Direct coupled pressure sensing device

Abstract

Pressure sensing devices which have a vibrating crystal or other load sensitive component responsive to external pressures and a reference component of the same character for outputting a signal which accurately reflects the magnitude of the external pressure and is obtained by ascertaining the difference between the sensing and reference components output signals. Preloading is employed in installing the sensing component, eliminating the need for bonding and/or mechanical connections and thereby reducing the cost of manufacturing and the potential error in output from the device. A component with a displaceable element such as a bellows or diaphragm is employed to preload the sensing component and to detect external pressure force, and provision is made for limiting the travel of the displaceable element so that the sensing of an external pressure exceeding design limits will not result in the sensing component being loaded to a level which might damage it or cause hysteresis. The reference component is mounted to a compliant support arrangement which preloads that component and subjects it to the same mechanical stiffness as the sensing component. That compensates for thermal coefficient of expansion mismatches, changing temperatures, dimensional instabilities, assembly stresses, and forces attributable to acceleration of the pressure sensing device.