A galvanometer uses movements of a coil within a magnetic field or a magnetic needle to measure or detect a small electric current. The galvanometer was the first instrument that scientists used to pick up and quantify electrical currents, and these devices were the first to locate electrical activity in the brain and heart.
The first scientist to observe that a wire with current could deflect a magnetic compass needle was Hans Oersted, who described the phenomenon in 1820. The most common modern applications for a galvanometer deal with control and positioning systems. Mirror galvanometer systems function as beam steering or beam positioning elements within systems for laser scanning. Closed loop mirror galvanometers have applications in laser engraving, laser sintering, stereolithography and laser bean welding, as well as laser television and displays and retinal scanning.
Open loop mirror galvanometers primarily function within barcode scanners that use lasers, as well as in some printers, space systems, military applications and imaging programs. Uses that require a significant level of vacuum make their non-lubricated bearings quite useful. The positioning servos in hard drives and compact disk players also use a galvanometer mechanism, and all of these use the moving coil type of galvanometer to keep the overall mass of the system low.