Patent ID: 6628396
Filing Date: 2003-09-30
Classification: G01N

Abstract:
A gas detector comprising:a radiation emitter; a first expansion receiver spaced from the radiation emitter by a sample distance, the first expansion receiver comprising: a chamber hermetically housing an expansion gas such that radiation from the radiation emitter is transmitted through a sample into the expansion gas, the expansion gas having a known composition which expands based upon intensity of radiation received; and a capacitive diaphragm sensor comprising: a movable capacitor plate area provided on a diaphragm which is impacted by the expansion gas; and a fixed capacitor plate, supported generally parallel the movable capacitor plate area and separated from the movable capacitor plate area by a dielectric gap which changes thickness when the diaphragm moves, the fixed capacitor plate and the movable capacitor plate area having a capacitance across the dielectric gap such that expansion of the expansion gas produces a corresponding change in capacitance; a control chamber sealed with a known control gas therein which receives radiation from the radiation emitter; and a second expansion receiver housing a control expansion gas such that radiation from the radiation emitter is transmitted through the control chamber into the control expansion gas the control expansion gas being separated from the expansion gas such that the gas detector can sense changes in the expansion gas relative to the control expansion gas.