EEVblog 121GW Multimeter Issues

[BillB]

1) Purchased. 
2) Plugged in leads that came with the meter. 

Just for the record, were the leads you received made by Brymen or UEI ?.

At different times I believe both brands have been supplied with the 121GW and I'm pretty sure the UEI leads have a really long strain relief on the banana plug end. I received the Brymen leads with the BM-235 and have found them rather a tight fit in some other meters such as the Flukes.

I don't recall and I don't have the unit in front of me right now, but I'll check them tonight.  The plug end banana lanterns did not seem to be a problem, they fit in the jacks relatively easily, and fit into other equipment without a problem.  The lanterns on the pointy probe end are a different story; at ~4.69mm they are very tight.  If anything I would be leery of shoving them into these shrouded-type jacks.

[Muttley Snickers]

Sorry, I overlooked your previous post where you mentioned the lanterns for the tips. If the leads you received came with the screw on lanterns then they are most likely the Brymen leads as the UEI leads were not supplied with them. More information on both lead sets can be found on the page linked below.

https://www.eevblog.com/forum/testgear/eevblog-121gw-discussion-thread/1030/

[joeqsmith]

Dave,

I'm not sure if this is an issue or not, so feel free to erase it. 

Way back when you sent me the prototype meter, it included some really old firmware and you supplied me with what documents you had at the time.   At that time the alignment procedure was not included in the user's manual.   When I attempted to upgrade the firmware on this meter, the calibration was no longer valid.   I think this was something you had posted about or covered in Amp hour.   I made some transfer standards using my bench meter and realigned it.   I took some notes about what I had done and called it good enough.   

There is a member attempting to realign their meter and they ran into a problem.
https://www.eevblog.com/forum/testgear/hear-kitty-kitty-kitty-nope-not-that-kind-of-cat/msg2790680/#msg2790680

Looking at the various manuals that were made available that include the alignment procedure, it appears that they changed it.  I suspect based on what this person has found and having gone through it myself,  this is the reason the meter is no longer able to read down into the 100pF ish values. 

[EEVblog]

Dave,
I'm not sure if this is an issue or not, so feel free to erase it. 
Way back when you sent me the prototype meter, it included some really old firmware and you supplied me with what documents you had at the time.   At that time the alignment procedure was not included in the user's manual.   When I attempted to upgrade the firmware on this meter, the calibration was no longer valid.   I think this was something you had posted about or covered in Amp hour.   I made some transfer standards using my bench meter and realigned it.   I took some notes about what I had done and called it good enough.   

Anything related to the prototype meter I sent you should have no relevance to any production meter, this is why I specifically told you at the time not to test it or review it, it was just for shit'n'giggles to watch the magic smoke escape.

There is a member attempting to realign their meter and they ran into a problem.
https://www.eevblog.com/forum/testgear/hear-kitty-kitty-kitty-nope-not-that-kind-of-cat/msg2790680/#msg2790680
Looking at the various manuals that were made available that include the alignment procedure, it appears that they changed it.  I suspect based on what this person has found and having gone through it myself,  this is the reason the meter is no longer able to read down into the 100pF ish values.

I don't recall changes to the calibration procedure.

[joeqsmith]

Dave,
I'm not sure if this is an issue or not, so feel free to erase it. 
Way back when you sent me the prototype meter, it included some really old firmware and you supplied me with what documents you had at the time.   At that time the alignment procedure was not included in the user's manual.   When I attempted to upgrade the firmware on this meter, the calibration was no longer valid.   I think this was something you had posted about or covered in Amp hour.   I made some transfer standards using my bench meter and realigned it.   I took some notes about what I had done and called it good enough.   

Anything related to the prototype meter I sent you should have no relevance to any production meter, this is why I specifically told you at the time not to test it or review it, it was just for shit'n'giggles to watch the magic smoke escape.

There is a member attempting to realign their meter and they ran into a problem.
https://www.eevblog.com/forum/testgear/hear-kitty-kitty-kitty-nope-not-that-kind-of-cat/msg2790680/#msg2790680
Looking at the various manuals that were made available that include the alignment procedure, it appears that they changed it.  I suspect based on what this person has found and having gone through it myself,  this is the reason the meter is no longer able to read down into the 100pF ish values.

I don't recall changes to the calibration procedure.

Comparing the prototype with the old production meters, there doesn't appear to be any changes that would have effected the alignment procedure but I can certainly understand being concerned about releasing this information into the public domain.   From our original conversation when you supplied these documents, I will not make them available. 

I may align one of the old production meters using the original procedure to see if I can improve the lower readings.   At least it would be a data point for you if you do decide to look into it.   

[joeqsmith]

Using the original alignment procedure supplied with the prototype does indeed improve the the older production meter's lower end.   I'll add a demo of it in the next segment comparing it with the factory cal.    I will not disclose anything beyond what's been mentioned here.   

I'm not seeing a downside beyond the added time required to perform the additional steps.

[EEVblog]

UPDATE:
The issue with the cracked input jacks is as several suspected, a molding issue.

input jacks which were injected from the uncompletely-cleared mould probably resulting in for ABS mixed with any foreign materials so the injected jacks could be more easily broken.

Units potentially affected are with serial numbers S/N 18087001 to 181008000
The sockets for these were manually inspected for this issue but it seems that some slipped passed the inspection and have resulted in cracking.

They also mention the Brymen leads are not ideal:

2. Our input jacks were designed to be ideally matched with our test lead probe with 4.2 - 4.3 phi.  However, Brymen's probe has 4.5 - 5.0 phi, which can give more mechanical stresses to our input jacks.

"Phi" means diameter of the banana plug.
I'm not sure about their measurements because I measured the Brymen at 4.3mm or a smidge over. The UEi ones are spot on 4mm and not the lantern type ones the Brymen use.
They aren't saying don't use the Brymen leads, just that could be a contributing factor in this case. Welectron have been supplying Brymen leads.
My new stock of meters will all come with UEi leads.

They will be sending me a bunch of replacement jacks so I can send to people who want that option.
If you have been affected by this and prefer to replace it yourself, please email me your address so I can send you one. Use the email Title "121GW Connector"
Alternatively you send your meter back to UEi at this address. I'm not sure if they will rework or replace the meter or board.

Attn: (Mr.) Heegoo Kang
Tel: 82-32-837-5777
309, A-dong, Smart Valley,
Songdomirae-ro 30, Yeonsu-gu, Incheon,
21990, Korea

[EEVblog]

FYI, UEi vs Brymen plug

[BillB]

Thanks for the quick update Dave.  I'll be sending an email to get a replacement jack assembly from you as I'm pretty sure that my SN is within the affected range, though it's a shame that you've got to go through this. 

I think the response from UEi is a tad bit of a cop-out, and that any jack on a higher-end meter should be designed to handle the common variance in banana plug diameters.  I would suspect that most of my leads and cables have the lantern size and style of the Brymen's.  My expensive pomona and probemaster leads that I'll most likely be using anyway both have the larger lanterns.  Maybe UEi should do a little QC using other manufacturers leads? 

Thanks again for the quick support.       

P.S. Please give those new jack assemblies a vigorous workout with the Brymen leads before you ship them.

[EEVblog]

Thanks for the quick update Dave.  I'll be sending an email to get a replacement jack assembly from you as I'm pretty sure that my SN is within the affected range, though it's a shame that you've got to go through this. 

Just to make this clear, this is only for people with broken jacks. There is not a program to replace all jacks in that serial range, that's just the potential range of units from that jack manufacturing batch. UEi expect maybe a few dozen units to be affected tops.
So far I think we have about four units.

[EEVblog]

That was quick.

[Brumby]

We always knew you had the connections .....   

[dlow]

UPDATE:
The issue with the cracked input jacks is as several suspected, a molding issue.

input jacks which were injected from the uncompletely-cleared mould probably resulting in for ABS mixed with any foreign materials so the injected jacks could be more easily broken.

Units potentially affected are with serial numbers S/N 18087001 to 181008000
The sockets for these were manually inspected for this issue but it seems that some slipped passed the inspection and have resulted in cracking.

They also mention the Brymen leads are not ideal:

2. Our input jacks were designed to be ideally matched with our test lead probe with 4.2 - 4.3 phi.  However, Brymen's probe has 4.5 - 5.0 phi, which can give more mechanical stresses to our input jacks.

"Phi" means diameter of the banana plug.
I'm not sure about their measurements because I measured the Brymen at 4.3mm or a smidge over. The UEi ones are spot on 4mm and not the lantern type ones the Brymen use.
They aren't saying don't use the Brymen leads, just that could be a contributing factor in this case. Welectron have been supplying Brymen leads.
My new stock of meters will all come with UEi leads.

They will be sending me a bunch of replacement jacks so I can send to people who want that option.
If you have been affected by this and prefer to replace it yourself, please email me your address so I can send you one. Use the email Title "121GW Connector"
Alternatively you send your meter back to UEi at this address. I'm not sure if they will rework or replace the meter or board.

Attn: (Mr.) Heegoo Kang
Tel: 82-32-837-5777
309, A-dong, Smart Valley,
Songdomirae-ro 30, Yeonsu-gu, Incheon,
21990, Korea

Email sent. Thanks Dave!

[BillB]

Jack assembly replacement complete!

The new jacks easily accommodated the Brymen plugs without issue.

Thanks for the quick turn-around Dave!

[Axk]

Strange glitch with the switch, lightly pushing on the switch rebooted / turned on the multimeter. Not reproducible anymore. Moisture, contamination?

https://youtu.be/XtrQb5BGNpc

[CDaniel]

And repaired itself ? Interestingly . Maybe your switch wasn't correctly settled.

[EEVblog]

UPDATE:
UEi have indicated they have fixed (or greatly improved) the resistance drift problem.
They are just working on another issue that could take another week or two before a new firmware release.

[e0ne199]

UPDATE:
UEi have indicated they have fixed (or greatly improved) the resistance drift problem.
They are just working on another issue that could take another week or two before a new firmware release.

how about the bug on bar graph display whose range cannot be changed when switching to VA mode?? are they fixing that too?

[n3mmr]

UPDATE:
UEi have indicated they have fixed (or greatly improved) the resistance drift problem.
They are just working on another issue that could take another week or two before a new firmware release.

People have been talking about problems when long term logging to the SD-card.
Is that problem being addressed as well?

[jancumps]

UPDATE:
UEi have indicated they have fixed (or greatly improved) the resistance drift problem.
They are just working on another issue that could take another week or two before a new firmware release.

People have been talking about problems when long term logging to the SD-card.
Is that problem being addressed as well?

Yes

[joeqsmith]

UPDATE:
UEi have indicated they have fixed (or greatly improved) the resistance drift problem.
They are just working on another issue that could take another week or two before a new firmware release.

Is this the drift I asked about during your 10ohm speed test video or is there another problem with the resistance drift? 
https://www.eevblog.com/forum/testgear/eevblog-121gw-discussion-thread/msg2793590/#msg2793590

Is the other issue they are planning to go after the one where the auto range seems to not work with a biased HV AC source? 

[EEVblog]

Is this the drift I asked about during your 10ohm speed test video or is there another problem with the resistance drift? 

No, it's the 1Mohm range settling thing.

Is the other issue they are planning to go after the one where the auto range seems to not work with a biased HV AC source?

Yes.

[joeqsmith]

Is this the drift I asked about during your 10ohm speed test video or is there another problem with the resistance drift? 

No, it's the 1Mohm range settling thing.

Please provide a link to the description.  I went back about 10 pages and did not find any reference to it.   

[CDaniel]

This is a bit too much input ADC filtration and the charging effect is visible ... but the issue is the lack of filtration on lower ranges that makes readings jump when you put the hands near the probes/meter .
In fact 5M range is the least sensitive to noise , I hope they don't ruin it again 
A bit of charging / settling time is more acceptable that to have the reading jump all over the place ... the right ballance should have been sorted out long before production ...

[Axk]

Trying to measure a calculator's consumption in the uVA mode. The voltage on the secondary display is jumping between 1.5 and 0 with a regular frequency. The VA value is steady. The setup was not very sturdy but I think I held everything steady. Probably my mistake, not sure what I did wrong.
Am I supposed to be measuring the current on the low end?

https://youtu.be/1WAYKX1o5PU

https://youtu.be/WdhwUBUQrKs