reflecting galvanometer
Date: circa 1940
Inventory Number: 0537
Classification: Reflecting Galvanometer
Subject:
Maker: Leeds & Northrup Company (1903 - 1995)
Maker: Department of Physics, Harvard University (founded 1884)
Cultural Region:
Place of Origin:
City of Use:
Dimensions:
22.5 × 13 × 13 cm (8 7/8 × 5 1/8 × 5 1/8 in.)
Description:
CAT 2500, TYPE R. Brass cylindrical case on moulded circular bakelite base with three levelling screws and two binding posts. The cylinder has a long, narrow, rectangular glass window, slightly tipped back and 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 (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 the same removable knurled brass knob.
Signedon base between the binding posts in raised letters: LEEDS & NORTHRUP CO. / PHILADELPHIA PA
Inscribedon base, front: (serial number): 235287; moulded flap swings out from underneath the base with the meter's specifications (see Card); on case, top: 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.
Curatorial RemarksLittle blue triangle indicates this instrument was used for teaching the Physics 3 course at Harvard.
Provenancefrom Jefferson Laboratory (Harvard University), 04/27/1970.