Contact type liquid level sensing system

Claim 1

A contacting type liquid level sensing system comprising: transducer means to come into contact with the liquid, said transducer means having a first portion, a piezoelectric element mounted within said first portion, and a second portion spaced from said first portion and defining a gap between said first and second portions, means for transmitting successive bursts each having a number of pulses, of electrical energy to said piezoelectric element to cause it to vibrate to produce corresponding bursts of pulse of sonic energy which are transmitted across the gap to said transducer means in the presence of a liquid, said transmitted sonic energy being attenuated in the absence of a liquid, means for receiving the successive bursts of pulses of sonic energy incident upon said second portion for converting the individual pulses of said received bursts of pulses of sonic energy into first electrical signals, and processing circuit means including pulse counter means coupled to said receiving means and responsive to the presence of a predetermined number of said first signals converted from a predetermined number of said successive bursts of pulses for indicating the presence of liquid in said gap and to the absence of said predetermined number of first pulses for indicating the absence of said liquid.