EEVblog 121GW Multimeter Issues

[crispus]

I'd also be happy to settle for an affordable PCB replacement, if that would be an option. Anything really since now I've just got a very expensive paper weight.

I would be interested in this option too since my most expensive multimeter is useless. I asked about this option in this thread couple months ago but no response so far...

Is there a board replacement available? That would give me peace of mind...

[jancumps]

I've tried to make a bit more targeted photos of my meter (SN 180701835 that is behaving well).

I can see some damage on that PTC and the shrink around it.

(the DMM case side is not damaged. What looks like damage is shadow of the component)

[J-R]

I've tried to make a bit more targeted photos of my meter (SN 180701835 that is behaving well).

I can see some damage on that PTC and the shrink around it.

(the DMM case side is not damaged. What looks like damage is shadow of the component)

Not sure if you're asking for info or just pointing this out, but of course future readers should push the metal shield tight against the side of the bottom case before re-assembly to avoid damaging the PTC.

[EEVblog]

FYI, I have asked KaneTest for comment.

[EEVblog]

FYI, I have asked KaneTest for comment.

They have come back and said they can't see how it could have survived the factory calibrator HV test if it was a manufacturing error. But they have agreed to replace it. So email me your courier details.

[jancumps]

I've tried to make a bit more targeted photos of my meter (SN 180701835 that is behaving well).

I can see some damage on that PTC and the shrink around it.

(the DMM case side is not damaged. What looks like damage is shadow of the component)

Not sure if you're asking for info or just pointing this out, but of course future readers should push the metal shield tight against the side of the bottom case before re-assembly to avoid damaging the PTC.

I wasn't asking. Just showing how the PTC area and shield looks like in my meter. It may help in the analysis.

[Archon]

Hi, new user here. Is this the right place to ask if the above issue was related to manufacturing during the kickstarter? Did it result in a fix of some sort? If I were to order a 121GW right now, can I have confidence it won't have such an issue?

[HKJ]

Hi, new user here. Is this the right place to ask if the above issue was related to manufacturing during the kickstarter? Did it result in a fix of some sort? If I were to order a 121GW right now, can I have confidence it won't have such an issue?

As far as I know the only real issue was with the rotary switch and it was fixed in a couple of months.
Over time there have been some software issues, but nothing you could not get around by using manual range and because the 121GW allows software updates it has been possible to fix these issues on all meters sold.

Note: I do not rate the 121GW as the best DMM ever, but it is a very good meter and like any meter it is not perfect. I do have about all high end meters on the market and I would not rate any of them a clear winner.

[EEVblog]

Hi, new user here. Is this the right place to ask if the above issue was related to manufacturing during the kickstarter? Did it result in a fix of some sort? If I were to order a 121GW right now, can I have confidence it won't have such an issue?

The PCB shim issues was limited to the first few thousands PCB's. That included all the Kickstarter units and a bunch of the first normal production units. All future PCB's have been the correct thickness and the issue was resolved. All units bought today do not have this issue, no one has old stock.

[nuclearcat]

Hi, new user here. Is this the right place to ask if the above issue was related to manufacturing during the kickstarter? Did it result in a fix of some sort? If I were to order a 121GW right now, can I have confidence it won't have such an issue?

The PCB shim issues was limited to the first few thousands PCB's. That included all the Kickstarter units and a bunch of the first normal production units. All future PCB's have been the correct thickness and the issue was resolved. All units bought today do not have this issue, no one has old stock.

Sorry to ask here, but where to get this shim? I am one of "early kickstarter users", used multimeter very rarely, and i started to get contact issues (i have to press on knob to make multimeter on after changing mode).
Maybe there is some drawings and anything i can do DIY?

[BrianG61UK]

Using  low-Z the voltage disappeared.  I read up on ghost voltage.  Yep, that was what I saw.
Thanks for your assistance.

Surely that means your ground is a high impedance, which means it's not ground at all and could be dangerous if you use it to ground something that needs a ground for safety reasons.

It could be induced voltage from a parallel running cable, however I'd recommend it's investigated by a qualified electrician using an installation tester.

I was forgetting that the 121GW in Low-Z mode is brain dead and shows zero even when there is a low voltage present.

[ShortCircuit]

I just checked my meter and mine too has the plastic insulator deformed by squishing the PTC, not enough to do damage though. Looks like the metal shield with insulator wasn't glued to the side of the case, which would've prevented this. I took the liberty of applying a piece of inflammable PSA tape to secure it to the case and prevent subsequent smoke egress and grief.

[oliv3r]

Hi everyone.
It seems my 121GW just broke, and I have no idea how or why :S
...

Hey @vyruz I'm sad to see your broken DMM I recall you got a replacement however, yeah? Do you still have the broken one? Would you want to offer it for science? Some of us are curious to get hi-res pictures/scans of the PCB; which would require removing all components first of course. Only a ruined DMM should be used for that of course

[ShortCircuit]

Did anyone else notice that turning the bluetooth on causes the meter to cool by more than half a degree C and turning it back off causes it to heat back up to previous half a degree higher temperature?

[bicycleguy]

@ShortCircuit
Good find!  and I thought I was picky.  Mine is almost exactly 1 degree F 

[Kleinstein]

The meter should not cool down form turning on blue-tooth. If at all the temperature reading may change, by some interference.
The temperature reading is likely not that accurate anyway, so I would not worry much about this part. The question is if it effects other measurements too ?

[Kean]

Did anyone else notice that turning the bluetooth on causes the meter to cool by more than half a degree C and turning it back off causes it to heat back up to previous half a degree higher temperature?

I can confirm this happens on my 121GW.  Drops about 0.6C within a few seconds when BT is turned on, and rises again very quickly after it is turned off.
The thermistor NTC1 which I presume is used for temperature sensing is at top right of the PCB (looking from the back) and BT module at top left.
I hooked up some fine wires so I could monitor B+, VDD (3.6V), and VDD_P (3.3V) with the case closed.  The thermistor is part of a voltage divider on VDD.
VDD and VDD_P do not really change when BT is enabled, but I do see a small drop on B+ due to the extra load.
VREF+ on the STM32 connects to VDDA which connects to VDD_P.  No idea... maybe a firmware issue with code trying to correct for something no longer relevant?

[Kean]

The temperature reading is likely not that accurate anyway, so I would not worry much about this part. The question is if it effects other measurements too ?

It is used for CJC with the thermocouple, so thermocouple readings also drop by the same amount.
Weird that they put the thermistor so far away from the input jacks when it is used for CJC.

[CompNut]

I just received my meter today from Amazon.  The app connects to the meter but does not display anything.  I tried the Meteor app and that works.  I am using an LG V60 with Android 10.

[vulpes]

Is this meter worth getting now? Have the firmware issues been fixed after some years in production?
I'm torn between this and Brymen 869, but I'd appreciate a smaller size and Bluetooth on GW121.

Thanks!

[BILLPOD]

Posted by: vulpes
« on: Yesterday at 08:31:30 am »

    Insert Quote


Is this meter worth getting now? Have the firmware issues been fixed after some years in production?
I'm torn between this and Brymen 869, but I'd appreciate a smaller size and Bluetooth on GW121.

Good Morning Vulpes,   I got my GW121 about a year ago and mine works beautifully.  No issues whatsoever.  It has become one of my favorites.   

_

[vulpes]

Thanks for the response. Is the continuity mode fast now, since I will be using it a lot? And when it comes to the readings speed, are you satisfied with it? Sluggishness of the meter seems like the most commonly mentioned issue of the GW121.

[BILLPOD]

Good Morning Vulpes,  The 121 is as fast as any of my meters,
which include Flukes and Brymens.   What I love is the ability to use  the continuity feature in what I call 'reverse mode', where you can set it to beep on broken continuity,....great for checking
the integrity of wires and cables.   

[J-R]

Continuity speed was never an issue with the 121GW as far as I'm aware, but the resistance autorange speed is on the slow side.  That has not changed.

In general it's a slow DMM, although it depends slightly on what you're doing with it.  Probably slowest DMM I've ever seen personally is the Keysight U1461A when set to autoV with DC+AC on the secondary display.  Can be many seconds for it to come to its senses.  Basically it has to decide AC or DC and the range for the primary, then calculate the secondary display.  In other configurations is plenty fast.

So consider your use case.

Nothing compares to a fast bench DMM with a VFD display.  I had previously suggested the Fluke 8840A/8842A with Slow/Medium/Fast modes.  In medium/fast it's about as instant as you can get.  Resistance from full scale to zero is maybe 1/4 second.

[jeraymond]

Hello — I'm seeing a problem where the 121gw shows incorrect frequency period. From my waveform generator I feed in a 0-5 V square wave at 1 kHz with a 50% duty cycle. The meter correctly shows a 1.0000 kHz for frequency, but a period of half the expected value at 0.4999 ms. Oddly adjusting the duty cycle changes the period measurement as well. With a 70% duty cycle at 1 kHz the period now reads 0.6999 ms. It seems to be missing the later half of the waveform in the period measurement.

Anyone else see this problem? I'm running the latest 2.05 firmware.