Definition - What does Galvanometer mean?
A Galvanometer is an electromechanical device which is very sensitive to electrical current. A small amount of current passing through its coil can deflect the galvanometer needle. The primary purpose of a galvanometer is to detect the electrical current passing through an electrical circuit and measure the amount of current flowing in an electrical circuit. However, it is not meant to measure heavy currents.
Petropedia explains Galvanometer
A galvanometer works on the principle of converting electrical energy into mechanical energy. It is very sensitive and can detect the currents of very small magnitude say 10-9amperes. This is why it is also sometimes called as a sensitive ammeter. It only gives the deflection equivalent to the amount of current flowing through it, but of small magnitude. Based on the deflection on a measurement scale located in the front face of the galvanometer, the user can note down the electrical current flowing through the circuit.
The most commonly used galvanometer is the moving coil galvanometer that consists of a permanent magnet through which a coil of wire is pivoted. This coil is attached to the thin pointer that traverses the calibrated scale. A magnetic field is generated whenever current flows through the coil. This magnetic field acts against the magnetic field of the magnet which induces an electromagnetic force or EMF. This EMF twists the coil, pushing against the spring, and moves the pointer. This pointer points the reading at the calibrated scale and a user can note down this reading.