A vacuum dilatometer based on the use of a linear variable differential transformer has been constructed. Expansion or contraction of the specimen moves a silica pusher‐rod which, in turn, changes the position of the core of the linear transformer. The output of the transformer is directly proportional to the displacement of this core. The output is amplified, rectified, and fed into the chart‐moving circuit of a function‐plotting potentiometer. The transformer is supplied by a 2000 cycle per second oscillator. By varying the input voltage to the transformer, magnification of the expansion curves can be increased or decreased as desired. The instrument has been used for about a year for the detection of solid phase transformations in alloys. Several curves are reproduced to illustrate the performance of the instrument.

Topics
Phase transitions, Resistors, Linear variable differential transformers, Thermal instruments
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L. L. Wyman, U.S. Atomic Energy Commission KAPL‐654 (November 15, 1951);
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Highly sensitive dilatometer
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R. K. McGeary, U.S. Atomic Energy Commission WAPD‐17 (June 28, 1950).
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Schaevitz Engineering Company, Camden, New Jersey.
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© 1955 American Institute of Physics.
1955
American Institute of Physics
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