Temperature compensated pressure gauge

Claim 1

A temperature compensated pressure gauge for indicating the gas pressure being monitored relative to an acceptable operating zone defined by minimum and maximum allowable pressure limits over a predetermined temperature range, the gauge comprising: a pressure gauge housing including a visible dial face with a fixed marking indicating said minimum allowable pressure limit; a gas medium sealed in said housing, said gas medium having essentially the same pressure-to-temperature characteristic as that of a gas medium being monitored, said gas medium sealed in said housing being at said minimum allowable pressure, said housing being located in the same temperature environment as that of the gas medium being monitored and the contents of said housing being subject to essentially the same temperature; pressure sensing means including a first Bourdon coil mounted in said housing and disposed in said gas medium sealed therein, the interior of which coil being coupled to a port in said housing for communicating only with the gas medium being monitored, said first coil including a movable end portion operatively coupled to a first dial indicator member, a nontemperature related changing pressure differential of a gas medium in said first coil as compared to that of said gas medium sealed in said housing causing rotational movement of said movable end portion and of said first dial indicator member relative to said fixed marking on said dial face; and reference means including a second Bourdon coil mounted in said housing and disposed in said gas medium sealed therein, said second Bourdon coil having a gas medium with essentially the same pressure-to-temperature characteristic as that being monitored sealed therein and also having a movable end portion operatively coupled to a second dial indicator member, said second Bourdon coil having essentially the same pressure differetial-caused movement characteristic as that of said first Bourdon coil, the spatial relationship between said fixed marking on said dial face and said second dial indicator member for continuously defining sAid acceptable operating zone over said predetermined temperature range, said first dial indicator member indicating the pressure of a gas being monitored relative to said acceptable operating zone.