| 摘要 |
A disk-like piezoelectric crystal element having an axis of maximum strain sensitivity has a pair of electrodes sputter deposited on opposite faces. A pair of annular resilient spacers are disposed one over each electrode on the piezoelectric element and a cover is disposed over each spacer to form an air gap respectively between the cover and the electrode and forms a transducer subassembly. A torsion member to be subjected to an applied torque has an area prepared, preferably recessed and the subassembly disposed in the recess with the axis of maximum strain sensitivity oriented at about 45 DEG to the torque axis. The subassembly has electrical leads attached and is potted in the recess with strain transmitting potting compound such as epoxy. The electrical leads are coupled to an external oscillator circuit via a rotary variable capacitive coupling. The circuit determines the changes in the heterodyned frequency of the oscillator and the resonant frequency of the strained piezoelectric crystal element as an indicator of torsional strain in the torsion element. The variable capacitance provides an indication of rotary angular position. <IMAGE> |
