ABSTRACT
The development of a dual-mode thickness-shear quartz pressure sensor to meet the demanding performance requirements of oil-field applications is discussed. The objective was to develop a sensor with an operating pressure range of 0-103.42 MPa (0.15 000 lb/in(2)), a temperature range of -10 to +175 degrees C, a pressure calibration accuracy of 6894.8 Pa (1 lb/in(2)), and resolution of 68.95 Pa (0.01 lb/in(2)) with 1-s counter gate time. Doubly rotated cuts with piezoelectric coupling to both the C-modes of vibration were investigated. A theoretical study and general design considerations in the development of such sensors are described. Experimental results were obtained for two sensor designs: one uses a cylindrical design with the SBTC-cut, and the other, called SPA, is a special resonator design vibrating around 5 MHz without any activity dips. Pressure sensitivity of approximately 145 Hz/MPa (1 Hz/lb/in(2)) at 175 degrees C is obtained. Laboratory evaluation of the static and dynamic performances is discussed for the prototypes based on the SPA design.
