Piezoelectric weighing device

摘要

A piezoelectric device is used to determine the absolute weight of an unknown sample by comparison to a control sample whose weight is known. A piezoelectric driver is resiliently attached to a base that is isolated from vibrations. A piezoelectric receiver and a reed are resiliently attached to the piezoelectric driver so that (1) the reed is moved in response to motion of the piezoelectric driver, and (2) the piezoelectric receiver gives an electric signal out proportional to motion of the system. The entire system is set to operate on the leading edge of the resonant frequency for the system. By applying an oscillating sine wave voltage, such as 140 hertz, to the piezoelectric driver, and by applying a known mass to the tip of the reed, a first output is obtained from the piezoelectric receiver which represents the calibrated weight. Next by exchanging an unknown sample for the known mass, a second output is obtained that represents the second weight. By a ratio of the second output/first output (or a signal equivalent to the weights being measured), the absolute weight of the unknown sample is determined.