Design and fabrication of compact load sensor using AT-Cut quartz crystal resonators

The load sensor with AT-cut quartz crystal resonator has the characteristic that the resonant frequency changes by the external force, which achieves high sensitivity, high-speed response, and wide measurement range by a simple structure. Also it has the superior feature in the temperature and frequency stability. On the other hand, the quartz crystal resonator had been hardly applied to a force measurement because of low degree of mechanical characteristic, that is, it is weak to the impact, bend, and tension. The objective of this study is to construct the sensor mechanism that safely maintain the quartz crystal resonator for the external force with flat structure. We designed and analyzed a novel retention mechanism of the quartz crystal resonator for the flat structure. The size of the retention mechanism is 6.0 mmx5.0 mmx4.4 mm. The sensitivity of this sensor is 360 Hz/N. Output fluctuation of the sensor was less than 0.05 ppm when the static pressure of 1.5 MPa was applied. The proposed load sensor is small, sensitive and stable for static force measurement.