Force measurement device with piezoelectric crystal - has zero point temp. drift error compensation using periodic counter force from controlled solenoid

摘要

The force measurement device has a mechanical electrical transducer (12) consisting of a piezoelectric crystal whose resonant frequency varies with the applied force. The force is applied to the crystal via a transfer device. The difference between loaded and unloaded crystal frequencies is measured. Null point drift errors arising partic. from temp. dependent frequency shift during long measurement periods are compensated for. An electrical-mechanical transducer (24) is coupled to force transfer device and connected to a control arrangement whereby a force opposing the measured force is periodically applied to the transfer device to remove the force on the crystal.