Development of a force sensor for minute load measurement

A force sensor for minute load measurement that consists of a load-sensing part, with a piezoresistive silicon diaphragm sensor, and a load-conducting part has been developed. The actuator, as a load conductor, combined with a gimbal leaf spring, transmits part of the applied force to the diaphragm surface with no friction. Its maximum displacement is restricted by a spacer to prevent the thin diaphragm from breaking. The mechanical parts were assembled by means of a diffusion welding process. The sensor structure, the force-sensing element, the leaf spring, and typical transfer characteristics are described. The sensor achieved 19.4 mV/gf force sensitivity in a 70-gf load range, and saturation characteristic for over 70 gf load. The output voltage was 1360 mV and diaphragm center displacement was 9.2 μm for a 70-gf load