logged 600k lines, but in reality it logged only 599956 lines.

Interestingly the display counted to more than 600.00k lines. The highest value I saw on the display was 602.xxk lines (I don't remeber the xx).

So on the display it either kept counting after it stopped logging or didn't number and write all lines it actually thought it logged.

In the end there was "SDend" displayed and the "MEM" LCD-segment was not active anymore.

I can't attach the logfile since the forum says it's too big (even zipped it is 1.7MB). But I can send it to anybody who is interested.
 

Offline lowimpedance

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Re: EEVblog 121GW Multimeter Issues
« Reply #109 on: January 18, 2018, 02:14:37 pm »
Bug/mechanical issue in the Diode test mode. When selected if you jiggle the plugs at the meter you get the short double beep and sometimes a continuous beep which requires further lead or switch jiggles to stop. So the switch seems to be very sensitive mechanically to trigger the continuous beep. Also via some PCB flexing (i guess), due to the test lead plugs will also trigger the beep.

Others can test to confirm.
As Dr diesel noted the temperature display is on until the range button is pressed for either 3 or 15v test.

Also to note that continuity function sometimes does not work either(similar switch issue?).
Ohms appears unaffected by any mechanical jiggling.

firmware 1.01
You call that current ?.......
I'll show you current !
 the odd multimeter or 2 or 3 or 4...or........never mind
 

Offline amspire

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Re: EEVblog 121GW Multimeter Issues
« Reply #110 on: January 18, 2018, 03:22:00 pm »
Bug/mechanical issue in the Diode test mode. When selected if you jiggle the plugs at the meter you get the short double beep and sometimes a continuous beep which requires further lead or switch jiggles to stop. So the switch seems to be very sensitive mechanically to trigger the continuous beep. Also via some PCB flexing (i guess), due to the test lead plugs will also trigger the beep.

firmware 1.01
I do not get the jiggling issue, but for some reason, when the diode mode senses any change (like a 10K resistor or anything else), it double beeps and then a second later double beeps again. Not sure why that is wanted. If the probes are shorted, it beeps continuously just like the continuity test mode.

Also in diode mode, the bar graph seems to be not normalised for the measurement. In the default 3V diode mode, the bar graph is at 60% on open circuit. For the 15V mode, it is at 33% on open circuit. These correspond to the positions the bar graphs would be in the 5V and 50V DC ranges respectively. A minor issue, but it probably should be tidied up.

Edit: Looking closely at the bar graph and it goes from 0 to 5. So it is on 3 for the 3V range and 1.6V (16V) on the 15V diode range. I guess that makes sense.

firmware 1.01 Diode Mode
« Last Edit: January 18, 2018, 03:35:49 pm by amspire »
 

Offline lowimpedance

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Re: EEVblog 121GW Multimeter Issues
« Reply #111 on: January 18, 2018, 03:43:12 pm »
By jiggling I mean moving the lead plugs intentionally forward and back "a bit" in their sockets causes the continuous beep to engage with out shorting the probes together. And further to this once the continuous beep has started I can remove the probes from the meter and it carries on beeping until I "wiggle" the selector switch a little bit then it will stop followed with the 2 short beeps.
Unfortunately I cannot do a video which would make it very clear whats going on.
You call that current ?.......
I'll show you current !
 the odd multimeter or 2 or 3 or 4...or........never mind
 

Offline Kean

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Re: EEVblog 121GW Multimeter Issues
« Reply #112 on: January 18, 2018, 03:47:30 pm »
I tried to reproduce this "wiggling" problem in diode mode, but I can't.  Sounds like you have an intermittent internal short.  Strange if you cannot also reproduce in continuity mode.
edit: FW 1.01
 

Offline amspire

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Re: EEVblog 121GW Multimeter Issues
« Reply #113 on: January 18, 2018, 03:59:12 pm »
By jiggling I mean moving the lead plugs intentionally forward and back "a bit" in their sockets causes the continuous beep to engage with out shorting the probes together. And further to this once the continuous beep has started I can remove the probes from the meter and it carries on beeping until I "wiggle" the selector switch a little bit then it will stop followed with the 2 short beeps.
Unfortunately I cannot do a video which would make it very clear whats going on.
Sounds like you have an intermittent supply of 3V and 15V to the sockets. Could be a poor contact on the switch or a broken trace on the board. Can you connect a voltmeter to the probes and see if the voltage drops when you wiggle?
 

Offline lowimpedance

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Re: EEVblog 121GW Multimeter Issues
« Reply #114 on: January 18, 2018, 04:54:57 pm »
Okay checking the output with a voltmeter still gives 3 or 15V when continuous beep is going, also when this condition has started the display also goes to all '0' from OFL so no short at the input terminals it would seem.

Just tried a short drop of a few inches height to my desk (no probes) and that can also trigger the continuous beep. This is with no holster BTW.

When the Diode function is not doing the odd behaviour it does measure a diode correctly.

edit: The drop test is not as repeatable as the movement of the probes in the input jacks. I still get the feeling its related to the switch. 
 I will crack it open and take a look tomorrow  to see what movement on the PCB can be induced from the probe jacks.
« Last Edit: January 18, 2018, 05:03:28 pm by lowimpedance »
You call that current ?.......
I'll show you current !
 the odd multimeter or 2 or 3 or 4...or........never mind
 

Offline amspire

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Re: EEVblog 121GW Multimeter Issues
« Reply #115 on: January 18, 2018, 05:12:48 pm »
Okay checking the output with a voltmeter still gives 3 or 15V when continuous beep is going, also when this condition has started the display also goes to all '0' from OFL so no short at the input terminals it would seem.
So it looks like the intermittent connection is somewhere between the measurement IC and the point at which the 3/15v is connected. I still think a switch connection is the most likely cause. You probably should contact Dave directly, unless you want to just Take-It-Apart yourself and have a look.
 

Offline maukka

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Re: EEVblog 121GW Multimeter Issues
« Reply #116 on: January 18, 2018, 06:32:48 pm »
This was already reported by mattselectronics in the other thread, but the VA mode reports voltage wrong. On 5V range it is too high, on 50V range is much better but a bit too low. Gets worse with higher voltages. Tested with a resistor and a Rigol DP811A with remote sense active. No problems when only measuring voltage, only max 1 digit off. Current is spot on.







EDIT: Did the same test with a Mooshimeter which also has VA (and real power) measurement and it is even more off

Actual measured with a 34401A from DMM terminals: 1.0008V
112GW 1.0133V
Mooshimeter 1.02022V

The Mooshimeter shows 2.0% more than it should, but it is consistent regardless of voltage while on the 112GW error gets larger with increasing voltage.


« Last Edit: January 18, 2018, 09:29:30 pm by maukka »
 
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Offline maukka

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Re: EEVblog 121GW Multimeter Issues
« Reply #117 on: January 19, 2018, 12:51:46 am »
How much burden voltage do you guys have on the 10A range? Mine is 0.035V/A measured externally while the manual says 0.02V/A. The 112GW itself reports 28.7mV/A.

« Last Edit: January 19, 2018, 01:00:23 am by maukka »
 

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Re: EEVblog 121GW Multimeter Issues
« Reply #118 on: January 19, 2018, 10:08:15 am »
How much burden voltage do you guys have on the 10A range? Mine is 0.035V/A measured externally while the manual says 0.02V/A. The 112GW itself reports 28.7mV/A.

Latest edition of the manual has this revised to 0.03V/A, will upload this when I get back tomorrow.
The previous one didn't include the fuse resistance.
 
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Offline cpposteve

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Re: EEVblog 121GW Multimeter Issues
« Reply #119 on: January 19, 2018, 10:25:18 am »
Hello mr Jones..!!
Just curious as to when people will get their answers to these on going faults? I’m in the second batch of meters not yet shipped and wondering if all these faults will or most likely be able to be fixed in software?
Hope you had a great holiday.

Steve
 

Offline lowimpedance

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Re: EEVblog 121GW Multimeter Issues
« Reply #120 on: January 19, 2018, 12:58:51 pm »
 I created a Youtube acc. and uploaded a very short video clip of the Diode test mode continuous beep after giving the probe plugs a wiggle in the meter sockets.
I then removed the probes from the meter to show no external short circuits being the cause and then how a light press on the range switch will stop the tone.



I hope this clarifies my earlier posts.

(I will open the meter to investigate this after a weeks holiday)
You call that current ?.......
I'll show you current !
 the odd multimeter or 2 or 3 or 4...or........never mind
 
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Offline Iagash

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Re: EEVblog 121GW Multimeter Issues
« Reply #121 on: January 19, 2018, 01:33:54 pm »
I created a Youtube acc. and uploaded a very short video clip of the Diode test mode continuous beep after giving the probe plugs a wiggle in the meter sockets.
I then removed the probes from the meter to show no external short circuits being the cause and then how a light press on the range switch will stop the tone.
(I will open the meter to investigate this after a weeks holiday)

I can confirm this. I also experienced the switch to be unreliable some times.

I fixed it by mounting two small sheets of 0.25mm telson below the snap ring of the switch.

I'll attach a photo.
 
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Offline 1anX

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Re: EEVblog 121GW Multimeter Issues
« Reply #122 on: January 19, 2018, 03:24:07 pm »
I created a Youtube acc. and uploaded a very short video clip of the Diode test mode continuous beep after giving the probe plugs a wiggle in the meter sockets.
I then removed the probes from the meter to show no external short circuits being the cause and then how a light press on the range switch will stop the tone.
(I will open the meter to investigate this after a weeks holiday)

I can confirm this. I also experienced the switch to be unreliable some times.

I fixed it by mounting two small sheets of 0.25mm telson below the snap ring of the switch.

I'll attach a photo.

Hmmm, looks like it requires some form of spring/wave washer type tension device included. Case may not be rigid enough to provide consistent tension for the contacts without a simple spring tension device being fitted!

Wave washer info here http://www.globalspec.com/learnmore/mechanical_components/springs/wave_washers

That's not a good indicator for the construction robustness of the meter and hopefully a simple mechanical fix will be found. Well documented and fixed Iagash, we all benefit from your faulty switch investigation.
« Last Edit: January 19, 2018, 07:39:53 pm by 1anX »
 

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Re: EEVblog 121GW Multimeter Issues
« Reply #123 on: January 19, 2018, 07:53:46 pm »
I can confirm this. I also experienced the switch to be unreliable some times.
I fixed it by mounting two small sheets of 0.25mm telson below the snap ring of the switch.
I'll attach a photo.

I do not understand this.
That fix is on the case of the meter, not on the carrier that holds the switch contacts which is a different assembly mounted and clipped to the PCB that has it's own tension with the plastic insert clip.
 

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Re: EEVblog 121GW Multimeter Issues
« Reply #124 on: January 19, 2018, 07:54:23 pm »
Hello mr Jones..!!
Just curious as to when people will get their answers to these on going faults?

When I know, you'll know.
 
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Offline Iagash

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Re: EEVblog 121GW Multimeter Issues
« Reply #125 on: January 20, 2018, 12:44:44 am »
I can confirm this. I also experienced the switch to be unreliable some times.
I fixed it by mounting two small sheets of 0.25mm telson below the snap ring of the switch.
I'll attach a photo.

I do not understand this.
That fix is on the case of the meter, not on the carrier that holds the switch contacts which is a different assembly mounted and clipped to the PCB that has it's own tension with the plastic insert clip.

Yes, but the effect is the same. The range switch is pressed a little more to the pcb by the clip ring. With this washer the plastic insert clip is relieved. It seemed easier that way as you can see in the video poking the range switch makes the meter switch the mode. When poking the range switch from the top, you also apply pressure via the clip ring to the switch and move it a bit more to the pcb.

Edit:
Since there are only very little reports here about the switch, it might be a tolerance issue which only affects a minority of meters.
« Last Edit: January 20, 2018, 12:54:31 am by Iagash »
 

Offline amspire

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Re: EEVblog 121GW Multimeter Issues
« Reply #126 on: January 20, 2018, 03:41:11 am »
I think the switch problem may be due to two things:
  • The fact the selector knob wobbles much more then other multimeters I have seen - even the $10 ones
  • If you push the knob down, the clip ring pushes down on the switch. Not sure that should happen

The wobble in the knob is wobbling the switch on the PCB from side to side. Probably not good if you want to maintain the tension in the spring contacts in the switch.

The looseness of the clip spring combined with the tapers of both the knob and the case knob recess all combine to allow for this wobble. If the knob was moulded with a reverse taper so it is wider at the top then the bottom, it could have a far more snug fit and would be less affected by any clip ring looseness.

As an experiment, I added a spacer between the knob and the nylon detent spring to raise the knob so that the clip ring groove was just above the inner case plastic, but the clip ring was not tight against the plastic. This is different from the approach Iagash took. I also added a couple of layers of Kapton tape around the outside of the knob to stop the wobble a little. It now seems that pressing on the knob never depresses the switch, and the wobble is much less. I think the switch has a better feel now.

Basically what I am saying is if the knob moulding was tweaked a bit, the switch could possible be more reliable and feel much more solid. It is just out here and there by fractions of a millimetre and that is all it takes.

Don't know what the best advice is for people with contact issues. I would probably want to inspect the contacts to see if any had been deformed a little. You should not need to have the clip ring pushing the switch down by perhaps 0.1mm. That does not feel like a real solution.
« Last Edit: January 20, 2018, 09:34:53 am by amspire »
 

Offline lowimpedance

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Re: EEVblog 121GW Multimeter Issues
« Reply #127 on: January 20, 2018, 09:02:31 am »
I should emphasize that the diode tone issue I have starts from the probe movement
In their sockets and not from switch movement. But once started both probe and gentle
pressure on the switch will stop it, as shown in the short video.
BTW it was too hard to video and show wiggled that probes (mobile phone in one hand).
You call that current ?.......
I'll show you current !
 the odd multimeter or 2 or 3 or 4...or........never mind
 

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Re: EEVblog 121GW Multimeter Issues
« Reply #128 on: January 20, 2018, 10:11:33 am »
Basically what I am saying is if the knob moulding was tweaked a bit, the switch could possible be more reliable and feel much more solid. It is just out here and there by fractions of a millimetre and that is all it takes.

Switch wobble confirmed on the two remaining meters we have here.
We (as in David2 + me) also suspect it's some slight difference in production tooling process, although the pre-production was obviously supposed to be the same.
The pre-production units were fine.

REMINDER, please keep discussions in the discussion thread:
http://www.eevblog.com/forum/testgear/eevblog-121gw-discussion-thread/
 
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Offline 3db

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Re: EEVblog 121GW Multimeter Issues
« Reply #129 on: January 20, 2018, 08:58:39 pm »
IIRC the point of not open-sourcing it is that messing with the firmware could affect the safety of the meter so there's no way they can officially sanction that or help people to do it.

Dave maybe can sell a version with open source firmware as DMM development kit? As a dev kit, you can basically bypass any certification requirements.

There is absolutely nothing stopping anyone writing their own firmware and making it open source.

Does that include YOU Dave ?
 

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Re: EEVblog 121GW Multimeter Issues
« Reply #130 on: January 20, 2018, 09:16:31 pm »
There is absolutely nothing stopping anyone writing their own firmware and making it open source.
Does that include YOU Dave ?

No, the ridiculous amount of time spent on the open source app taught us not to touch the firmware.
 

Offline ChrisG

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Re: EEVblog 121GW Multimeter Issues
« Reply #131 on: January 20, 2018, 09:46:14 pm »
Confirmed issues (or annoyances) from what I've (re)-tested so far.

1. Slow auto-ranging: Ohms, Voltage, Capacitance
2. double double double beeps constantly going on when in diode mode
3. measuring any resistance (short or higher value) in diode mode gives a constant and loud beep
4. Wobbly selector/range switch: back an forth (vertical) when in diode mode it will even blink the back-light or completely switch off.
5. Strange to me is that when in diode mode a small green LED has a Vf of 1.79 in the 3V mode and a Vf of 1.98 in the 15V mode. And also is a bit brighter then.

Hope this helps,

6. on the lower current fuse is rated 600V and 400mA from ASTM. Which is different from the manual: 440mA and 1000V. I believe this was somewhere posted already?
« Last Edit: January 22, 2018, 01:17:08 am by ChrisG »
 

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Re: EEVblog 121GW Multimeter Issues
« Reply #132 on: January 20, 2018, 10:18:44 pm »
3. measuring any resistance (short or higher value) in diode mode gives a constant and loud beep

That feature was requested by people.

Quote
5. Strange to me is that when in diode mode a small green LED has a Vf of 1.79 in the 3V mode and a Vf of 1.98 in the 15V mode. And also is a bit brighter then.

Expected, as they result in different test currents.
 
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Offline amspire

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Re: EEVblog 121GW Multimeter Issues
« Reply #133 on: January 20, 2018, 10:25:23 pm »
Manual Correction Dec 11:

The manual specifications is a bit vague on diode test currents. It mentions 1.4mA and 7mA short circuit but they don't really line up with the 3V range and 15V ranges.

It seems the actual currents are different on my meter (v1.01):

3V    0.7mA short circuit
15V  4.6mA

Page 44 mentions the Diode Test current is limited by a resistor + PTC totalling about 2.2K. Has this changed?

ChrisG: Your point 5 is not an issue - the two diode tests are at two different currents. The voltages are meant to be different.
« Last Edit: January 20, 2018, 10:33:21 pm by amspire »
 
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Offline Fungus

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Re: EEVblog 121GW Multimeter Issues
« Reply #134 on: January 21, 2018, 12:38:01 am »
The manual specifications is a bit vague on diode test currents. It mentions 1.4mA and 7mA short circuit but they don't really line up with the 3V range and 15V ranges.

It seems the actual currents are different on my meter (v1.01):

3V    0.7mA short circuit
15V  4.6mA

Short circuit current is a maximum. It will be less when there's no short circuit.
 

Offline amspire

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Re: EEVblog 121GW Multimeter Issues
« Reply #135 on: January 21, 2018, 02:12:29 am »
The manual specifications is a bit vague on diode test currents. It mentions 1.4mA and 7mA short circuit but they don't really line up with the 3V range and 15V ranges.

It seems the actual currents are different on my meter (v1.01):

3V    0.7mA short circuit
15V  4.6mA

Short circuit current is a maximum. It will be less when there's no short circuit.

Huh?  I am just mentioning a case where the specifications for short circuit current and the actual meter are different. Also the formatting of the specifications does not have values lining up correctly. It may be the resistor in the final meter are different from the prototype meter. That is all. Dave has mentioned that he wants to soon release an updated version of the manual. It is part of the product.
« Last Edit: January 21, 2018, 02:15:20 am by amspire »
 

Offline mikeselectricstuff

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Re: EEVblog 121GW Multimeter Issues
« Reply #136 on: January 21, 2018, 02:34:04 am »
I wouldn't expect a low to mid-DMM diode check function to have particularly constant current.
Some quick checks on my meters over the reading range :
Fluke 87 (i and III) 0.8 to 0.15mA
Fluke 287 1mA up to 2V, then down to 0.8mA at 3v
Agilent 36641A 1mA constant
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Offline amspire

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Re: EEVblog 121GW Multimeter Issues
« Reply #137 on: January 21, 2018, 03:25:48 am »
No one is suggesting constant current. I have done a report on short circuit currents of my meter because they are different from the spec. It would be useful if you can confirm my numbers, or if your 121GW meter matches the spec.
« Last Edit: January 21, 2018, 11:17:11 am by amspire »
 

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Re: EEVblog 121GW Multimeter Issues
« Reply #138 on: January 21, 2018, 11:16:06 am »
No one is suggesting constant current. I have done a report on short circuit currents of my meter because they are different from the spec. It would be useful if you can confirm my numbers, or if your 121GW meter matches the spec. O miss
0.7mA on 3V range
4.25mA on 15V range
 
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Offline ChrisG

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Re: EEVblog 121GW Multimeter Issues
« Reply #139 on: January 22, 2018, 12:39:50 am »
No one is suggesting constant current. I have done a report on short circuit currents of my meter because they are different from the spec. It would be useful if you can confirm my numbers, or if your 121GW meter matches the spec. O miss
0.7mA on 3V range
4.25mA on 15V range
0.71 mA on 3V range
4.61 mA on 15V range

Measured through a BM869s.
 

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Re: EEVblog 121GW Multimeter Issues
« Reply #140 on: January 22, 2018, 02:48:27 pm »
UPDATE:
UEi are aware of the various issues and are working on them.
The autoranging as you might expect is not necessarily trivial and will take a few more days to test this.
For the range switch they are waiting on a slightly modified part to see if that can solve it.
 

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Re: EEVblog 121GW Multimeter Issues
« Reply #141 on: January 22, 2018, 03:14:45 pm »
If UEi are fixing the Autoranging, it might be a good opportunity to fix the non-working DC mVA/VA autoranging with negative currents.
 

Offline borealis

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Re: EEVblog 121GW Multimeter Issues
« Reply #142 on: January 23, 2018, 01:50:08 am »
Hi Dave

On my meter pins PE13 (SPI1_SCK/FSMC_D10) and PE14 (SPI_MISO/FSMC_D11) of the STM32L1 are shorted together (continuity tested). The attached file has the best focused image I could get of this. Should I do anything about it?
 

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Re: EEVblog 121GW Multimeter Issues
« Reply #143 on: January 24, 2018, 08:57:44 am »
Metal parts in range switch will make it more enjoyable to use...
 

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Re: EEVblog 121GW Multimeter Issues
« Reply #144 on: January 24, 2018, 09:39:06 am »
On my meter pins PE13 (SPI1_SCK/FSMC_D10) and PE14 (SPI_MISO/FSMC_D11) of the STM32L1 are shorted together (continuity tested). The attached file has the best focused image I could get of this. Should I do anything about it?

That's VSSA and VREF-, they should be connected.
Looks like they used a direct track in-between pins which trapped the solder.
Nothing to worry about.
 

Offline benst

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Re: EEVblog 121GW Multimeter Issues
« Reply #145 on: January 24, 2018, 10:51:59 am »
The switch on my meter (#000499) is also wobbly and has the problem described here.

I took it apart, and contacts and pcb looked ok. After I put it back together it worked allright for a while, but now it's back and I have to fiddle with the switch again to get it to display correct readings. :-BROKE

Dave, once UEi figures out a fix, will you send out a replacement part?

Thanks,
Ben
I hack for work and pleasure.
 

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Re: EEVblog 121GW Multimeter Issues
« Reply #146 on: January 24, 2018, 11:06:08 am »
The switch on my meter (#000499) is also wobbly and has the problem described here.
I took it apart, and contacts and pcb looked ok. After I put it back together it worked allright for a while, but now it's back and I have to fiddle with the switch again to get it to display correct readings. :-BROKE
Dave, once UEi figures out a fix, will you send out a replacement part?

Yes we'll have to do that for those existing shipments who have problems.
 
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Online dr.diesel

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Re: EEVblog 121GW Multimeter Issues
« Reply #147 on: January 24, 2018, 11:38:35 am »
Minor Issue:

I just opened my 2nd set of leads, note the positive lead, recessed threaded portion, and it's broken internally.  Slightly flexing the break in the 2nd photo to accentuate the area.

It's electrically connected however.  (Replacements not necessary, I got a zillion of them)


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Re: EEVblog 121GW Multimeter Issues
« Reply #148 on: January 24, 2018, 11:59:14 am »
Minor Issue:

I just opened my 2nd set of leads, note the positive lead, recessed threaded portion, and it's broken internally.  Slightly flexing the break in the 2nd photo to accentuate the area.

It's electrically connected however.  (Replacements not necessary, I got a zillion of them)

It happens in large numbers. My BM235 with the same probes has done that the inside spins on when I screw on the banana jacks. So I’ve just been carful to not torque that one since I fear the wire might eventually twist to much and break off. I even had one probe new with the fluke 289 that was bent, they did replace that one since they reached out to me. I guess they saw it on the unboxing video.
I never bothered to mention it since I have the probematers and a few fluke probes. Like you, I have enough of them, but sometimes I have to run three meters and I usually use the probes they came with.

That brings up a good question, I know Brymen is responsive to fixing and communicating with customers to fix issues. So if the probes have an issue, who do we contact since Brymen makes the probes but UEI made the meter? Do we contact UEI, Brymen, or EEVBlog (Dave)?

Please be sure to check out my YouTube channel and subscribe if you like the videos. http://www.youtube.com/c/GadgetReviewVideos

By people subscribing and giving thumbs up I know what I am doing is still wanted and adding value, then will continue to release new videos. Thank you for your support.
 

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Re: EEVblog 121GW Multimeter Issues
« Reply #149 on: January 24, 2018, 12:04:30 pm »
inside spins

This one is tight, perhaps just in the wrong position when molded.

I suspect the wire lead is terminated at the break in my case above, which means it probably wouldn't last long in the field.

Offline Kean

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Re: EEVblog 121GW Multimeter Issues
« Reply #150 on: January 25, 2018, 02:38:52 am »
Just confirming an issue reported by Joe Smith on the prototype unit he tested still exists on my production unit.
As posted in the discussion thread at http://www.eevblog.com/forum/testgear/eevblog-121gw-discussion-thread/msg1408767/#msg1408767
And confirmed by maukka in a followup post http://www.eevblog.com/forum/testgear/eevblog-121gw-discussion-thread/msg1408768/#msg1408768

I wonder if someone could check the meter in the LowZ mode.   In the early unit, if I applied a 1VRMS 60Hz signal, the meter would read zero as expected.   However, when I would increase the frequency to 389KHz, the meter was displaying 181.3 volts even though there was still only a volt being supplied.   There was something strange going on with it that I never looked into.  I reported the problem when I discovered it but with as many problems that the meter still has, I wonder if this was addressed in the released version.

Joe, I can confirm this issue is still present in FW1.01.
I generated a 2.8Vpp 60Hz (& 1kHz) sine wave with my MSO1104Z-S and it read 0V in LowZ mode.
When I upped the freq to 389kHZ and I got a reading of 189.2Vac.  See photo...

Edit: and it correctly read ~1V AC without LowZ up to maybe 100kHz, but that dropped to 0.773V AC at 389kHz
 

Offline ChrisG

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Re: EEVblog 121GW Multimeter Issues
« Reply #151 on: January 25, 2018, 04:04:21 am »
Confirmed... Though it does too vary a bit when changing frequencies.

 

Offline tpw_rules

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Re: EEVblog 121GW Multimeter Issues
« Reply #152 on: January 25, 2018, 09:19:27 am »
Does this LowZ issue happen in the ACV's highest (600V) range? The two are calculated virtually identically in the software. If there's an issue with the routines or calibration data for that ACV mode, they should be broken in the same way. Of course, I'm not saying that them not behaving the same means it has to be fixed in hardware.

Edit: the calibration tables are also only specified up to 10KHz. Perhaps the 10KHz correction factor becomes invalid at such a high frequency? Can anyone dump their calibration data (requires firmware 1.02) for me?
« Last Edit: January 25, 2018, 09:37:56 am by tpw_rules »
 

Offline Iagash

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Re: EEVblog 121GW Multimeter Issues
« Reply #153 on: January 25, 2018, 10:32:19 am »
Edit: the calibration tables are also only specified up to 10KHz. Perhaps the 10KHz correction factor becomes invalid at such a high frequency? Can anyone dump their calibration data (requires firmware 1.02) for me?

Here you go, I attach it zipped.
 

Offline tpw_rules

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Re: EEVblog 121GW Multimeter Issues
« Reply #154 on: January 25, 2018, 03:16:14 pm »
So I toyed around in Python and got some interesting results. There is a routine which takes the measured input frequency and value, then calculates an offset based on these two factors. It is possible for a large negative calibration value to produce the behavior, but the required value seems kind of crazy (though the firmware would accept it as valid). See here for a graph of that result.

Some other notes:
  • The number in question is a signed 2 byte big endian number located at 0x68 in CAL.BIN. The copy that I have has 26. Does anyone's have a very large negative number? The one at 0x6A is relevant as well, my calibration copy has 217.
  • Low-Z mode has a hysteresis effect: it won't move off 0V until it believes the input is above 10V (incl. as a result of above calibration shenanigans) and will drop back to 0V if the input drops below 3V.
  • But, the ACV mode switched to 600V range is identical in almost every respect to Low-Z in AC mode, software-wise. Can you duplicate the problem in ACV on the 600V range? I assume Kean's test probably used the 5V range. It should also give you a better picture at what's happening at lower frequencies when the believed input is <10V. ACV can also display the believed input frequency by pressing 'SETUP' enough times.
« Last Edit: January 25, 2018, 03:21:00 pm by tpw_rules »
 

Offline ChrisG

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Re: EEVblog 121GW Multimeter Issues
« Reply #155 on: January 25, 2018, 07:26:44 pm »
I re-tested in my early morning and in the LowZ position I could not change the range and it indicated 1000v in the lower right hand corner. So assume yes this is the highest 600V then too. Upping the Vpp to 5.0v at 389Khz the result was a staggering 367v on the display.
 

Offline Kean

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Re: EEVblog 121GW Multimeter Issues
« Reply #156 on: January 26, 2018, 01:35:01 am »
@ChrisG What tpw_rules was suggesting I believe was to input the 1Vrms 100+kHz input into the VAC mode (instead of LowZ), and then manually select 1000V range.  And thus see if the same wrong readings were displayed as in LowZ.

Well I just did that, and got some interesting - but not consistent - results.

With 2.8Vpp (~1Vrms) sine at 300kHz:
LowZ AV 1000V range read 161V - consistent
VAC auto range (5V)  read 1.63V 299.9kHz - once only, see below - otherwise ~1V 299.9kHz
VAC 5V range read 1.63V 299.9kHz - once only, see below - otherwise ~1V 299.9kHz
VAC 50V range read 12.6V 299.8kHz - once only, see below - otherwise 0V 0Hz
VAC 500V range read 149.2V 299.8kHz - once only, see below - otherwise 0V 0Hz
VAC 1000V range read 149.3V 299.8kHz - once only, see below - otherwise 0V 0Hz

I actually tried going through these VAC ranges (and back and forth to LowZ) several times.  The first time gave the 0V 0Hz on the AC 50V ranges and above (can't recall the 5V range reading).  The second time the above high readings.  And all subsequent times back to the 1V or 0V.

Then tried 1kHz and 10kHz inputs, and got slightly low readings in the higher ranges (1V in 5V range dropping down to 0.6-0.7V in 1000V range), but also interesting was that it couldn't display the frequency any more in the 50V and higher ranges.  It then just showed 0Hz.  The meter is specified to 5kHz in the VAC mode, but I guess in those manual ranges the attenuation is too high for the frequency measurement.  But how does it "work" then in LowZ mode (i.e. measures correct frequency, but incorrect voltage) if also using the 1000V range attenuation?

I tried several things including increasing my output to 5Vpp and I couldn't get those strange readings again.  The fact it happened once does point to tpw_rules theory about the whacky adjustment for frequency being potentially correct.  Or I could have been hit with the rotary switch wobble issue that one time.  Or maybe there is a specific sequence needed to reproduce...   |O

While doing this I noticed another strange reading on AC mV manual ranges too.  Same 2.8Vpp 300kHz sine wave.  On 50mV range it read 23.0mV, and on 500mV range OFL.   :-//  At 10kHz both showed OFL.  Limited bandwidth coming to play here I guess - way beyond the 5kHz spec, and not as worrying as the weird LowZ readings.
 

Offline exe

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Re: EEVblog 121GW Multimeter Issues
« Reply #157 on: January 26, 2018, 05:31:35 am »
If the switch is wobbly, but the measurements are not affected by moving it, is this still a defect?
 

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Re: EEVblog 121GW Multimeter Issues
« Reply #158 on: January 26, 2018, 05:37:55 am »
If the switch is wobbly, but the measurements are not affected by moving it, is this still a defect?

I'd argue the wobbly switch has a questionable longevity. 

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Re: EEVblog 121GW Multimeter Issues
« Reply #159 on: January 26, 2018, 08:37:48 am »
I'd argue the wobbly switch has a questionable longevity.

Possibly, but it could be by design. There should be some slack between the switch knob on the case and the switch mechanism on the PCB, so that rotating the switch does not put excessive stress on the PCB.
I'm not an EE--what am I doing here?
 

Offline tpw_rules

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Re: EEVblog 121GW Multimeter Issues
« Reply #160 on: January 26, 2018, 08:54:11 am »
@ChrisG What tpw_rules was suggesting I believe was to input the 1Vrms 100+kHz input into the VAC mode (instead of LowZ), and then manually select 1000V range.  And thus see if the same wrong readings were displayed as in LowZ.

...

I tried several things including increasing my output to 5Vpp and I couldn't get those strange readings again.  The fact it happened once does point to tpw_rules theory about the whacky adjustment for frequency being potentially correct.  Or I could have been hit with the rotary switch wobble issue that one time.  Or maybe there is a specific sequence needed to reproduce...   |O

You are correct about what I intended. I've been calling it the 600V range because that's what it's referred to in the calibration chart.

As for the behavior, ...huh. I'm not sure what to make of that, if it proves or disproves my theory. I've made another patch which removes the software frequency compensation entirely. If you can't replicate the behavior in any mode, that compensation must be the problem. If this is what happens, can you dump your calibration data using the patched firmware and upload it for me? I don't know much about the meter circuit, so someone else will have to take over if that doesn't fix it. It may end up being fixable in software though.
 

Offline Candid

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Re: EEVblog 121GW Multimeter Issues
« Reply #161 on: January 28, 2018, 03:57:04 am »
With the patched no frequency compensation 1.02 version I have identical behavior as with the 1.02 (autorange patched) version and as described by Kean.

And for the frequency thing:
At about 15Vpp/1kHz I can switch between 5V and 50V range without OFL in 5V range. Then I get correct Hz reading on both ranges. Going to 500V and 1000V range voltage reading stays ok but Hz again is 0.
« Last Edit: January 28, 2018, 04:26:32 am by Candid »
 

Offline ChrisG

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Re: EEVblog 121GW Multimeter Issues
« Reply #162 on: January 28, 2018, 05:14:29 am »
you patched the firmware or which patch did you apply? If you're still in version 1.02 of the firmware what would be different then?
 

Offline Candid

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Re: EEVblog 121GW Multimeter Issues
« Reply #163 on: January 28, 2018, 07:01:37 am »
I tested the tpw_rules 1.02 with removed frequency compensation (see one post above my last one).
 

Offline ChrisG

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Re: EEVblog 121GW Multimeter Issues
« Reply #164 on: January 28, 2018, 11:13:00 pm »
you patched the firmware or which patch did you apply? If you're still in version 1.02 of the firmware what would be different then?

Apologies, I now see the download firmware link..  :-//
 

Online EEVblog

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Re: EEVblog 121GW Multimeter Issues
« Reply #165 on: January 31, 2018, 12:28:53 pm »
With 2.8Vpp (~1Vrms) sine at 300kHz:
LowZ AV 1000V range read 161V - consistent
VAC auto range (5V)  read 1.63V 299.9kHz - once only, see below - otherwise ~1V 299.9kHz
VAC 5V range read 1.63V 299.9kHz - once only, see below - otherwise ~1V 299.9kHz
VAC 50V range read 12.6V 299.8kHz - once only, see below - otherwise 0V 0Hz
VAC 500V range read 149.2V 299.8kHz - once only, see below - otherwise 0V 0Hz
VAC 1000V range read 149.3V 299.8kHz - once only, see below - otherwise 0V 0Hz


I don't understand why you are testing at 300KHz? That's way outside the frequency spec.
 

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Re: EEVblog 121GW Multimeter Issues
« Reply #166 on: January 31, 2018, 01:30:22 pm »
The Low-Z reading problem at high frequencies is confirmed and has been reported.
 
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Offline ChrisG

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Re: EEVblog 121GW Multimeter Issues
« Reply #167 on: February 02, 2018, 01:10:39 am »
all, has it been pointed out here on this list the duty cycle:


  • on an a-symmetrical square waveform is displayed inverse on the 121GW? I noticed that yesterday evening and re-tested it 10 times. so 40% on the SDG2042x is displayed as 60% on the 121GW, 70% duty cycle is then 30% on the 121GW and so on.
  • It needs 1 Vpp or more to actively announce the duty cycle. 500mVpp or below nothing happens. 600mVpp or more I might be lucky.
  • where the % sign is oddly placed next to the Temperature.... AARHHHHHGGG).
 

Offline amspire

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Re: EEVblog 121GW Multimeter Issues
« Reply #168 on: February 02, 2018, 03:50:51 pm »
121GW Manual revision 24 Jan 2018 (minor issue):
http://www.eevblog.com/files/EEVblog-121GW-Manual.pdf

On page 57, the description of the Setup Option Multimeter ID has been added, but it was not added to the list on page 53.
The correct order should be:
Quote
1. Temperature
2. Battery Voltage
3. Auto Power Off (APo)
4. LCD Contrast
5. Year
6. Month-Day
7. Hour-Minute
8. Multimeter ID
9. Logging Interval (ln 1)
10. Additional settings dependent upon the function selected.
 

Offline Candid

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Re: EEVblog 121GW Multimeter Issues
« Reply #169 on: February 08, 2018, 07:20:43 pm »
I made some measurements with my FeelTech FY6600 and RD JDS6600 function generators concerning the phantom voltage to earth. Both of them use simple SMPS and I can measure about 80Vac to earth in normal mode.

In LowZ mode I would expect only some Vac. I checked with my Brymen 235 and the 121GW. Both behave like expected but with the 121GW, when I wait some seconds suddenly it measures about 70Vac in LowZ mode but only with the FeelTech FY6600 not with the RD JDS6600?

The Brymen 235 (and a labeled UNI-T the Voltcraft VC890 from Conrad Electronic in Germany) always give me the correct(?) LowZ behavior.

Can someone confirm this and does anybody know why the 121GW behaves like this?
 

Offline HKJ

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Re: EEVblog 121GW Multimeter Issues
« Reply #170 on: February 08, 2018, 07:41:01 pm »
LowZ is often a PTC that draws current, depending on the current it will heat up and increase resistance. It sounds like the PTC in the 121GW heats up faster or at lower current.
 

Offline amspire

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Re: EEVblog 121GW Multimeter Issues
« Reply #171 on: February 09, 2018, 11:32:56 pm »
Capacitance in Manual Ranging not properly detecting Overflow
121GW Ver 1.01

In Auto Ranging mode, if you attach a 100uF electrolytic capacitor, the meter steps through the ranges to the correct range in less than 5 seconds, so the meter can detect the OFL state on a range fairly quickly.

However in manual ranging modes, if you step through the ranges with the same 100uF electrolytic capacitor attached, the period can be 10s of seconds to show OFL to never showing OFL in the low ranges.

It seems the oscillator measuring the capacitance has no timeout, and so it will happily wait forever for the capacitor to charge. With electrolytic leakage, it may never reach a voltage on the lowest ranges to complete a single reading. There is no sense in this in that in all ranges, there is a maximum possible time for a reading, and so there is no reason not to time out the reading and show OFL.

While you are waiting, the meter shows the last successful reading - usually zero.

For the same reason, if you short the leads in capacitance mode with manual ranging, the meter just shows the last reading forever. Usually zero.

In autoranging, a short will cause the display to blank and it will autorange to the maximum range, but it may be that it has no timeout in this maximum range either. At least the display is blank rather then zero.

The problem with this is that you cannot tell whether you are reading something that has no capacitance or something that has a lot of capacitance when in a manual range. I would expect to see OFL if the capacitance is too big for a manual range.
« Last Edit: February 09, 2018, 11:48:20 pm by amspire »
 

Offline ChrisG

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Re: EEVblog 121GW Multimeter Issues
« Reply #172 on: February 20, 2018, 07:27:34 pm »
Hello all, it's been quite the time there has been a post here, 11 days. I'm just wondering if there isnow an overall issue or backlog list. HW and SW related. I assume there must be and is Dave able to share it then here?
 
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Offline bitwelder

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Re: EEVblog 121GW Multimeter Issues
« Reply #173 on: March 05, 2018, 02:23:23 am »
I hope this thread would work also for issues regarding the documentation.

Regarding the manual (revision 24.1.2018), I would suggest:
- add a reference to the meter f/w version, not only the manual revision date (e.g. setup menu has a paragraph about buzzer on/off, but that option doesn't exist in fw v1.01)
- the Auto Power Off function is mentioned, but it doesn't describe after how many minutes it triggers.
 

Offline lowimpedance

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Re: EEVblog 121GW Multimeter Issues
« Reply #174 on: March 08, 2018, 01:23:14 pm »
 In diode test mode the temperature display still remains on instead of showing the currently set test voltage. Pressing the RANGE button will toggle to the test voltages,  but switch to another function then back to diode test and the test voltage is replaced with temperature again.
 Also when the beeper is disabled and you select the continuity mode the beeper symbol on the LCD is on but the beep is off. As others have noted in the discussion thread the beep mode should have multiple options for the functions that actually need the beep.
You call that current ?.......
I'll show you current !
 the odd multimeter or 2 or 3 or 4...or........never mind
 

Offline lowimpedance

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Re: EEVblog 121GW Multimeter Issues
« Reply #175 on: March 08, 2018, 01:25:48 pm »
Minor manual correction, the 500mA text on the front cover picture is still missing next to the A text over the current input jack.
You call that current ?.......
I'll show you current !
 the odd multimeter or 2 or 3 or 4...or........never mind
 

Offline lowimpedance

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Re: EEVblog 121GW Multimeter Issues
« Reply #176 on: March 14, 2018, 11:39:37 am »
 When in Ohms (auto range) mode and shorting the probes the display will show some random numbers for a short time before ranging down to display the value of the shorted probes.
So 95 % of the time the random numbers come up instead of blanking the display while changing ranges. It only occurs on the top M Ohm range and will blank as soon as the auto ranging starts.
Do others see this effect on theirs with firmware version 1.07. ?.
Not a major issue, but hopefully will be corrected at some point.
You call that current ?.......
I'll show you current !
 the odd multimeter or 2 or 3 or 4...or........never mind
 

Offline morrone

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Re: EEVblog 121GW Multimeter Issues
« Reply #177 on: March 17, 2018, 04:09:42 am »
So 95 % of the time the random numbers come up instead of blanking the display while changing ranges. It only occurs on the top M Ohm range and will blank as soon as the auto ranging starts.
Do others see this effect on theirs with firmware version 1.07. ?.

Yes, I see the same thing with 1.07.  When the probes are applied to a resistor the screen blanks for a moment, then shows a random bad value and pauses for a second or two with no sign that it is still working to find the correct value, then it blanks again briefly before showing the correct value with relatively rapid updates to the lest significant digits.
 

Online bicycleguy

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Re: EEVblog 121GW Multimeter Issues
« Reply #178 on: March 30, 2018, 03:41:51 am »
minor Manual, 07 March 2018,

Page  kind  description
7  spelling 'VERION'
29 grammar (twice), 'for the is jack'
59 grammar, 'and is can be'

Starting to look pretty good !
 

Offline Candid

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Re: EEVblog 121GW Multimeter Issues
« Reply #179 on: April 07, 2018, 09:33:02 pm »
I already posted in the discussion thread about a problem I have with Vac readings. Now I will switch to the correct place for this.

In 5Vac mode I get wrong readings.

Today I checked the ZERO OFFSET CALIBRATION and had to find out, that only in 5Vac range mode with shorted inputs I get a reading of 0,499xVac. With open input I get nearly the same value of about 0,5Vac.

In all other Vac (and Vdc) ranges I get 0,0xxV. So I tried to calibrate only the zero offset in Vac 5V range mode. During the count down it displays the 0,499xV and after the calibration I still have this offset with shorted inputs on the 5Vac range. At the end of the calibration countdown I see "OFF-E" for about half a second what is not mentioned in the manual.

I have two references from voltagestandard.com. The 121GW is spot on for all voltage measurements I can do (Vdc 0,350V up to 10.000V and Vac 5V).

So there must be something wrong with the 5Vac range mode of my 121GW.

Another thing happened today while testing for the first time. When I switched from left side off to V mode the meter did not turn on. I taped on the mode switch still in this mode and it turned on. So there must be another problem with my 121GW.

You can read my postings and realted answers if you want to get the complete story:
http://www.eevblog.com/forum/testgear/eevblog-121gw-discussion-thread/msg1446232/#msg1446232
http://www.eevblog.com/forum/testgear/eevblog-121gw-discussion-thread/msg1447697/#msg1447697
http://www.eevblog.com/forum/testgear/eevblog-121gw-discussion-thread/msg1447957/#msg1447957
http://www.eevblog.com/forum/testgear/eevblog-121gw-discussion-thread/msg1465469/#msg1465469
http://www.eevblog.com/forum/testgear/eevblog-121gw-discussion-thread/msg1469130/#msg1469130
http://www.eevblog.com/forum/testgear/eevblog-121gw-discussion-thread/msg1469890/#msg1469890
« Last Edit: April 08, 2018, 09:23:25 pm by Candid »
 

Offline Seppy

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Re: EEVblog 121GW Multimeter Issues
« Reply #180 on: April 09, 2018, 10:53:54 am »
I already posted in the discussion thread about a problem I have with Vac readings. Now I will switch to the correct place for this.

In 5Vac mode I get wrong readings.

Today I checked the ZERO OFFSET CALIBRATION and had to find out, that only in 5Vac range mode with shorted inputs I get a reading of 0,499xVac. With open input I get nearly the same value of about 0,5Vac.

In all other Vac (and Vdc) ranges I get 0,0xxV. So I tried to calibrate only the zero offset in Vac 5V range mode. During the count down it displays the 0,499xV and after the calibration I still have this offset with shorted inputs on the 5Vac range. At the end of the calibration countdown I see "OFF-E" for about half a second what is not mentioned in the manual.

I have two references from voltagestandard.com. The 121GW is spot on for all voltage measurements I can do (Vdc 0,350V up to 10.000V and Vac 5V).

So there must be something wrong with the 5Vac range mode of my 121GW.

Another thing happened today while testing for the first time. When I switched from left side off to V mode the meter did not turn on. I taped on the mode switch still in this mode and it turned on. So there must be another problem with my 121GW.

You can read my postings and realted answers if you want to get the complete story:
http://www.eevblog.com/forum/testgear/eevblog-121gw-discussion-thread/msg1446232/#msg1446232
http://www.eevblog.com/forum/testgear/eevblog-121gw-discussion-thread/msg1447697/#msg1447697
http://www.eevblog.com/forum/testgear/eevblog-121gw-discussion-thread/msg1447957/#msg1447957
http://www.eevblog.com/forum/testgear/eevblog-121gw-discussion-thread/msg1465469/#msg1465469
http://www.eevblog.com/forum/testgear/eevblog-121gw-discussion-thread/msg1469130/#msg1469130
http://www.eevblog.com/forum/testgear/eevblog-121gw-discussion-thread/msg1469890/#msg1469890

Thankyou for your message we are aware of your issue, the issue with the on-off is almost certainly due to the shim fix (this will be shipped to you at some point soon, it will resolve the issue if that is an issue). It does sound like your 5V AC range has an issue, there is a new firmware update coming out. It might improve the situation for you and if you did want to recalibrate it would be better to do it after the next update.
« Last Edit: April 09, 2018, 10:55:50 am by Seppy »
 

Offline Candid

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Re: EEVblog 121GW Multimeter Issues
« Reply #181 on: April 09, 2018, 03:47:06 pm »
Thank you for the response. I will try to calibrate with the next firmware update. I really wonder what the problem is. In all other ac/dc ranges the zero offset is ok so it hopefully is something that can be fixed with a firmware update.
 

Online Doctorandus_P

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Re: EEVblog 121GW Multimeter Issues
« Reply #182 on: April 15, 2018, 07:22:06 am »
Source code not available.
To me this was the biggest bug of them all and enough reason to not buy this meter.
I really would have liked to be able to add some customized measurements, without too much effort, but having to rewrite all firmware from scratch would cost me far too much time.

Maybe I'll revise my opinion when a "community" alternative version of the software for this meter becomes available.
 

Offline morrone

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Re: EEVblog 121GW Multimeter Issues
« Reply #183 on: April 26, 2018, 01:03:58 pm »
Bug in firmware 1.10:  If you try to start logging to the SD card while there is no SD card in the slot, the meter locks up.  Granted, user error, but it would be nice if the meter displayed an error rather than locking up.
 

Online EEVblog

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Re: EEVblog 121GW Multimeter Issues
« Reply #184 on: April 26, 2018, 04:17:24 pm »
Source code not available.
To me this was the biggest bug of them all and enough reason to not buy this meter.

Name another commercial meter on the market that has open source firmware?

Quote
Maybe I'll revise my opinion when a "community" alternative version of the software for this meter becomes available.

We encourage that.
 

Offline Candid

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Re: EEVblog 121GW Multimeter Issues
« Reply #185 on: April 28, 2018, 09:47:32 am »
I already posted in the discussion thread about a problem I have with Vac readings. Now I will switch to the correct place for this.

In 5Vac mode I get wrong readings.

Today I checked the ZERO OFFSET CALIBRATION and had to find out, that only in 5Vac range mode with shorted inputs I get a reading of 0,499xVac. With open input I get nearly the same value of about 0,5Vac.

In all other Vac (and Vdc) ranges I get 0,0xxV[...]

Thankyou for your message we are aware of your issue, the issue with the on-off is almost certainly due to the shim fix (this will be shipped to you at some point soon, it will resolve the issue if that is an issue). It does sound like your 5V AC range has an issue, there is a new firmware update coming out. It might improve the situation for you and if you did want to recalibrate it would be better to do it after the next update.
Ok the new firmware is out. I flashed v1.15 and tried again. But it is still the same. In 5Vac range I have an offset of about 0,5V (shorted or opened port is nearly the same). I tried to calibrate the zero offset for the 5Vac range but it did not help. So there must be a problem with the 5Vac range of my 121GW.

What can I do? The shim fix did not arrive up to now bot I don't think it will help with this.
 

Offline Iagash

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Re: EEVblog 121GW Multimeter Issues
« Reply #186 on: May 03, 2018, 06:17:59 am »
Firmware 1.15 has a regression vs. 1.10.

When connecting via bluetooth and disconnecting again by closing the app (or the bluetooth connection) no connection is possible until bluetooth is switched on and off on the meter.
 

Offline Seppy

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Re: EEVblog 121GW Multimeter Issues
« Reply #187 on: May 03, 2018, 11:13:30 am »
Firmware 1.15 has a regression vs. 1.10.

When connecting via bluetooth and disconnecting again by closing the app (or the bluetooth connection) no connection is possible until bluetooth is switched on and off on the meter.

That is unlikely as the Bluetooth is basically a UART-BLE bridge module and it hasn't been updated. It is more likely an update to windows or android that caused the issue, otherwise i'm not really sure how this could have happened.

One important thing to know is that if you simply minimize the app it is still using the bluetooth device until it is properly closed this means if you opened another instance it will not connect as the bluetooth device is already in use.
 

Online Scottjd

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Re: EEVblog 121GW Multimeter Issues
« Reply #188 on: May 03, 2018, 11:31:41 am »
Firmware 1.15 has a regression vs. 1.10.

When connecting via bluetooth and disconnecting again by closing the app (or the bluetooth connection) no connection is possible until bluetooth is switched on and off on the meter.

That is unlikely as the Bluetooth is basically a UART-BLE bridge module and it hasn't been updated. It is more likely an update to windows or android that caused the issue, otherwise i'm not really sure how this could have happened.

One important thing to know is that if you simply minimize the app it is still using the bluetooth device until it is properly closed this means if you opened another instance it will not connect as the bluetooth device is already in use.

Sounds  logical. As and admin do you have the power to modify the fist post in this thread?
I was thinking somehow of informing people when reporting issues to include as much details as posable. As with most trouble shooting issues or working on replicating the same issue the more details the better.
Like the OS or remote device being used to connect to the meter via Bluetooth. What app was used, and what version of the app used? And so on?
It’s usualy a time saver and others besides admins and EEVBlog employees can try to replicate the same issue and help confirm if it’s an issue that affects all or just one persons systems from an bad registered driver or older app version.
Just a thought?
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Offline Iagash

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Re: EEVblog 121GW Multimeter Issues
« Reply #189 on: May 03, 2018, 08:12:10 pm »
Firmware 1.15 has a regression vs. 1.10.

When connecting via bluetooth and disconnecting again by closing the app (or the bluetooth connection) no connection is possible until bluetooth is switched on and off on the meter.

That is unlikely as the Bluetooth is basically a UART-BLE bridge module and it hasn't been updated. It is more likely an update to windows or android that caused the issue, otherwise i'm not really sure how this could have happened.

I did some more tests and I guess it's the decreased data rate, that seems to cause a longer time to be able to reconnect. It just needs a lot longer until a reconnect is possible. I guess the BLE module resets the connection, when some buffer overflows when it couldn't send the data for some time making a new connection possible.
 

Offline Candid

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Re: EEVblog 121GW Multimeter Issues
« Reply #190 on: May 06, 2018, 09:26:11 am »
Didn't I already read about this? I am not sure so I post it here in the issues thread.

When I turn off the beeper and afterwards go to diode test I get a nonstop beep with firmware 1.15.

PS: On 19th april I got a message telling me that the repair parts for the 121GW have been sent to me. They still not arrived ;-(
 

Offline Seppy

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Re: EEVblog 121GW Multimeter Issues
« Reply #191 on: May 07, 2018, 11:19:39 am »
Didn't I already read about this? I am not sure so I post it here in the issues thread.

When I turn off the beeper and afterwards go to diode test I get a nonstop beep with firmware 1.15.

PS: On 19th april I got a message telling me that the repair parts for the 121GW have been sent to me. They still not arrived ;-(

That is another strange issue your meter has, do you have steps to reproduce? I've tried a few things and couldn't get it to hold on beep.
 

Offline knapik

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Re: EEVblog 121GW Multimeter Issues
« Reply #192 on: May 07, 2018, 11:30:10 am »
I believe that I used to have the same issue, and it was due to the wobbly knob not making correct contact with the pads.
 

Offline Candid

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Re: EEVblog 121GW Multimeter Issues
« Reply #193 on: May 07, 2018, 05:15:23 pm »
Ok so I will go on waiting for the replacement parts and hopefully they will solve bot problems I have. I think I can remember that I already read about someone having this issue too here but could not find the post.
 

Offline Seppy

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Re: EEVblog 121GW Multimeter Issues
« Reply #194 on: May 16, 2018, 05:40:25 pm »
@ Candid

Did you receive your shims and whatnot, any update with the issue you were having?
 

Offline Candid

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Re: EEVblog 121GW Multimeter Issues
« Reply #195 on: May 16, 2018, 11:23:18 pm »
@ Candid

Did you receive your shims and whatnot, any update with the issue you were having?
No, I did not receive anything up to now. And no update to the issue except that it is getting worser. Very often from off to any position the meter stays off or resets/starts from time to time and still having the +0,5V with shorted leads on ac 5V-range.

I got the mail about the delivery on 19th May but without any tracking Url. Maybe you can track something but not me:
Your order is on its way!

We are pleased to confirm that your order has now been shipped.

    Our Reference: 11633

    Your Reference:

    Carrier: Plain Labels
    (Australia Post for within Australia)

    Carrier's Reference:

    Tracking Url:
 

Offline Candid

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Re: EEVblog 121GW Multimeter Issues
« Reply #196 on: May 17, 2018, 09:24:03 pm »
Today I got the switch and shim and installed them. So now the known issue seemes to be fixed.

But the fault concerning my 0,5Vac offset with shorted input in the 5Vac range still exists. So there must be something else with my meter.
I have firmware 1.15 installed and I just tried ZERO offset calibration of the 5Vac mode and it is still at about 0,5Vac with shorted input. When I open the input it is slightly higher (about 0,499xV against 0,515xV). The other Vac ranges are ok this only applies to the 5Vac range.
« Last Edit: May 17, 2018, 09:40:40 pm by Candid »
 

Online Scottjd

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Re: EEVblog 121GW Multimeter Issues
« Reply #197 on: May 19, 2018, 08:30:46 pm »
Has anyone reported or noticed when you zero out the meter on voltage or resistance (I think all settings) and use the auto hold at the same time, the auto hold results ignore the zero out value when it displays the auto hold results.

Then if you turn off the Auto hold the relative triangle symbol is still displayed on the meter, but it’s not the truly zeroed out value being displayed. It’s the normal value ignoring the relative value it should be doing math with like you didn’t zero it at all. But the triangle is still displayed on the LCD. So I pushed the relative button again, instead of the triangle turning off it blinks on and off real fast and sets a new zero value.

Or, once you get the Auto hold reading without the relative value calculated into the Auto hold reading displayed, then turn off the relative set value by pressing the button again the triangle on the LCD does turn off and the Auto Hold is still displayed on the LCD. But it’s not doing any auto holding despite the LCD showing Auto hold being displayed, the meter will display the live readings with no holding at all or beep indicating it’s captured a hold.

Seems these two functions just don’t know how to work together or play nice with each other.

The other thing I noticed with Auto hold is it seems to have difficulties capturing changes in values when the meter is set in a manual range instead of auto ranging. I set the meter to a manual range, and probe the DUT like voltage from my power supply or voltage reference so I know it’s a steady contact source. No beep, not auto hold after maybe 5 to 8 seconds. So I remove the probes and try again, sometimes it will work the second time, sometimes it won’t. Then I try again if it doesn’t work and eventually it will beep and display the hold value captured. This issue seems intermittent. I tried it also changing the voltage when it didn’t work and still had the same intermittent issue, and I’m not talking about small changes in the value. I tested this with 2.5VDC differences or 5VDC differences in the voltage.

And then also Auto hold might capture a value and beep, but if you don’t immediately remove the probe from the point being measured really fast it will display a lower value as you disconnect the probes from the source.
Example, let’s say I’m measuring a 5V source. When it does a hold and then beeps, if I hesitate and wait a second before I remove the probe it will change from 5V to a lower value like 3.856V as I remove one of the probes. So I have to take a reading again and wait for the beep, and remove the probe from the points I’m messing really fast for it to keep and hold the 5V measurement on the display. The voltage source doesn’t change and stays powered on the whole time.

And it doesn’t detect small changes like mV or uV changes even when it’s set to the highest resolution using auto range or selecting a manual range. I think it’s looking for pre-set amount of change in the value it’s measuring before it will display a new hold value. I’m not sure how much difference it needs to see before it captures and display the new hold value? I think it’s between 35mV and 40mV?
I found myself reversing the probes between each reading before taking probing the next reading. This way I forced it to the negative value before taking the next reading so it would capture even the smallest change in the next reading in case the next reading didn’t have a big enough change in value that would result in dillaying the same reading as before. No new beep if the value change isn’t big enough, or you start to think it’s just not working on the next reading you take.

And I know this is common with some meter, so maybe I shouldn’t mention this next one. But like some other cheap meters the reading are more accurate if you don’t use auto hold compared to the auto hold results. This might be from the meter displaying the results to fast before the measument settles all the way or not taking a few samples before display the hold number?

As I type this I’m starting to realize the auto hold might be the main issue from the fist thing I wrote about using auto hold with a zero set relative value first. I think Auto hold needs a little code tuning in the firmware.

Latest firmware 1.15, just recveied it today.
Scott
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