Products > Test Equipment
BM786 Switch Issue
<< < (6/15) > >>
joeqsmith:
All of the meters I looked at had these scratches in the switch area.  I didn't ask them about it.  Agree that it looks poor but it didn't seem to have much of an effect on the meter I life cycled.   If you watch that video, the meter was still working fine after that test.   Many meters that started out with smooth boards were ground to dust....

Here are a couple of pictures showing this area before I subject it to some high voltage with the meter set to ohms. 
bdunham7:
I don't know if it has been mentioned before, but it looks like your picture is missing the same chunk off the end of the trace as the other meter that failed?
floobydust:
There's nothing physically wrong with that PCB portion - it's just bad PCB CADD layout.
You have rectangular-ended switch polygons, rounded-end traces and soldermask connecting there, so it looks wonky.

Many traces exiting the rotary switch leafs are done wrong - they should exit radially. Otherwise you get overlap and extra scuffs. It's not a great switch PCB layout IMHO.

From the way the DMM cuts out when the switch is wiggled on Ohms, I suspect power being shorted out vs open circuit?

P.S. I wonder if you can even do this switch design in Altium, or you have to draw it in AutoCAD and import the switch portion?
joeqsmith:

--- Quote from: bdunham7 on March 27, 2021, 01:15:28 am ---I don't know if it has been mentioned before, but it looks like your picture is missing the same chunk off the end of the trace as the other meter that failed?

--- End quote ---

Interesting is that it would seem that this area of concern for you may actually be a way to improve the design of meters.  Consider the attached picture showing the BM786 after completing a 50,000 cycle life test on the switch.  Not Dave Jones 50K but full CW/CCW making one cycle.  Or 100,000 DJ cycles.   Notice in cases where the mask is removed in area around the contact's leading edge, we see some rounding off where in this case, we start with a smoother transition and less wear.   

Even with scratches the meter held up very good to this test compared with others I have looked at.  Low quality meters are ground to dust and if we want to talk about poor layouts that actually hurt the performance, lets at least mention the end results of placing a via in the center of the switch contacts.   
AVGresponding:

--- Quote from: joeqsmith on March 27, 2021, 12:41:49 am ---All of the meters I looked at had these scratches in the switch area.  I didn't ask them about it.  Agree that it looks poor but it didn't seem to have much of an effect on the meter I life cycled.   If you watch that video, the meter was still working fine after that test.   Many meters that started out with smooth boards were ground to dust....
--- End quote ---

Granted it probably doesn't affect switch life noticeably, but it does indicate a degree of hand finishing which is as we all know something you prefer to avoid due to cost, variability of results etc.

Can't be good for the solder mask, and there has to be at least a small risk of pinging off a component or damaging a trace.

It begs the questions, why do Brymen consider it necessary? What problem with the automated fabrication process is this an attempt to remediate?
Navigation
Message Index
Next page
Previous page
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod