Properbly calibrate cheap Ebay Volt/Ammeter

[tobimai]

Hello,

I bought a cheap (8€) dual Volt/Amp meter on Ebay from China. If a adjust the pot on the back so that it shows 2V if it's supposed to show 2V. But If I then apply 12V it shows only 11V for example. Is there any way to properly calibrate it or is it just "Chinese accuracy"

Thanks
Tobi

[Kleinstein]

Usually there is just one adjustment for the scale factor. So looks like this unit has a problem - if 12 V is near the maximum, this could be a protection circuit.