How much amp draw does amp gauge versus volt meter?

A meter that you find in large distribution panels only receives part of the supply voltage. The volt meters have a full scale deflection of 5 volts. The amp meters have a full scale deflection of 5 amps. These meters are supplied from, for voltage, potential Transformers and for amperage, current transformers. The transformers are ratio driven so that the maximum input will always produce a 5 volt or 5 amp output.

The legend on the meter is matched to the transformers. For example, if the maximum current applied to a current transformer is 300 amps then the transformer ratio will be 60:1. So for every 60 amps the transformer detects the meter needle will move up to a position on the meter face equalling 60 amps. This is a linear movement all the way up to full scale deflection of 300 amps equalling 5 amps to the meter.