EEVblog 121GW Multimeter Issues

[JS]

About leaking batteries, just replace them every a year or two, that's all it takes, even ig they are not fully depleated, and use them till they die in the mouse, tv remote or torch.

That's not all it takes, unfortunately. I've had batteries well under a year old that weren't depleted pop on me. I think they aren't building them as heat resistant as they used to. I have become pathological about checking on my alkalines now because they seem to pop on me all the times these days and they never used to do that.

I don't know if you canmake a claim, they aren't supposed to leak so easily, after expiration day or really abused. Alkalines can take a fair share of abuse, not as sensitive as lipo where a short will most likely make them explode, or being too empty, or too full, or too warm, or too cold, or you get my point...

You should swap brands or something, I don't see blown batteries that often, a calculator I got from a friend, parched a few traces in the keyboard and got away with it and, a tv remote or two, where the things last for ever, and some really old stuff forgotten with the batteries on. I don't use cheap batteries either, I mostly gpt them from a friend's music shop who buys mostly for personal use, replace or fit in products, so I get them for cheap or free, but still you won't loose your salary over different brands.

JS

[darik]

About leaking batteries, just replace them every a year or two, that's all it takes, even ig they are not fully depleated, and use them till they die in the mouse, tv remote or torch.

That's not all it takes, unfortunately. I've had batteries well under a year old that weren't depleted pop on me. I think they aren't building them as heat resistant as they used to. I have become pathological about checking on my alkalines now because they seem to pop on me all the times these days and they never used to do that.

I don't know if you canmake a claim, they aren't supposed to leak so easily, after expiration day or really abused. Alkalines can take a fair share of abuse, not as sensitive as lipo where a short will most likely make them explode, or being too empty, or too full, or too warm, or too cold, or you get my point...

You should swap brands or something, I don't see blown batteries that often, a calculator I got from a friend, parched a few traces in the keyboard and got away with it and, a tv remote or two, where the things last for ever, and some really old stuff forgotten with the batteries on. I don't use cheap batteries either, I mostly gpt them from a friend's music shop who buys mostly for personal use, replace or fit in products, so I get them for cheap or free, but still you won't loose your salary over different brands.

JS

You think I haven't tried different brands? I've tried everything. It just doesn't matter unless I'm checking once a month or more a popped AAA or AA always sneaks up on me. AAAs are the worst. I recently had two Energizer AAA go in a laser pointer that were only 6 months old and they were still reading 1.2V and working fine. My understanding is there's a sealed plastic membrane of some kind inside them that pops. And it seems like that membrane is more delicate than it used to be. I wish I knew what causes it, but it's not age or being deep discharged.

Up until 2010 or so this NEVER happened to me with alkalines, now it happens all the time. Something has changed.

[JS]

About leaking batteries, just replace them every a year or two, that's all it takes, even ig they are not fully depleated, and use them till they die in the mouse, tv remote or torch.

That's not all it takes, unfortunately. I've had batteries well under a year old that weren't depleted pop on me. I think they aren't building them as heat resistant as they used to. I have become pathological about checking on my alkalines now because they seem to pop on me all the times these days and they never used to do that.

I don't know if you canmake a claim, they aren't supposed to leak so easily, after expiration day or really abused. Alkalines can take a fair share of abuse, not as sensitive as lipo where a short will most likely make them explode, or being too empty, or too full, or too warm, or too cold, or you get my point...

You should swap brands or something, I don't see blown batteries that often, a calculator I got from a friend, parched a few traces in the keyboard and got away with it and, a tv remote or two, where the things last for ever, and some really old stuff forgotten with the batteries on. I don't use cheap batteries either, I mostly gpt them from a friend's music shop who buys mostly for personal use, replace or fit in products, so I get them for cheap or free, but still you won't loose your salary over different brands.

JS

You think I haven't tried different brands? I've tried everything. It just doesn't matter unless I'm checking once a month or more a popped AAA or AA always sneaks up on me. AAAs are the worst. I recently had two Energizer AAA go in a laser pointer that were only 6 months old and they were still reading 1.2V and working fine. My understanding is there's a sealed plastic membrane of some kind inside them that pops. And it seems like that membrane is more delicate than it used to be. I wish I knew what causes it, but it's not age or being deep discharged.

Up until 2010 or so this NEVER happened to me with alkalines, now it happens all the time. Something has changed.

Have you contacted energizer?  Use them all the time, one of the few brands I use, and never seen one leaking, what enviroment do you usually have? Where I live 40°C is not unussual, humidity well over 90% most nights.

JS

[gdewitte]

The fine print on most of the packages for alkaline batteries requires that you contact the manufacturer, that you are responsible for shipping any damaged items back to them for replacement, and the replacement will be an "equivalent" device. I've had some "new" AA alkalines leak when they were in one of those handy battery storage carriers (e.g., Powerpax Storacell).

[IanB]

I wish I knew what causes it, but it's not age or being deep discharged.

Up until 2010 or so this NEVER happened to me with alkalines, now it happens all the time. Something has changed.

I think what has changed is "High Power" or "Super Extra Power" or "Ultra Performance".

The marketing people have been pushing for more buzzwords on the packaging. To increase the performance of the batteries the chemical formulation has been made more and more active. This means the chemicals inside the battery can react and produce hydrogen even when the battery is not being used. The hydrogen increases the pressure inside the cell until it is too much, when the gas pressure breaks the seal and pushes the electrolyte out of the casing.

The best solution is to avoid all the expensive, high performance brands and buy the cheap dollar store brands instead. The cheaper cells use the older, less active formulations and don't have the same leaking tendency.

I have been buying Sunbeam branded batteries for a while at 4/1$ and I haven't seen one leak yet.

[darik]

Have you contacted energizer?  Use them all the time, one of the few brands I use, and never seen one leaking, what enviroment do you usually have? Where I live 40°C is not unussual, humidity well over 90% most nights.

My apartment only has windows in the west and the evening sun can really cook the place. I'm pretty sure at least once it was caused by the thing sitting in a spot where a sunbeam was on it for a while. But I think batteries should be able to survive sitting in direct sunlight.

I think what has changed is "High Power" or "Super Extra Power" or "Ultra Performance".
...
The best solution is to avoid all the expensive, high performance brands and buy the cheap dollar store brands instead. The cheaper cells use the older, less active formulations and don't have the same leaking tendency.

That's a very good theory. I tried buying premium batteries and that sure didn't work. I never once had an alkaline leak on me until well after 2000. I'd be happy to go back to an old design.


Looks like that's what I'll be doing in my 121GW. It would be nice to know officially if lithiums are a bad choice and to see that added to the manual.

[JS]

Looks like the ultra performance batteries didn't reach our sudamerican market, one nice thing of living that far south...

JS

[EEVblog]

Looks like that's what I'll be doing in my 121GW. It would be nice to know officially if lithiums are a bad choice and to see that added to the manual.

Confirmed. Fresh Lithium cells produce an overvoltage on the reference on both diode and ohms ranges. Don't use fresh Lithiums and these ranges.
The manual will be updated, and a possible future fix allowing this investigated.

[tomp]

Possible an issue with the range switch:
 - disconnect any leads
 - turn beep off in setup
 - rotate range switch to resistance/continuity/...
 - press "Mode" and switch it to continuity (the meter remembers the mode)
 - rotate the range switch to "mVA/VA" while applying a small pressure to it (when you are very careful and do not apply any pressure, it does not do that)
 - the meter will beep during the switching
 - you can even find a position of the range switch where the meter reads 0 ohms and beeps continuously
My meter is a Kickstarter one - Johnny B. Goode, delivered by Welectron.
Video showing the problem:

[Scottjd]

Possible an issue with the range switch:
 - disconnect any leads
 - turn beep off in setup
 - rotate range switch to resistance/continuity/...
 - press "Mode" and switch it to continuity (the meter remembers the mode)
 - rotate the range switch to "mVA/VA" while applying a small pressure to it (when you are very careful and do not apply any pressure, it does not do that)
 - the meter will beep during the switching
 - you can even find a position of the range switch where the meter reads 0 ohms and beeps continuously
My meter is a Kickstarter one - Johnny B. Goode, delivered by Welectron.
Video showing the problem:

I think this is because of the jack detection for current ranges and because you have it in continuity mode. I think pressing down is spreading the switch wipers giveing the meter less time to recognize the mode change as the wipers are spread out more between the traces on the PCB.
It’s still beeping even with beep off because the current jack detection and continuity will still beep with beep off in the settings.
I may be wrong, but I think this is just giving the meter a few less milliseconds to figure out the mode changed by spreading the wipers from the pressure.
It’s only an issue if both modes make contact at the same time. But it can also be argued this is only an issue if you have current applied to the meter and you really should not be changing modes with an active DUT powered up and plugged into the meter.

[tomp]

I think this is because of the jack detection for current ranges and because you have it in continuity mode.

It is probably not the jack detection thing. It seems that there is a position of the range switch between "ohm" and "mVA/VA", where the meter is still switched do "ohm", however it reads short. In principle, I do not mind that, other meters do similar things, however the 121GW switch does not have the best indent, it is very easy to accidentally leave it in an intermediate position. However, the fact that the meter beeps when switching ranges even when it should not is quite annoying. Even if I do not apply any pressure on the switch and I try to switch as fast as possible, it beeps in 10 % of cases.

[Digital Corpus]

That'd be consistent with minor tolerances of the trances for the switch and being between modes. The added pressure flattened the contact wider with a slightly larger than normal contact area causing it to just barely switch part of one position and the next at the same time. Could also be a result of solder mask tolerances. This could literally be an edge case.

[ButterToast1134]

Is anyone having bluetooth connectivity problems?

My meter does not want to connect to through bluetooth.
My buddy's meter he can connect to it using his Android and I can connect to his using my Iphone.
My meter however will not show up on either phone.
When holding the bluetooth button it says its active but can't see it with any phone or devices.
Any one have any suggestions?

Oh if it matters my SN is EEVBLog 001563

Thanks

I said my a lot.

MINE! MINE! MINE!

[IanB]

My meter connects fine to my Apple devices. However, I had lots of trouble with Windows 10. It connected one day and not the next. I had to reboot to fix it.

What firmware do you have on the meter? You might wish to update to the latest v1.26 if you have not done so already.

Also, make sure you are using the right app. There is an obsolete app floating around somewhere that is no good. You need to make sure you get Dave's current 121GW app.

[JS]

First activate bluetooth on the phone, close everithing, activate bluetooth on the meter, once activated open the app, if it doesnt show press refresh. I uave build 9 on android and works fine.

JS

[ButterToast1134]

Well as I said my buddys 121GW will connect to my phone.

My meter does not show up on his phone or my phone.

His meter connects flawlessly.

I have build 1.7 App even though his connects to mine.
Just did a firmware update today so I am running the 1.26 on the meter still doesnt work.

This leads me to believe there is a problem with the bluetooth module on the meter.

No devices can see it.

[JS]

Bummer!

  I've heard of some BT modules without the proper FW, there are no terminals installed in the BT module but I believe there are pads to connect there. If that's the case you could probably take the dumps from the thing in your friends and take it to yours, I haven't seen those online, I've seen them from the STM firmware. If you do you could send them to Thomas, who's getting a lot of info for reverse engineering the meter, he has a lot of info in it.

https://github.com/tpwrules

  Of course you could talk to Dave and hear what he has to say, but he will most likely encourage you to "take it apart!!" and try to fix it yourself if you believe you can. I don't think there's a warranty void if removed sticker, it might have one if not removed!

JS

[IanB]

This leads me to believe there is a problem with the bluetooth module on the meter.

No devices can see it.

You probably need to contact Dave for a replacement meter, unfortunately. They probably would like you to send the meter back to them so they can investigate what is wrong.

[chronos42]

First activate bluetooth on the phone, close everithing, activate bluetooth on the meter, once activated open the app, if it doesnt show press refresh. I uave build 9 on android and works fine.

JS

That does not work for me. When I first tried the bluetooth function that drove me nuts.
The App seems to have a problem either with my Nokia 8 or Android 8.1.

What I did:
Activate bluetooth at the phone and let it seach for a new device.
Activate bluetooth at the 121GW, the meter is detected by the phone and will connected to the meter.
Until this point everything is ok, the phone is connected to the meter.

Start the Android app and nothing happens...mostly only an empty screen, that`s all, the app does not see the meter. Sometimes it worked for some reason, mostly it does not.
 
I found this solution:
Connect the meter to the phone as described.
Open the app.
In case that nothing happens: Switch off the bluetooth function at the meter and switch it on again immediately.
Than the app shows the meter ID.
Confirm the meter ID and the app connects and works without any problem from now on.

[chronos42]

Hi,
I noticed that the meter is locked in a auto-ranging loop in the DC+AC mode in some conditions (Ver. 1.26).

For example: Genrate this signal with a function generator:
6.4Vss, sinus, 800Hz together with a DC offset of +6.6V.

I've seen this very same auto-ranging loop in AC+DC simply measuring the mains 50 Hz, 230 V.

Regards.

I've seen it too, unable to repeat as I turned off and on again and was good.

JS

It is easy to repeat:
Set the meter to AC and connect it to the 230V mains.
Then change from AC to DC+AC and the auto-ranging loop occures.

This should be fixed in the next firmware.

[JS]

It happend to me in a very differemt situation, measuring a DC IIRC, the meter was already set to AC+DC, I switched it on and connected the source. But as I said, I couldn't repeat it.

JS

[JS]

Maybe your meter got in sync with your phone, and being already linked is bringing problems for you. You could try connect them both via th bluetooth menu in the phone and then making it forget the connection.

JS

[Dr. Frank]

I have now replaced D7, D8 by two BF256B, n-JFETs. They show leakage currents of the Gate vs. Drain/Source reversed diode of < 20pA @ up to 20V, and as expected no zener effect, as they are specified up to 30V D-G and S-G voltage. The B-E diode of a BC547 transistor also had very low leakage in the pA range, but started to zener at about 6..7V, as expected.
 



The assembly was a bit tricky, because there is only 5mm clearance above the PCB, and I had to bend flat the metal shield of the battery case a bit.

After assembling these FETs, I observed big deviations in the 50M and 5M Ohm ranges, so I cleaned this area on the PCB, around the U9 multiplexer.

After drying, the Ohm ranges were again spot on.
Additionally, I observed that concerning the leakage effect in the 50 mV dc range of about 170pA:
https://www.eevblog.com/forum/testgear/eevblog-121gw-discussion-thread/msg1728887/#msg1728887

the 50mV range now shows a few µV only, when left open, so leakage should be <1pA.

Therefore I assume, that I also removed the leakage path on pin 14 of U9.

Frank

[chronos42]

Hi Frank,

the maximum forward gate current of the the BF256 is 10mA. So I assume this is not joeqsmith compatible...

BTW: A MMBF5457 would better fit mechanically.

[CDaniel]

A "normal" test for average user should be at least mains voltage in resistance mode ... then is a fix .