Temperature-compensated induction extensometer

Rev Sci Instrum. 1978 Dec;49(12):1684. doi: 10.1063/1.1135346.

Abstract

A linear displacement transducer, or extensometer, has been designed and constructed to measure displacements over a range of 0-150 mm. The transducer works by electromagnetic induction and consists of a bifilar coil coaxial with two conducting cylinders, one inside and the other outside the coil. The induction extensometer has been designed to eliminate errors caused by temperature changes from 0 degrees to 1000 degrees C. Experimental measurements show an error of 1 mm over the 150-mm displacement range for a temperature change of 500 degrees C, and the error should not be larger over the full 1000 degrees C temperature range. The displacement range can be varied from 2.5 to 250 mm by scaling the entire experiment up or down, and the temperature compensation can be made for any temperature range that is compatible with the constructional materials.