The AMP meter is a new meter designed for battery testing and measurement, but it’s still not a universal device.
AMP meters measure voltage in amps, not volts.
For a 12V battery, the Ammeter volt meter measures about 8.8 volts per amp, so it’s not a very accurate unit for battery voltages.
The Ammeter voltage meter also only measures one voltage per amp at a time, so if the battery is overcharged, you’ll get different readings on the AMP and the battery voltage.
Here are a few tips to convert an 12V Ammeter into a meter that measures amps instead of volts.