Abstract: Pressure sensing diaphragms comprise a cylindrical or spherical crystalline member in which an internal cylindrical or spherical chamber is provided. In the internally loaded embodiments, a fluid is introduced into the chamber and the pressure exerted by the fluid causes generally tensile stress in the region of the diaphragm generally about the chamber. In the externally loaded embodiments, the diaphragm is immersed within the fluid and the pressure exerted by the fluid causes generally compressive stress in the region of the diaphragm generally about the chamber. For each of the embodiments, the stresses arising cause certain mechanical and electrical properties of the crystalline material to change. The change in these properties is detected by observing the frequency behavior of one or more oscillators whose frequencies of operation are controlled by respective surface acoustic wave devices provided in the regions of elastic deformation.

Abstract: A stress compensated thickness-shear resonator is of an orientation (yxwl) .phi./.theta. selected from loci of stress compensated orientations provided for both the fast and slow thickness-shear modes of vibration. A stress compensated orientation is used in an oscillator for stable frequency-stress behavior. A stress compensated orientation having large-valued temperature coefficients of frequency is used in a temperature sensor for precision measurements. A stress and temperature compensated orientation is used in a pressure sensor such that the temperature compensated thickness-shear mode is used for pressure measurement while the stress compensated thickness-shear mode is used to compensate for effects of temperature.