Piezoelectric cell for liquid level measurement includes two cells producing reference and measurement ultrasound pulses

摘要

The system has a second cell enabling calibration prior to the liquid level measurement. The liquid level measuring system includes a detection set (Si) including two concentric piezoelectric cells (10,12) associated with controls for transmitting ultrasonic waves. The waves from one cell (12) are reflected from a surface (16) at a known distance (D) above the cells, and the waves from the other cell (10) are reflected from the surface of the liquid (14). Processing is carried out on the propagation times of the waves to determine the liquid level. The operating process includes an initialising phase during which the piezoelectric cells are controlled such that the ratio between the excitation rate of the reference cell (12) and the level-measuring cell (10) is higher than the ratio between those same rates during the subsequent stabilised measuring phase.