Author Topic: EEVBlog 121GW Discussion thread  (Read 94485 times)

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Offline Diosol

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Re: EEVBlog 121GW Discussion thread
« Reply #325 on: February 09, 2018, 10:17:53 am »


I also made a quickie of 121GW. Dave's second video got me interested inspecting what happens while measuring resistance with multiple meters.
Fluke 322 clamp meter works a little bit differently and other meters went haywire. Switching lead polarity solved that issue.
Some day I'll do inspection of the voltages while measuring resistance and take a look does the Fluke 322 have reverse polarity.

Insulation tester had the highest current of 1,00 mA and maybe that's why it showed 1,4 MOhms in baseline setup.
 

Offline joeqsmith

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Re: EEVBlog 121GW Discussion thread
« Reply #326 on: February 14, 2018, 10:20:39 am »
I saw your test fixture and it looks pretty good.   I assume printed.  If you wanted to replicate the tests I have been running,  the switch is fully rotated both directions to complete one cycle.  I cycle them 50,000 times in 60 hours while measuring the contact resistance.  If the resistance gets about 1K for 1000 cycles in a row, I abort the test.  Other than that, I just let the run.   Pictures before and after and document if the use any sort of lubrication on the contacts.  That's about it. 

If you don't plan to record the contact resistance, you may want to consider inspecting the contacts every 10,000 cycles like Brymen.

Looking forward to seeing what you decide to do and the end results. 
How electrically robust is your meter?? http://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 
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Offline EEVblog

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Re: EEVBlog 121GW Discussion thread
« Reply #327 on: February 14, 2018, 10:51:58 am »
 
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Offline joeqsmith

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Re: EEVBlog 121GW Discussion thread
« Reply #328 on: February 14, 2018, 11:18:01 am »
First, thanks for taking the time to run this test.  Second, thanks for posting how you are running it and the results.  I have been curious if the pads had changed at all.   

Five minutes in, I switched to 1080.   Your 50K cycles would be a half for Brymen and what I am doing but still, what is up with this meter?   There is no way I would have expected to see these results after sending you those original pictures.    Impressive indeed. 

I could try and repeat it assuming the contacts are the same but it's not really going to prove anything.   Thanks again and looking forward to seeing the production parts ran.   
How electrically robust is your meter?? http://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 

Offline EEVblog

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Re: EEVBlog 121GW Discussion thread
« Reply #329 on: February 14, 2018, 11:29:08 am »
Five minutes in, I switched to 1080.   Your 50K cycles would be a half for Brymen and what I am doing but still, what is up with this meter?   There is no way I would have expected to see these results after sending you those original pictures.    Impressive indeed. 

I expected worse too, but that's what we got.
I don't know what serial number I sent you, but it would have been around a similar date, so likely exactly the same switch and contacts.
 
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Offline joeqsmith

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Re: EEVBlog 121GW Discussion thread
« Reply #330 on: February 14, 2018, 01:00:18 pm »
Five minutes in, I switched to 1080.   Your 50K cycles would be a half for Brymen and what I am doing but still, what is up with this meter?   There is no way I would have expected to see these results after sending you those original pictures.    Impressive indeed. 

I expected worse too, but that's what we got.
I don't know what serial number I sent you, but it would have been around a similar date, so likely exactly the same switch and contacts.
If these were the production parts, I would like to try and understand why such a dramatic difference.  I wouldn't have guessed it had more than a thousand cycles on it but for all I know, UEI may have cycle tested it.   Looking back over the pictures, it appears the contacts are what was wearing.  Even looking at the last few that they sent, it looks like something was still going on.  Strange.   

Looking at the video and the large gap in the fingers that rotate the knob, are you sure you are getting the full stroke of the switch?  It looks like it may only rotate 90 degrees.  Still even it that was the case, I would have still expected that area to have a fair amount of wear.   

Just scratching my head. 

 

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

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Re: EEVBlog 121GW Discussion thread
« Reply #331 on: February 14, 2018, 02:55:39 pm »
Five minutes in, I switched to 1080.   Your 50K cycles would be a half for Brymen and what I am doing but still, what is up with this meter?   There is no way I would have expected to see these results after sending you those original pictures.    Impressive indeed. 

I expected worse too, but that's what we got.
I don't know what serial number I sent you, but it would have been around a similar date, so likely exactly the same switch and contacts.
If these were the production parts, I would like to try and understand why such a dramatic difference.  I wouldn't have guessed it had more than a thousand cycles on it but for all I know, UEI may have cycle tested it.   Looking back over the pictures, it appears the contacts are what was wearing.  Even looking at the last few that they sent, it looks like something was still going on.  Strange.   

Looking at the video and the large gap in the fingers that rotate the knob, are you sure you are getting the full stroke of the switch?  It looks like it may only rotate 90 degrees.  Still even it that was the case, I would have still expected that area to have a fair amount of wear.   

Just scratching my head.

I’ll add to the head scratching. Or let’s just say thinking out loud.
I agree with Joes counting as this is only a half cycles since a user will turn on, then off and that’s a full cycle. Just like they charging cycles on a battery, charge and discharge for a full cycle.

My questions thinking out loud would be around the way the PLA adapter is mounted to the stepper motor. Seems to me and knowing PLA (it looks like PLA) the part will wear some and if a set screw was used the adapter on the motor will start to slip. I’m not a big fan of PLA for mechanical use from personal experience when I first started doing 3D printing.

Maybe something a little stronger on the adapter with something that also has a little flex like a nylon mix filament. The nylon will allow a little flex without breaking the part, and you can over turn the switch just a little past the off positions. My thinking is most people always turn past the off point, they only let go of the switch because the switch stopped them. I’m not talking crazy over shoot on the switch with massive torque, just a little to replicate real human usage. If you set the controller to over shoot with a PLA part even if it’s made with 100% fill, it will start to stress crack, break, or give away on the tolerances of the whole for the set screw and slip.

But I guess that’s why I’m wondering how the part is held into the stepper motor?
It’s a nice rig, but just might benefit from a few little tweaks?
Scott
« Last Edit: February 14, 2018, 05:21:27 pm by Scottjd »
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Offline 1anX

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Re: EEVBlog 121GW Discussion thread
« Reply #332 on: February 14, 2018, 03:16:51 pm »

I agree with Joes counting as this is only a half cycles since a user will turn on, then off and that’s a full cycle. Just like they cling cycles on a battery, charge and discharge for a full cycle.

Hmmm, I disagree with your observation in regards to the operation of this meter!

There is an OFF position at each end of the selector, so in effect a user could easily select a range and then switch OFF by continuing in the same direction. Hence one cycle of the switch is achieved by rotating in one direction.

Regardless of how you view the definition of one cycle, at the very least we now have a measured number of cycles to interpret contact wear!

Its interesting, but of course it needs to be repeated with a production unit which I'm sure will happen just as soon as UEi provide one.
« Last Edit: February 14, 2018, 03:20:41 pm by 1anX »
 

Offline EEVblog

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Re: EEVBlog 121GW Discussion thread
« Reply #333 on: February 14, 2018, 04:12:39 pm »
My questions thinking out loud would be around the way the PLA adapter is mounted to the stepper motor. Seems to me and knowing PLA (it looks like PLA) the part will wear some and if a set screw was used the adapter on the motor will start to slip.

It's not slipping.
That meter did 50,000 genuine rotations.
« Last Edit: February 14, 2018, 04:15:08 pm by EEVblog »
 

Offline Scottjd

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Re: EEVBlog 121GW Discussion thread
« Reply #334 on: February 14, 2018, 05:15:22 pm »

I agree with Joes counting as this is only a half cycles since a user will turn on, then off and that’s a full cycle. Just like they cling cycles on a battery, charge and discharge for a full cycle.

Hmmm, I disagree with your observation in regards to the operation of this meter!
There is an OFF position at each end of the selector, so in effect a user could easily select a range and then switch OFF by continuing in the same direction. Hence one cycle of the switch is achieved by rotating in one direction.
I see your point. But at the same time I think most users will always go for the same “off” position. Maybe based on if they use the meter mostly for current readings, or voltage readings. With mode selected aside I’m still thinking most people will always go to the left off position if they own more then one meter just based on muscle memory and the fact the most other meters they own also go off to the left.

For me personally I will always turn it off to the left because I’m used to turning my meters off to this direction. I do own one meter that has a dual off just like the 121GW (Digitek DT-4000ZC) and it always goes off to the left. Even if I use a mode on the right side of the range switch it still gets turned off to the left. If I had bought a meter that only turned off to the right and didn’t have a left off option, this would probably annoy me to the point of returning it.

But as you said, either way 25K, or 50K is still a lot of switching, and at least it’s getting tested now before being put back into manufacturing and sold to more people.
So what is that saying, “Better late then never”.
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Offline Brumby

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Re: EEVBlog 121GW Discussion thread
« Reply #335 on: February 14, 2018, 06:09:21 pm »
For me personally I will always turn it off to the left because I’m used to turning my meters off to this direction. I do own one meter that has a dual off just like the 121GW (Digitek DT-4000ZC) and it always goes off to the left. Even if I use a mode on the right side of the range switch it still gets turned off to the left. If I had bought a meter that only turned off to the right and didn’t have a left off option, this would probably annoy me to the point of returning it.

Same.
 

Offline EEVblog

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Re: EEVBlog 121GW Discussion thread
« Reply #336 on: February 14, 2018, 06:50:22 pm »
Now I need to know if there is or has ever been such a meter?

Near enough

« Last Edit: February 14, 2018, 09:39:50 pm by EEVblog »
 

Online HKJ

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Re: EEVBlog 121GW Discussion thread
« Reply #337 on: February 14, 2018, 07:06:47 pm »
For me personally I will always turn it off to the left because I’m used to turning my meters off to this direction. I do own one meter that has a dual off just like the 121GW (Digitek DT-4000ZC) and it always goes off to the left. Even if I use a mode on the right side of the range switch it still gets turned off to the left. If I had bought a meter that only turned off to the right and didn’t have a left off option, this would probably annoy me to the point of returning it.
Same.

Now I need to know if there is or has ever been such a meter?


I have not seen that, but some meters has off at the center.

 

Online Hydron

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Re: EEVBlog 121GW Discussion thread
« Reply #338 on: February 14, 2018, 08:03:16 pm »
Megger annoyingly do the middle-OFF thing too, but ugh, I think that meter above would win a prize in several "worst meter" categories.
 

Offline 1anX

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Re: EEVBlog 121GW Discussion thread
« Reply #339 on: February 14, 2018, 08:20:14 pm »
 

Offline joeqsmith

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Re: EEVBlog 121GW Discussion thread
« Reply #340 on: February 14, 2018, 08:22:48 pm »
I am not concerned with how you define a cycle, people just need to be aware if they want to compare results that it half of what I run them to.  Still, at 25K, it's close to what Brymen tests to.   

For the meters having a separate on/off switch, I just fully rotate the knob. 

I have attached a few pictures to provide a contrast of what I saw with SN# 814.  Just be clear, I never cycled this meter beyond normal use prior to taking these pictures.   

Have you checked to make sure you were getting a full cycle with that coupler?  At 1:00 min in, note that the meter was only turning off in the CCW direction.
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Offline joeqsmith

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Re: EEVBlog 121GW Discussion thread
« Reply #341 on: February 14, 2018, 08:24:03 pm »
Zoomed in.
How electrically robust is your meter?? http://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 

Offline joeqsmith

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Re: EEVBlog 121GW Discussion thread
« Reply #342 on: February 14, 2018, 08:35:42 pm »
SN#813a,b were taken from your video for a comparison.  The contact tips appear to have roughly the same amount of wear.  If your video had shown any metallic debris, I would not question it but this is just so different.
How electrically robust is your meter?? http://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 

Offline Brumby

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Re: EEVBlog 121GW Discussion thread
« Reply #343 on: February 14, 2018, 08:52:14 pm »
For me personally I will always turn it off to the left because I’m used to turning my meters off to this direction. I do own one meter that has a dual off just like the 121GW (Digitek DT-4000ZC) and it always goes off to the left. Even if I use a mode on the right side of the range switch it still gets turned off to the left. If I had bought a meter that only turned off to the right and didn’t have a left off option, this would probably annoy me to the point of returning it.
Same.

Now I need to know if there is or has ever been such a meter?

I picked up two of these from the "crap bin" at Jaycar many years ago.  They had problems with the rotary switch.  One I was able to sort out and it has been pretty reliable.  The other was not so inclined - and is buried somewhere.




(Sorry about the transistor tester)
« Last Edit: February 14, 2018, 08:55:58 pm by Brumby »
 

Offline Scottjd

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Re: EEVBlog 121GW Discussion thread
« Reply #344 on: February 14, 2018, 09:41:55 pm »
I have not seen that, but some meters has off at the center.
Do clamp meters count?  Well I have both (left and right), left, top (up), bottom (down), and push button. I can’t find my greenlee meter and I used to have a southwire, but I gave it away. I had to check my old BM235 review video to see what that one was. Now I also wish I never gave away my first RadioShack meter I bought when I was a kid.
But I still didn’t realize until tonight I had this many, and I left out the other 3 harbor freight free meters that are just basically battery testers.
Most of them were given to me, one was found, one was $1 yard sale buy, and the others I bought. One more still on the way that I’m waiting on. I think I have a multimeter problem. But surprisingly no right off switch meters. Even the bottom meters have the power button on the left side.
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Offline EEVblog

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Re: EEVBlog 121GW Discussion thread
« Reply #345 on: February 14, 2018, 09:50:32 pm »
Have you checked to make sure you were getting a full cycle with that coupler?

Yes.
 

Offline joeqsmith

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Re: EEVBlog 121GW Discussion thread
« Reply #346 on: February 15, 2018, 05:08:07 am »
Have you checked to make sure you were getting a full cycle with that coupler?

Yes.
Strange that the meter only turns off in the CCW direction and never in the CW.  I tried turning mine this fast and it seems to cycle the power no matter how fast I cycle it by hand.   

Makes sense that the beeper would not sound as fast as it is being cycled. 

I read through the YT comments and noticed a few about the possible concern with heat buildup.  I doubt you would see a problem with the speed you are running at. 
How electrically robust is your meter?? http://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 

Offline ChrisG

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Re: EEVBlog 121GW Discussion thread
« Reply #347 on: February 15, 2018, 05:56:45 am »
I'm puzzled now that with my 121GW which I use 2-3 times a week for let's say 20-25 cycles I had gunk, abrasion or wear after a couple of weeks already. Perhaps I should clean it now and then take picture and re-take after a month or so. Btw when switching to Ohms range I have to depress the selector switch in order for the meter to switch on otherwise it beeps and then goes dark.
 

Offline 1anX

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Re: EEVBlog 121GW Discussion thread
« Reply #348 on: February 15, 2018, 07:59:24 am »
I'm puzzled now that with my 121GW which I use 2-3 times a week for let's say 20-25 cycles I had gunk, abrasion or wear after a couple of weeks already. Perhaps I should clean it now and then take picture and re-take after a month or so. Btw when switching to Ohms range I have to depress the selector switch in order for the meter to switch on otherwise it beeps and then goes dark.
Sounds like a good idea to me, take pictures now with cleaned contacts and again later to compare.
Probably a waste of time though, if you consider that you will be receiving new contacts and selector switch in the near future?
 

Offline joeqsmith

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Re: EEVBlog 121GW Discussion thread
« Reply #349 on: February 16, 2018, 01:28:57 pm »
I'm puzzled now that with my 121GW which I use 2-3 times a week for let's say 20-25 cycles I had gunk, abrasion or wear after a couple of weeks already. Perhaps I should clean it now and then take picture and re-take after a month or so. Btw when switching to Ohms range I have to depress the selector switch in order for the meter to switch on otherwise it beeps and then goes dark.

Please don't clean it or even take it apart.  Just keep using it until you get your replacement parts.  Then take some new pictures so we can get some feel for how the wear was progressing, if at all. 

I can't tell you why the one in Dave's video looks so clean when it appears to have a fair amount of wear on the wiper contacts.  That copper can't just magically disappear.  Regardless, it's not production parts so we really can't use the data except to scratch our heads and be puzzled.    Looking forward to seeing the production  parts, with the resistance and maybe run 50,000 full strokes.    The benefit of seeing this test ran is eventually I will repeat it and the results should be the same.   
How electrically robust is your meter?? http://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 


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