Patent ID: 8180582

Claim:
A system for detecting a presence of a liquid within a liquid receptacle, the system comprising: a sensor comprising a transmitting probe and a receiving probe positioned within the liquid receptacle, said transmitting probe comprising a first transducer and said receiving probe comprising a second transducer, said first transducer generating a first extensional wave through said transmitting probe that produces a compressional wave in a liquid contained within the liquid receptacle when the first extensional wave contacts an interface between said transmitting probe and a surface of the liquid, the compressional wave contacting said receiving probe and generating a second extensional wave within said receiving probe that is received by said second transducer; and a processor in electrical communication with said first and second transducers, said processor monitoring said first and second transducers to determine the presence and level of the liquid within the liquid receptacle based on a time between generation of the first extensional wave by said first transducer and reception of the second extensional wave by said second transducer, wherein said processor detects a transmit time for the first extensional wave to travel down a length of said transmitting probe, reflect, and return, wherein said processor detects an elapsed time from initiation of a transmit pulse in said first transducer to detection of a leading edge of the second extensional wave in said receiving probe, wherein said processor determines a difference between the elapsed time and the transmit time as time in the liquid, and wherein said processor determines the level of the liquid by multiplying a difference between the elapsed time and the time in the liquid plus a dry time in the dry portions of one or both of said transmitting and receiving probes by a length of one or both of said transmitting and receiving probes and dividing by the transmit time.