An analysts of the longitudinal mode quartz tactile sensor based on the Mason equivalent circuit

A tactile sensor was developed by use of a longitudinal mode quartz crystal resonator. Its behavior in contact with viscoelastic mediums was analyzed based on the Mason equivalent circuit. The problem of acoustic impedance of an oscillating sphere in semi-infinite viscoelastic media has already been analyzed. On the assumption that the top shape of the quartz resonator is spherical, the Mason equivalent circuit was applied to this acoustic impedance. Finally, theoretical equations were obtained for frequency and impedance changes. The theoretical equation for frequency change includes both density and shear modulus of silicone rubbers as parameters. Shifts in frequency were correlated with measurements from both viscoelastic and rubber testers. The frequency changes were found to correspond to the hardness or softness of the rubbers. It has been confirmed that the theoretical equation for frequency change is in good agreement with experimental results