Ammeter dial. Dial of an old ammeter designed to measure the amount of electrical current, in amps (amperes), passing through a wire. The ampere is named after the French physicist Andre Ampere (1775-1836). This ammeter can measure between 0 and 10 amps. Early ammeters used analogue dials like this. They were based on modified galvanometers. A galvanometer measures an electrical current by the deflection produced by its magnetic effects. The deflection, proportional to the amount of current, moves the pointer and so produces the reading. The first dial galvanometers date from the 1880s.