The main function of a galvanometer is used to measure the presence of a small amount of current flowing in a circuit.
Current in the circuit is directly proportional to reflection of a moving coil.
It deflects as an electrical current travels through the coil. The galvanometer is a very sensitive device. For a small current of few microamperes, the galvanometer deflection will be maximum.
The galvanometer can be used to measure:
The value of current in the circuit by connecting it in parallel to low resistance.
The voltage by connecting it in series with high resistance.