portable galvanometer with moving coil
Date: circa 1920
Inventory Number: 0553
Classification: Galvanometer
Subject:
Maker: Weston Electrical Instrument Corporation (founded 1888)
User: Department of Physics, Harvard University (founded 1884)
User: Jefferson Physical Laboratory, Harvard University (founded 1884)
Cultural Region:
Place of Origin:
City of Use:
Dimensions:
6 × 16.7 × 10.5 cm (2 3/8 × 6 9/16 × 4 1/8 in.)
Description:
Galvanometer with moving coil in rectangular molded bakelite case with window for scale above. The paper scale has 1-mm divisions from 30-0-30 mm and is marked with specifications. Two push buttons on the front of the case labeled "1" and "2" are located directly below two binding posts. Seal on cover screw still unbroken. Base of case has four rubber pads.
Signedon metal plaque on front of case: WESTON ELECTRICAL INSTRUMENT CORP. / NEWARK N.J. U.S.A. / Model 440 No 5985
on paper scale: WESTON GALVANOMETER
on paper scale: WESTON GALVANOMETER
Inscribedon metal plaque on front of case (serial number): 5985
marked on bottom "018"
on on scale: RES = 3.6 OHMS 1 DIV = 2.2 x 10^-6 AMP
marked on bottom "018"
on on scale: RES = 3.6 OHMS 1 DIV = 2.2 x 10^-6 AMP
FunctionThis portable pointer galvanometer is a sensitive instrument that was used for measuring current in the classroom. It consists of a coil with an attached needle suspended between the poles of a magnet. When an electric current is introduced into the coil, it induces a magnetic field, causing the coil to rotate in proportion to the current. This galvanometer was designed to be used in circuits where two currents are balanced against each other using a bridge or potentiometer until the scale reads zero. There are two push buttons on either side of the scale opening labeled "1" and "2." Button No 1 closes the galvanometer circuit through a high resistance to prevent damage if the circuits to be tested are considerably out of balance. No 2 closes galvanometer circuit directly to obtain maximum sensitivity.
Curatorial RemarksDescription handwritten on card: "Supersensitive indicator to replace the delicate suspended coil. Reflectory type. surface type. A rectangular moulded bakelite case with window for scale above, two push buttons "1" & "2", 2 binding posts on end, 4 rubber pads. (con't below) From Jefferson lab first floor 1-19-72. Marked on bottom "018". The paper scale marked 30mm either side of 0 centercenteripointer 2 mirror below for paralax. Ratings given on scale: Weston Bulletin 502 1923. Res= 3.6 ohms 1 Div = 2.2 X 10-6 amp. External Res. for critical (2.2 micro amp) damping = 7.9 ohms Model 440 No 5985. There are two push buttons on either side of the scate opening. No 1 closes the galvanometer circuit through a high resistance to prevent damage if the circuits to be tested are considerably out of balance. No 2 closes galvanometer circuit directly to obtain maximum sensitivity. Seal on cover screw still unbroken."
ProvenanceFrom Department of Physics, Jefferson Laboratory, Harvard University, 1/19/1972.