The sensitivity of an ammeter is an expression of:

The sensitivity of an ammeter is defined by the amount of current required to move the meter's needle to its maximum reading, which is known as full-scale deflection. A more sensitive ammeter requires a smaller amount of current to reach this full-scale mark. This differs from voltmeter sensitivity, which is typically expressed in ohms per volt. While both concepts ultimately relate to the characteristics of the moving-coil mechanism, an ammeter's sensitivity is strictly an expression of its full-scale deflection current.