The first galvanometer was built just months after Hans Christian Ørsted demonstrated in 1820 that an electric current can deflect a magnetized needle.
The device was assembled by German mathematician and physicist Johann Schweigger, who called it a multiplier.
A galvanometer consists of a needle attached to a coil mounted so that the coil is allowed to pivot freely within a magnetic field created by the poles of one or more permanent magnets.
When electricity is allowed to pass through the coil, the magnetic field generated by the current-carrying wire interacts with the field of the permanent magnets, generating a twisting force known as torque that rotates the coil. The deflection of the galvanometer’s needle is proportional to the current flowing through the coil.