EEVblog 121GW Multimeter Issues

[exe]

Somebody already posted a python script that decodes calibration data. I think the decoded data showed just a two-point calibration, no fancy "ADC curvature compensation" or anything else sophisticated. So, as far as I remember, it's perfectly possible to use original calibration data in custom firmware.

[firewalker]

And someone posted code that can write to the screen.

https://github.com/tpwrules/

Alexander.

[Axk]

What conditions the Hz mode is intended for?

I've not found any details in the manual.
It must be a standard thing with multimeters I suppose.

I've tried measuring a 3.3V 50MHz oscillator's output and a 5V 16MHz ctystal (arduion) and the display stayed at all 0s in both cases.

What signals is it supposed to measure in the Hz mode?

[Axk]

Now I see the manual saying sensitivity > 2.5V RMS.
Does it mean that a square wave has to be at least 5V (with a 50% duty cycle) for it to sense it?
So I suppose it is not intended for measuring digital signals then (as these are mostly 3.3V or below nowadays)?
What would the 999 KHz range be useful for then?

[CDaniel]

It is good for 3,3V logic , but not at 50MHz 
That rms value should be for sine wave , but is more sensitive anyway . The amplitude is important for digital signal , otherwise low duty-cycle PWM wouldn't be measurable as the rms is very small .

[Axk]

  My bad, misread the numbers. 999KHz, so it's up to 1 MHz...

[dlow]

The plastic ring on my volt-ohm jack seems to have broke somehow during normal use. The protective ring came out when I removed the probe. Is there some way to get a replacement jack or have it repaired?

[BillB]

1) Purchased. 
2) Plugged in leads that came with the meter. 
3) Ran through basic measurements to make sure it worked. 
4) Removed leads - everything OK.
5) Plugged in leads, coiled around meter, probes pressed into holster.
6) Put on shelf.
7) A few weeks later,decide to store leads by hanging them.
8 ) Remove leads, shroud sticking out of lead banana plug. 

I haven't even opened up the meter to update the firmware yet.

I've snapped a few close ups of the broken shroud.  It is seriously stress cracked beyond what I would think the mere insertion and removal of test leads should cause. 

So, how can I fix this?  Superglue? 

[BillB]

Thinking that perhaps I was too rough or something on the V jack, I started looking at the others.  I used the mA once to verify operation with the provided leads (I may have used the A jack once as well).  Both mA and A shrouds are already cracked near the top around near the edge of the metal insert.  The attached image shows that the mA shroud already cracked (just not completely broken through).

The common shroud appears to still be intact.
 

[darik]

I strongly suspect these cracks are somehow happening during manufacture. I just don't see how you could put the right kind of forces on one of those things to break it that way once it's in the meter. I think some are shipping with cracks but nothing gets noticed until they break right off.

I can't remember for sure, but IIRC it's always red ones that break. Bad batch of components maybe? Everyone should probably check theirs. Mine seems fine but it's one of the early ones, seems like it's the more recent ones doing it.

Thinking that perhaps I was too rough or something on the V jack, I started looking at the others.  I used the mA once to verify operation with the provided leads (I may have used the A jack once as well).  Both mA and A shrouds are already cracked near the top around near the edge of the metal insert.  The attached image shows that the mA shroud already cracked (just not completely broken through).

The common shroud appears to still be intact.
 

[beanflying]

1) Purchased. 
2) Plugged in leads that came with the meter. 
3) Ran through basic measurements to make sure it worked. 
4) Removed leads - everything OK.
5) Plugged in leads, coiled around meter, probes pressed into holster.
6) Put on shelf.
7) A few weeks later,decide to store leads by hanging them.
8 ) Remove leads, shroud sticking out of lead banana plug. 

I haven't even opened up the meter to update the firmware yet.

I've snapped a few close ups of the broken shroud.  It is seriously stress cracked beyond what I would think the mere insertion and removal of test leads should cause. 

So, how can I fix this?  Superglue? 

Look at the plugs carefully that they were not the cause first! If you have some verniers do some measuring of them and inspection of the lantern and outer shroud.

Superglue even with an activator will generally not give you a good bond between the parts in spite of it sticking. Most likely it will re crack at the same point. Depending on the plastic used an appropriate solvent cement might work but that may cause issues with tolerances.

Best bet is drop Dave or whoever you brought the meter from first and email and look at getting replacements.

Undershot injection molded parts do happen but you would need some better shots to really look at the entire edge of the fracture and surrounds to try and figure out what caused it if not the jacks 

[EEVblog]

So, how can I fix this?  Superglue? 

I wouldn't think superglue would work for something like this, probably more of  two part epoxy thing maybe?
I've contacted UEi to see what the deal is.
It seems to have happened in a couple of cases now, and given the numbers shipped and the use they've had it's unlikely to be a systemic issue.

[BillB]

Look at the plugs carefully that they were not the cause first! If you have some verniers do some measuring of them and inspection of the lantern and outer shroud.

Well, I couldn't measure the lanterns without taking off the shrouds, but did measure the outer shrouds and they were roughly the same at 6.50mm ID 8.00mm OD.  Peeking down inside the lanterns on both they looked roughly the same diameter.  The lanterns on the probe ends were roughly 4.65mm and were significantly more difficult to insert into the common jack than the shrouded ends, so I assume that the shrouded lanterns were narrower.  The inside diameter of all the jack shrouds is the same at ~4mm.

Inserting both shrouded ends into the common jack wasn't difficult and didn't cause any damage to the black shroud.  Plugging the shrouded ended into other equipment wasn't difficult and didn't cause any damage.

Given this, I don't believe the probe shrouded plugs are the problem.
 

[BillB]

I wouldn't think superglue would work for something like this, probably more of  two part epoxy thing maybe?
I've contacted UEi to see what the deal is.
It seems to have happened in a couple of cases now, and given the numbers shipped and the use they've had it's unlikely to be a systemic issue.

Thanks Dave.  I purchased this from your store, not because I needed yet another meter, but more to support the blog/channel.  Now that I've seen the extent of the cracking, I've abandoned the gluing idea.  I was just trying to avoid more round-the-world shipping.     

[EEVblog]

I wouldn't think superglue would work for something like this, probably more of  two part epoxy thing maybe?
I've contacted UEi to see what the deal is.
It seems to have happened in a couple of cases now, and given the numbers shipped and the use they've had it's unlikely to be a systemic issue.

Thanks Dave.  I purchased this from your store, not because I needed yet another meter, but more to support the blog/channel.  Now that I've seen the extent of the cracking, I've abandoned the gluing idea.  I was just trying to avoid more round-the-world shipping.   

Thanks.
One problem with the UEi jacks is that they are an integral assembly, so a replacement would either be an entire assembled board, or replacing all 4 jacks in the soldered assembly, you can't just replace one.
I'm wiggling on one removed board fairly aggressively (once out of the case you can grasp the red jack protrusion with your fingers) and I can't make it budge, let alone feel like it's weakening.
Will see what UEi comes back with.
My guess would be a manufacturing defect of some sort. Given that it seems impossible to visually inspect these, it's likely that some outlier bell curves parts slip through.
If it was some sort of change in the molding or whatever then I'd expect a more systemic problem and a lot more to show up.

[floobydust]

It might be damage due to the metal insertion step over-forcing the plastic and causing fractures. If the metal is out of spec, it might be stressing the plastic.

[EEVblog]

It might be damage due to the metal insertion step over-forcing the plastic and causing fractures. If the metal is out of spec, it might be stressing the plastic.

I'd like to see the manufacturing process for that. It seems like the barrel is a separate mold and then inserted at some step.

[gnavigator1007]

I know that there had been some issues previously reported about defects with some of the Brymen leads, but it is interesting that future meters will be sold with uei leads. Dave, was this your call to simplify things or did uei recommend this change? BillB, what leads were you using when this happened? I know you said that they were the ones that came with the meter, but I recall talk of an option between the Brymen and uei leads that was a possibility at one point. Not sure if that happened or not.

[EEVblog]

I know that there had been some issues previously reported about defects with some of the Brymen leads, but it is interesting that future meters will be sold with uei leads. Dave, was this your call to simplify things or did uei recommend this change?

It was just to simplify things.
Before I had to order the Brymen leads separately, keep track of stock, and install in each box manually before shipping out. Also, there is sometimes supply lead time issues with the Brymen leads.
Much easier to just get UEi to supply their leads, about the same cost.
Any relation to this broken connector issue is entirely coincidental.

Yes there have been a few reports of broken tips on the Brymen leads in recent times, quality control is perhaps slipping there a bit, never used to get that.

[gnavigator1007]

Kind of figured. I've got quite a few sets of those and so far they've been problem free. From what I remember reading, the issues reported thus far had mostly been quality control problems on the stabby end.

[EEVblog]

Kind of figured. I've got quite a few sets of those and so far they've been problem free. From what I remember reading, the issues reported thus far had mostly been quality control problems on the stabby end.

Yes, I don't recall a single issue with the banana plug end.

[Muttley Snickers]

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.   

[EEVblog]

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 ?.

If it came from me then it would have been the Brymen ones, unless it's Welectron unit, and I'm not 100% sure what leads they supply but likely the Brymen ones as they also stock the Brymen leads.
I have not started shipping the new leads units yet.

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.

Yes, when we were doing the Kickstarter logistics, some units in the EU came with UEi leads.
I don't think I've ever shipped any from here.

[Scottjd]

Kind of figured. I've got quite a few sets of those and so far they've been problem free. From what I remember reading, the issues reported thus far had mostly been quality control problems on the stabby end.

Yes, I don't recall a single issue with the banana plug end.

I think I had a set of Brymen probes that one banana end was tight in most of my meters, and really tight in the 121GW KS they came with. You replaced them and all was good.
If the meter had any plastic shrouding issues with the first batch that one probe you replaced would have cracked it for sure.

[EEVblog]

Kind of figured. I've got quite a few sets of those and so far they've been problem free. From what I remember reading, the issues reported thus far had mostly been quality control problems on the stabby end.

Yes, I don't recall a single issue with the banana plug end.

I think I had a set of Brymen probes that one banana end was tight in most of my meters, and really tight in the 121GW KS they came with. You replaced them and all was good.
If the meter had any plastic shrouding issues with the first batch that one probe you replaced would have cracked it for sure.

Ah, that rings a bell.
BTW, Brymen don't make the leads, they just order them from another mystery OEM. But that would be the same for most manufacturers.