string oscillograph
Date: ca. 1928-1932
Inventory Number: RS0359
Classification: Oscillograph
Subject:
Maker: General Radio Company (1915-present)
Cultural Region:
Place of Origin:
Dimensions:
14 x 20 x 19 cm (5 1/2 x 7 7/8 x 7 1/2 in.)
Description:
A pair of U-shaped permanent magnets, amidst the poles of which is an electrical mechanism including a thin metal wire. A horizontal cylindrical cavity traverses the system and contains several optical elements to illuminate the string and project its shadow out towards one side. The opposite side has a larger cylinder for the lamp and more lenses.
Mounted on a black insulating base. Also on the base is a potentiometer to regulate the amount of electricity passing through the system.
Mounted on a black insulating base. Also on the base is a potentiometer to regulate the amount of electricity passing through the system.
Signedetched and white filled on base: STRING / OSCILLOGRAPH / TYPE 338 SERIAL NO. 289 / GENERAL RADIO CO. / CAMBRIDGE, MASS.
FunctionString oscillographs were devices used to visualize rapidly varying electric currents or voltages. They worked by converting the signal into vibrations on a thin string. Early string oscillographs would have a mirror or other elements mounted on the wire to reflect light off.
Later examples, such as this one, were meant to be much more sensitive by using much thinner wires. Instead of having some element mounted on the wire, these devices visualized the electric signal by projecting the shadow of the wire as it moves in response to the signal.
In order to convert this left-right movement into a more visual, graph-like image, this oscillograph could be used in conjunction with a set of rotating mirrors, which displaced the image in a direction perpendicular to the wire movement. Later on, General Radio also offered a camera system to instead record the up-and-down movement on rolling photographic film.
The string oscillograph became less popular in the early 1930s with the implementation of the sweep circuit, which made the cathode ray tube oscillograph a much easier way to visualize electric signals than was the use of rotating mirrors or cameras.
Later examples, such as this one, were meant to be much more sensitive by using much thinner wires. Instead of having some element mounted on the wire, these devices visualized the electric signal by projecting the shadow of the wire as it moves in response to the signal.
In order to convert this left-right movement into a more visual, graph-like image, this oscillograph could be used in conjunction with a set of rotating mirrors, which displaced the image in a direction perpendicular to the wire movement. Later on, General Radio also offered a camera system to instead record the up-and-down movement on rolling photographic film.
The string oscillograph became less popular in the early 1930s with the implementation of the sweep circuit, which made the cathode ray tube oscillograph a much easier way to visualize electric signals than was the use of rotating mirrors or cameras.
Curatorial RemarksThe rotating mirror mechanism for this type of oscillograph can be seen in object RS0613.
Primary SourcesThis particular string oscillograph, including the rotating mirror arrangement, is described in:
Charles L. Reutz, Modern Radio Reception (New York, 1928), pp. 71-74. Available on Google Books here.
The photographic recording system for this oscillograph is described in:
Horatio W. Lamson, "A Continuous-Film Camera for the Oscillograph". The General Radio Experimenter, Vol. V. No. 11 (April 1931). Available online here.
Charles L. Reutz, Modern Radio Reception (New York, 1928), pp. 71-74. Available on Google Books here.
The photographic recording system for this oscillograph is described in:
Horatio W. Lamson, "A Continuous-Film Camera for the Oscillograph". The General Radio Experimenter, Vol. V. No. 11 (April 1931). Available online here.
