Optical Pressure Transducer

Hank Lin† and Chih-Ming Ho‡

†Research Asistant, Department of Aerospace Engineering, University of Southern California, Los Angeles, CA 90089-1191.

‡Professor, Mechanical, Aerospace and Nuclear Engineering Department, University of California, Los Angeles, Los Angeles, CA 90024-1597.

Review of Scientific Instruments, Vol. 64, No. 7, July 1993, pp. 1999-2002.

ABSTRACT

This paper presents the characteristics of an optical pressure transducer using fiber optics. The transducer consists of a cylindrical housing with a reflective mylar diaphragm attached at one end and fiber-optic bundle at the other. The fiber-optic bundle used is the bifurcated type, in which two bundles of randomly distributed fibers are joined at one end to form a Y-shaped geometry. The common end is attached to the end of the transducer housing, opposite to the diaphragm. At the branched ends, one bundle is connected to a dc light source, while the other bundle carries the light reflected from the diaphragm to a photodetector. By keeping the input light source at constant intensity, the amount of reflected light depends on the distortion of diaphragm due to pressure differential across the diaphragm surface. This pressure transducer can measure both the static pressure level and the fluctuating pressure. A simple "homemade" diaphragm was used in this experiment, and a sensitivity of approximately 10 mv per mm Hg was obtained over a range of 20 mm Hg. The dynamic response was linear to about 2 kHz. Both the sensitivity and the frequency response can be much increased by improving the diaphragm performance.

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