Galvanometer
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A galvanometer is an electromechanical measuring instrument for electric current. Early galvanometers were uncalibrated, but improved versions, called ammeters, were calibrated and could measure the f
An early D'Arsonval galvanometer showing magnet and rotating coil
Close-up view (rear) of a permanent magnet type moving coil meter
Closed-loop galvanometer-driven laser scanning mirror
A galvanometer mechanism (center part), used in an automatic exposure unit of an 8 mm film camera, together with a photoresistor (seen in the hole on top of the leftpart).
Mirror galvanometer
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A mirror galvanometer is an ammeter that indicates it has sensed an electric current by deflecting a light beam with a mirror. The beam of light projected on a scale acts as a long massless pointer. I
Galvanometer
…Later instruments of the "astatic" type used opposing magnets to become independent of the Earth's field and would operate in any orientation. An early mirror galvanometer was invented in 1826 by Johann Christian Poggendorff. An astatic galvanometer was invented by Hermann von Helmholtz in 1849; a more sensitive version…
Thomson mirror galvanometer of tripod type, from around 1900
Galvanometer by H.W. Sullivan, London. Late 19th or early 20th century. This galvanometer was used at the transatlantic cable station, Halifax, NS, Canada
A moving coil galvanometer with its glass cover separated and mirror absent