Galvanometer Instruments
Many types of chart recorders use a galvanometer to drive the marking device. A light coil of wire suspended in teh magnetic field of a permanent magnet deflects in proportion to the current throgh it; instead of the pointer and scale of a direct-reading meter, the recorder deflects a pen or other marking device. Where greater senstivity and speed of response was required, the mirror galvanomter deflected a beam of light which was recorded photographically.
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