High-Sensitivity Photoelastic Pressure Sensor

Laurence N Wesson

doi:10.1117/12.937522

28 April 1987 High-Sensitivity Photoelastic Pressure Sensor

Laurence N Wesson

Proceedings Volume 0718, Fiber Optic and Laser Sensors IV; (1987) https://doi.org/10.1117/12.937522
Event: Cambridge Symposium-Fiber/LASE '86, 1986, Cambridge, MA, United States

Abstract

By selecting the proper geometry for the reactive element of a photoelastic sensor a considerable improvement in sensitivity over conventional intensity-modulated sensors can be achieved. Other recent photoelastic sensors have consisted of an essentially rectangular prismatic bar of transpqrnt material which is stressed uniformly by a strut connected to a force-summing diaphragml,L. Our alternative is to fabricate the diaphragm itself of a transparent material and use it for both the reactive and force-summing functions. In the basic form reported here the diaphragm consists of a thin glass plate mounted and sealed with zero residual stress on a circular support and subjected to varying differential pressure. Polarized light is directed into one edge of the plate along a diameter and received through an analyzer at the opposite edge. Analysis of the,resulting modulation in received optical power with crossed polarizers shows it to be a sin 4 function of applied differential pressure. The photoelastic phase delay is a linear function of pressure and parameters related to the geometry and material of the plate. For thin plates with maximum sen-sitivity the phase delay is proportional to the cube of the support radius and inversely proportional to the square of the plate thickness. An essentially linear response at zero pressure can be achieved with a quarter wave plate (thick sensor plates) or prestressing (thin sensor plates). Tests on experimental models have shown performance consistent with theory, with a response of 3.68 x 10-4 rad/pbar obtained with a 0.023 cm thick glass plate sealed on a 2.32 cm radius support. Extensive theoretical formulae and experimental data are presented.

Citation Download Citation

Laurence N Wesson "High-Sensitivity Photoelastic Pressure Sensor", Proc. SPIE 0718, Fiber Optic and Laser Sensors IV, (28 April 1987); https://doi.org/10.1117/12.937522

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