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John Wiltrout's Blog Cheap Chinese Volt Amp Panel Meter won't zero
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  • Author Author: jw0752
  • Date Created: 9 Feb 2020 6:34 AM Date Created
  • Views 7828 views
  • Likes 11 likes
  • Comments 13 comments
  • zero fix
  • panel meter
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Cheap Chinese Volt Amp Panel Meter won't zero

jw0752
jw0752
9 Feb 2020

image

 

A while back I bought 8 of these small 0 to 30 Volt 0 to 10 Amp panel meters from China. I like to use them in my builds because they have in the past worked well for my needs and they are very inexpensive. The other day when I needed one for a new project I found the 4 of the 8 would not zero on the Amp Scale. They would say 2, 3, or 4 in the least significant position and this number would add to the actual current that the meter was attempting to read. This put the meter outside the small trimmers range to calibrate. Further the trimmer had no affect on the meter's 0 level display. I can accept some inaccuracy from these inexpensive meters but I knew I could not tolerate a meter that had a reading when it should have read zero.

 

I mention this problem in case anyone else has purchased these meters too. Here is what the board side looks like:

 

imageimage

 

I have devised a patch fix to the board that clears the problem and allows the regular I ADJ trimmer to do its job.

 

I will be glad to share the patch but only if someone has some of these with the same problem. Let me know if you have had a similar problem and I will continue the blog.

 

John

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Top Comments

  • kmikemoo
    kmikemoo over 5 years ago +5
    jw0752 I have purchased a few of these and, like shabaz , just had low expectations of accuracy. Personally, I'm super impressed that you figured out how to make the adjustment trimmer do what it's supposed…
  • ralphjy
    ralphjy over 5 years ago +5
    Hi John, I've been thinking of trying one of these meters but they don't have much documentation so it's interesting to see your experiences. Have you seen the schematic that was reversed engineered by…
  • jw0752
    jw0752 over 5 years ago in reply to clem57 +4
    Hi Clem, It is a hardware resistive trimmer. I will post about it later today since there was some interest. Since I am just a technician there may be some side effects that I am not aware of. A lot of…
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  • mrh586
    mrh586 over 3 years ago

    Hi

    My voltmeter turns on but only shows zero
    I reset but it didn't work

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  • mrh586
    mrh586 over 3 years ago

    Hi

    My voltmeter turns on but only shows zero
    I reset but it didn't work

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