Galvanometer with Astatic Needle Pair
Self-made by a researcher, around 1830

In 1820, Hans Christian Ørsted described the deflection of a magnetized needle caused by an electric current. This effect can be used to measure electrical currents. Two oppositely poled needles counteract the disturbing influence of the Earth’s magnetic field, thus the name astatic needle pair. This example is an instrument built for laboratory purposes; the serial production of galvanometers first began in the 1870s.

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