The galvanometer is a current measuring device. Gustav H. Wiedemann's version of the galvanometer was developed in 1874. The coils on either side of the suspended needle could be moved back and forth to change the sensitivity, and a series of coils, ranging from 2000 Ohms down to about 6 Ohms, was provided. Damping was provided by surrounding the magnet with a copper ring or sphere. He employed a mirror attached to the lower part of the torsion fiber to act as an optical lever to increase the sensitivity of the instrument. This version was sold by Queen of Philadelphia. A somewhat similar galvanometer is listed in the 1887 Queen catalogue of electrical testing apparatus at $156.00.
Property of the W&L Physics & Engineering Department
“Wiedemann's Galvanometer,” Digital Exhibits at Washington and Lee University Library, accessed January 23, 2018, http://omeka.wlu.edu/items/show/204.