Editing Multimeter (section)

=== Precursors ===
The first moving-pointer current-detecting device was the [[galvanometer]] in 1820. These were used to measure resistance and voltage by using a [[Wheatstone bridge]], and comparing the unknown quantity to a reference voltage or resistance. While useful in the lab, the devices were very slow and impractical in the field. These galvanometers were bulky and delicate.

The [[D'Arsonval galvanometer|D'Arsonval–Weston]] meter movement uses a moving coil which carries a pointer and rotates on pivots or a taut band ligament. The coil rotates in a permanent magnetic field and is restrained by fine spiral springs which also serve to carry current into the moving coil. It gives proportional measurement rather than just detection, and deflection is independent of the orientation of the meter. Instead of balancing a bridge, values could be directly read off the instrument's scale, which made measurement quick and easy.

The basic moving coil meter is suitable only for direct current measurements, usually in the range of 10&nbsp;μA to 100&nbsp;mA. It is easily adapted to read heavier currents by using shunts (resistances in parallel with the basic movement) or to read voltage using series resistances known as multipliers. To read alternating currents or voltages, a rectifier is needed. One of the earliest suitable rectifiers was the copper oxide rectifier developed and manufactured by Union Switch & Signal Company, Swissvale, Pennsylvania, later part of Westinghouse Brake and Signal Company, from 1927.<ref>"A New Electronic Rectifier", L.O Grondahl & P.H. Geiger, Transactions, American Institution of Electrical Engineers, February 1927 pp. 358–366</ref>