Fiber optic pressure detector

Claim 1

For use in apparatus for precisely monitoring ambient pressure within a confined space, said apparatus including a light source, a light detector, a source of fluid under pressure, control means for controlling the pressure of said fluid in accordance with light or darkness sensed by said detector and display means for displaying said pressure, a sensor unit comprising an envelope adapted to be placed within the confined space; a pneumatic line in communication with the envelope interior and adapted to be connected to said fluid source; a pair of light guides each having an internal end terminating within the envelope and, of whose external ends, one faces the light source and the other the light detector; said envelope having at least one wall movable in response to change of relative pressure between the envelope interior and the confined space; light beam modulating mechanism mounted within said envelope and relatively movable with respect to said internal ends responsive to movements of said movable wall; said internal ends and said mechanism being so disposed and arranged that in one position of said mechanism a beam of light will pass between said internal ends and, in another position of said mechanism, passage of said beam will be blocked; so that said control means acting through said pneumatic line will adjust the internal pressure in said envelope in accordance with the light condition sensed by said detector, thereby causing said mechanism repeatedly to shift between its two positions whereby the internal pressure in the envelope continuously spans a range of pressures sufficiently close to said ambient pressure to provide a measure thereof.