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UNI-T UT61E Multimeter teardown photos.

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joeqsmith:
Do you feel sprinkling in a few parts will make it more safe or robust?  If you do and in fact it has no effect then that in of itself would make it less safe.   How will you know if there is an improvement?


--- Quote from: hgg on May 14, 2016, 03:30:20 pm ---I have ordered two of these :

In what circumstances adding these MOVs will make the multimeter less safe?

--- End quote ---

hgg:

--- Quote --- How will you know if there is an improvement?
--- End quote ---

I guess you would not know and you'd better not find out the hard way.
I will send it to you to throw some kVs and see what happens...   :)

But seriously, if there is a transient and the MOVs are working, wouldn't they clamp it down
safely?   Before them there are two PTCs as well. 

joeqsmith:
I don't know about the safety side at all.   I just don't throw that sort of energy at them.  People recommending to add parts should have some data based on fact.   I gave up on Santa Claus and the Tooth Fairy years ago.   

The 181A fully populated with all of it's fancy protection failed with just one hit of a very low ESD event.  Had they removed the parts and saved that money, it would have failed just the same..   On the flip side, had I received the meter without the protection circuitry populated and then correctly guessed what the parts were and added them, it would have still failed.  :-DD   The layout is important and can't be ignored. 

What you have suggested may not be a bad idea.  If we forget about safety, I could run your meter to see if there was an improvement in robustness but you may not like the end results.   What's that meter cost?  When I made changes to the UT181A, I could have just said I fixed it or just reapplied a single ESD transient and left it at that.   I thought it was better to throw everything I could at it and leave no question the meter's robustness had indeed been improved.
 

--- Quote from: hgg on May 14, 2016, 03:50:00 pm ---
--- Quote --- How will you know if there is an improvement?
--- End quote ---

I guess you would not know and you'd better not find out the hard way.
I will send it to you to throw some kVs and see what happens...   :)

But seriously, if there is a transient and the MOVs are working, wouldn't they clamp it down
safely?   Before them there are two PTCs as well. 

--- End quote ---

hgg:
Do you have the specs of the UT181a MOVs it came with?

joeqsmith:
Yes.  It was all covered in that second half of the video starting about 8 minutes into it.   


--- Quote from: hgg on May 14, 2016, 04:37:08 pm ---Do you have the specs of the UT181a MOVs it came with?

--- End quote ---


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