Piezoelectric liq. level detector - uses two piezoelectric ceramic plates which form with liq. and transistor circuit an ultrasonic oscillator

摘要

The detector has a pair of piezoelectric elements mounted in and w.r.t. the liq. whose presence and level is to be detected. An active circuit forms with the piezoelectric elements and the liq. an ultrasonic oscillator. An alarm circuit is connected to the active circuit. The alarm circuit produces a warning signal as soon as the liq. reaches a predetermined min. level and is no longer between the pair of piezoelectric elements. The alarm circuit has a voltage converter designed to transform the ultrasonic signal delivered by the ultrasonic oscillator into a continuous voltage.