electron oscillograph and Bedell sweep circuit
Date: c. 1935
Inventory Number: RS0088
Classification: Oscillograph
Subject:
Maker: General Radio Company (1915-present)
Inventor: Frederick Bedell (1868 - 1958)
User: Department of Physics, Bowdoin College (founded after 1794)
Cultural Region:
Place of Origin:
City of Use:
Dimensions:
46 x 49 x 21 cm (18 1/8 x 19 5/16 x 8 1/4 in.)
Description:
Large rectangular wooden case with rounded black painted handle on top and 4 discoidal feet on bottom.
On one of its narrow sides, the case has a round, white cathode-ray-tube screen.
On one of the broad sides is the control panel, which includes 2 large (focus and sweep frequency) and 3 smaller (brilliancy, multiple sweep frequency, power switch) dials, 3 connectors (2 control and 1 unmarked ground), 2 red indicator lights, 2-pronged plug, and an inset circle with 5 connectors.
On one of its narrow sides, the case has a round, white cathode-ray-tube screen.
On one of the broad sides is the control panel, which includes 2 large (focus and sweep frequency) and 3 smaller (brilliancy, multiple sweep frequency, power switch) dials, 3 connectors (2 control and 1 unmarked ground), 2 red indicator lights, 2-pronged plug, and an inset circle with 5 connectors.
Signedetched and white filled on front panel: ELECTRON OSCILLOGRAPH / AND / BEDELL SWEEP CIRCUIT / TYPE 687-B SERIAL NO. 286 / GENERAL RADIO CO. / CAMBRIDGE, MASS. / U.S. PATENT 1,707,594
Inscribedstamped in white on top: 12
FunctionThe electron oscillograph is an electronic device that is used to observe rapidly varying signal voltages as a graph on a screen.
Oscilloscopes and oscillographs are most often used to detect the exact wave shape of an electric signal.
For more information on the function of oscilloscopes, see the wikipedia page here.
General Radio was one of the initial developers of the oscillograph, and starting in 1934, it produced the 687A type, which was the first to integrate the Sweep Circuit invented by Professor Frederick Bedell of Cornell University. This is the electronic system that allows the oscillograph to stretch the (up-and-down) voltage fluctuations on the screen as a graph. Until then, watching the wave pattern required the use of additional visual mechanisms such as a string oscillograph and rotating mirrors or cameras.
The instrument was not perceived by General Radio as having much commercial potential, and the rights to its development were sold to RCA and DuMont, which used them to develop Television and the Oscilloscope respectively.
Oscilloscopes and oscillographs are most often used to detect the exact wave shape of an electric signal.
For more information on the function of oscilloscopes, see the wikipedia page here.
General Radio was one of the initial developers of the oscillograph, and starting in 1934, it produced the 687A type, which was the first to integrate the Sweep Circuit invented by Professor Frederick Bedell of Cornell University. This is the electronic system that allows the oscillograph to stretch the (up-and-down) voltage fluctuations on the screen as a graph. Until then, watching the wave pattern required the use of additional visual mechanisms such as a string oscillograph and rotating mirrors or cameras.
The instrument was not perceived by General Radio as having much commercial potential, and the rights to its development were sold to RCA and DuMont, which used them to develop Television and the Oscilloscope respectively.
ProvenanceFrom the Physics Dept. Bowdoin College, Brunswick, Maine. Collected on May 14, 1991. Courtesy of Prof. Elroy Lacasce.
