A low cost force sensing crystal resonator applied to weighing

摘要

A general-purpose, force-sensing crystal resonator has been developed that is low in cost. The very simple design uses the single-vibrating-beam approach and includes a dynamic isolator system at each end to maintain high Q. The beam is a rotated X-cut which exhibits a high turnover temperature (up to 38 degrees C) and performs very well in atmosphere as well as vacuum. Typical bias frequencies are from 20 to 26 kHz, depending on beam geometry, and they are capable of changing frequency typically +or-10% in response to 700-gm axial tension or compression forces, respectively. Weighing to an accuracy of better than one part in 20000 has already been demonstrated, and indications are that one part in 40000 or better is feasible.