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:
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.