Truman Gravimeter

Gravimeters (gravity meters) are extremely precise instruments that measure the earth’s gravity at a specific location. Gravimeters are often used by prospectors to locate subterranean deposits of valuable natural resources (mainly petroleum) as well as by geodesists to study the shape of the earth and its gravitational field. Differences in topography, latitude, or elevation—as well as differences in subterranean density—all affect the force of gravity. Commonly, gravimeters are composed of a weight hanging on a zero-length spring inside a metal housing to negate the influence of temperature and wind. Gravity is then measured by how much the weight stretches the spring.
Orley Hosmer Truman built this gravimeter in his father's shop in San Diego, California, in 1932. He used a toggle joint rather than the lever used in the instrument that he had designed for the Humble Oil and Refining Co. (also in the collections). While using this gravimeter to locate oil bearing structures on the western coast of the Gulf of Mexico, Truman found that readings sometimes varied over time. Truman also met group of men testing the pendulum apparatus developed by the Gulf Research and Development Corp. and proposed a comparison between the two instruments; the result of this test convinced Gulf of the benefits of gravimeters. Truman donated this instrument to the Smithsonian in 1962.
Truman obtained two patents in 1935. The first (#1,988,527) described a "gravity meter." The second (#1,998,345) described a "gravity meter with compensator." Truman also held patent #1,963,252 for "optical torsion balance" and #2,316,915 for "apparatus for amplifying and measuring small displacements."
Ref: O. H. Truman, "Notes on the Truman Gravity Meter No. 2" (Sept. 1, 1962 and Feb. 20, 1955), and related photographs, in NMAH curatorial file.
O. H. Truman, "Variations of Gravity at One Place," Astrophysical Journal 89 (1939): 445-462.
overall: 48 in x 27 3/16 in x 40 3/16 in; 121.92 cm x 69.088 cm x 102.108 cm
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Credit Line
O. H. Truman
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Work and Industry: Agriculture and Natural Resources
Measuring & Mapping
Natural Resources
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National Museum of American History


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