On 2015-10-10, ehsjr wrote:

For what they are, it's really not too bad. 4 meters - $1.50 per
meter - with maybe +/- 3.3% error each. At that low cost, they
undoubtedly were not "factory calibrated". So if you wanted to take
the time and effort, you might be able to spin a pot and file
(or add solder to) a shunt to get better accuracy.

Thanks for suggesting that. Close inspection of the rear of he meters
revealed tiny open-frame preset pots for both voltage and current trim.
The meters now agree with my cheap multimeters, and with each other.

The pots seem fairly crummy though, I'm not sure that they will stay
set.

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\_(ツ)_