D.E.V.I.C.E. is an encyclopedia of terms used by manufacturers of test and measurement equipment. T&M Atlantic created this service to better explain the functionality of instruments it offers, and to highlight the latest developments in the world of measurement equipment. We are using such tools as animation to bring words and pictures to life and to create not just an understanding but also an appreciation for technology that goes into the design of every instrument.
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On May 13, 1825, Leopoldo Nobili demonstrated the first astatic galvanometer, a historical instrument that measures electric current.
It consists of two magnetized needles, suspended from their centers by a long thin fiber which can turn freely. One needle is inside a coil of wire. When electric current passes through the coil, its magnetic field causes the needle to turn from its equilibrium position perpendicular to the coil to be parallel to the coil's axis. The second needle (visible), located above the coil and magnetized in the opposite direction, serves to cancel out the effect of the Earth's magnetic field (that's what the "astatic" means), and also serve as a pointer to indicate the magnitude of the current.