Mirror galvanometer
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/* Kelvin's galvanometer */ He would patent the device in 1858.
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A mirror galvanometer is a mechanical meter that senses electric current, except that instead of moving a needle, it moves a mirror. The mirror reflects a beam of light, which projects onto a meter, and acts as a long, weightless, massless pointer. In 1826, Johann Christian Poggendorff developed the mirror galvanometer for detecting electric currents. The apparatus is also known as a spot galvanometer after the spot of light produced in some models.
Mirror galvanometers were used extensively in scientific instruments before reliable, stable electronic amplifiers were available. The most common uses were as recording equipment for seismometers and submarine cables used for telegraphy.
Kelvin's galvanometer
The mirror galvanometer was later improved by William Thomson, later to become Lord Kelvin. He would patent the device in 1858.
Thomson reacted to the need for an instrument that could indicate with sensibility all the variations of the current in a long cable. This instrument was far more sensitive than any which preceded it, enabling the detection of the slightest defect in the core of a cable during its manufacture and submersion. Moreover, it proved the best apparatus for receiving messages through a long cable.
The following is adapted a contemporary accountTemplate:Ref of Thomson's instrument: Template:Cquote
References
- Template:NoteMunro, J. Heroes of the Telegraph [1]