Load sensor using a piezoelectric S.A.W. device

摘要

A load sensor includes a fixed rigid portion, a movable rigid portion spaced from the fixed rigid portion and adapted to receive an applied load, and a shear-deformable member provided between the two rigid portions. The shear-deformable portion is provided with a transmission and a reception transducer constituting an elastic surface-wave oscillator. When a load is applied to the movable rigid portion, weight is sensed based on a deviation in the oscillation frequency of the elastic surface-wave oscillator. The fixed and movable rigid portions, as well as upper and lower beams interconnecting these portions, constitute a load-sensitive element. The latter has a side face which is closed off by a pliable membrane for sealing the shear-deformable element disposed within the load-sensitivie element. Alternatively, a corrugated bellows is connected across the fixed and movable rigid portions to seal the shear-deformable member within the bellows.