reflecting galvanometer with moving coil
Date: circa 1927
Inventory Number: 0538
Classification: Reflecting Galvanometer
Subject:
Maker: Leeds & Northrup Company (1903 - 1995)
User: Department of Physics, Harvard University (founded 1884)
Cultural Region:
Place of Origin:
City of Use:
Dimensions:
22.5 × 13.5 × 15.5 cm (8 7/8 × 5 5/16 × 6 1/8 in.)
Accessories: none
Description:
CAT 2500, Type R. Cylindrical black brass case on moulded bakelite base with three levelling screws and two binding posts. The cylinder has a long, narrow, rectangular glass window. Behind the window is a small circular mirror suspended from a thin wire above and connected to a metal cylinder (a coil) below, which lies at the center of a cavity between the poles of a large magnet. Most of the magnet's body is hidden by the black cylindrical case. It is of an inverted U shape. Attached to the top of the magnet is the structure that supports the wire, which includes a zero adjustment screw (at the center), as well as a clamp system for locking the coil when not in use (off-center). Both the zero adjustment and the coil clamp use a large removable brass knob.
Signedon base between the binding posts, raised letters: LEEDS & NORTHRUP CO. / PHILADELPHIA PA
Inscribedon base, underside: (serial number): 72725
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.
Provenancefrom Jefferson Laboratory (Harvard University), 04/27/1970.