Patent ID: 7418860

Claim:
A fluid level sensor for determining a fluid level within a container, comprising: a transducer for generating sonic or ultrasonic waves; instrumentation electronics; and a wave guide having a first end operatively coupled to the transducer and a second end for immersion into the fluid, said second end spaced a predetermined distance from the first end, wherein a gap is formed between the first end and the second end, wherein a sonic or ultrasonic wave generated by said transducer is injected into said wave guide, and wherein the instrumentation electronics use an impedance mismatch signal and a fluid conductance signal to determine the fluid level, wherein using the impedance mismatch includes monitoring an amplitude of a reflected wave created by the injected wave, and wherein monitoring the amplitude includes comparing the amplitude to a predetermined amplitude, said predetermined amplitude corresponding to a fluid level of interest, wherein when the amplitude is substantially the same as the predetermined amplitude, the instrumentation electronics conclude that the fluid level is at or above the level of interest, and when the amplitude is substantially different from the predetermined amplitude, the instrumentation electronics conclude that the fluid level is below the level of interest.