reflecting galvanometer with moving coil
Date: 1920-1940
Inventory Number: 1997-1-0317
Classification: Reflecting Galvanometer
Subject:
Maker: Leeds & Northrup Company (1903 - 1995)
Cultural Region:
Place of Origin:
Dimensions:
23 × 13.3 × 13.3 cm (9 1/16 × 5 1/4 × 5 1/4 in.)
Description:
A cylindrical black brass case on moulded circular bakelite base with three levelling screws and two binding posts on base. The cylinder has a long, narrow, rectangular glass window with brackets to attach a focusing lens. Behind the window is a small circular mirror suspended from a thin wire above and connected to a metal cylinder below, which lies at the center of a cavity between the poles of a magnet. Attached to the top of the magnet is the structure that supports the wire, which includes a zero adjustment screw and a screw that adjusts the clamp system for locking the coil when not in use. Both the zero adjustment and the coil clamp use the same removable knurled brass knob.
SignedLEEDS & NORTHRUP CO. / PHILADELPHIA PA
Inscribedon base, (serial number): 260625; on top of case, MADE IN U.S.A.
FunctionReflecting galvanometers are used to measure very small electrical currents and voltage differences. Instead of having a scale with a pointer, in these galvanometers a small mirror turns in the presence of electrical currents. The change of angle can be detected by shining a light at the mirror and observing the reflection on a large scale that is placed in front of the device. Alternatively, a scope is pointed at the mirror to see the change in the angle that the scope points to on a scale seen through the mirror. In those cases, the scales that are used are mirror-inverted.