Handheld meter robustness testing

[joeqsmith]

Someone has asked about testing the 121GW again, suggesting that the rotary switch and input protection may have improved since the last time I looked at it late in 2019.   

Has anyone bought one in say the last 6 months that would be willing to pull it down and post some photos?  I would like to see the PCB thickness, shim if present, closeup of switch contacts, PCB any other areas of interest. 

[ploxiln]

I purchased a 121gw from Dave's online store back in September 2023, I think that's probably recent enough.

I struggled to get the range switch shaft clips off to get the board out ... damaged the plastic clips around the range switch shaft a tiny bit, not too bad, it'll be fine. There is no shim, as expected. The PCB is about 1.6 mm thick. Clamps are the latest version (I think there was a tiny daughter board on some older revisions).

[joeqsmith]

Thanks.

Interesting, they went back to a single dimple contact rather than the double dimple.  Plating appears the same.  I've seen them change these contacts over and over again.  I wonder why they can't settle on a design.  I take it you don't have a set of calipers to measure the PCB thickness.   If you lift off the switch contact holder from the brass hex shaft, is there a shim under it? 

PCB has some changes.  New clamp design.  I wonder why they changed it and it it improved its electrical robustness.  With it being Dave's meter, I am surprised he doesn't show off the changes and explain the reasons for them.   Maybe he did and I wasn't paying attention.   

***
Just an FYI, I had bought two of these to review.  Showing the board of the unit that was damaged during the grill starter.  Notice the changes. 

[ploxiln]

I do have a cheap digital caliper ... just not very experienced, and being a bit cautious/ginger - the reading depends a bit on how much pressure I apply to the jaws. It's probably actually 1.5 mm, that's what I get when applying more pressure.

I don't have a great setup for the close-ups, anyway, some more switch detail ...

[joeqsmith]

Measuring mine under the large HRC fuse where there is no copper I measure 1.40mm.  Measuring in that same are with copper on both sides, I measure 1.49mm.  The shim thickness on this meter measures 1.05mm.  Dave had said the shim was made to correct for the wrong thickness of the PCB.  I was expecting yours to measure over 2mm.   May have been a story? 

Shown is one of the double dimple wipers from my meter after the 50,000 (full rotation) life cycle test.

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Looking at your PCB, the switch contacts appear identical to mine.  I know my meter when set to the LowZ mode does not have enough spacing to prevent it from flashing over at the levels I typically test at.  Looking at this meter, it doesn't appear that I tried that with the higher energy generator as the PCB doesn't appear damaged.