System and method for ultrasonic measurement of material level

A system for monitoring level of material that comprises:

• transducer means for transmitting ultrasonic signals toward and receiving echo signals from a surface of the material,
• switch means for selectively connecting and disconnecting said transducer means to and from a source of electrical power for energizing and de-energizing said transducer means,
• microprocessor-based control means having an output coupled to said switch means for controlling operation thereof, said output providing a pulsed periodic signal at variable frequency, duty cycle and total time duration to operate said switch means at an ultrasonic frequency that corresponds to said periodic signal frequency, at a duty cycle that corresponds to said periodic signal duty cycle and/or a time duration that corresponds to said periodic signal time duration,
• receiver circuit means coupled to said transducer means for receiving signals from said transducer means corresponding to echo signals from the material surface and providing said signals to said microprocessor-based control means, said receiver circuit means having an input for controlling gain of said receiver circuit means, and means coupled to said input and responsive to said control means for increasing gain of said receiver circuit means with time between each burst transmission at said transducer means, and
• means coupled to said control means for determining system range between minimum and maximum material levels, said gain-increasing means being responsive to said control means for increasing gain of said receiver circuit means in a predetermined number of discrete steps over a total time duration that corresponds to said minimum and maximum material levels.

A method of determining level of material as a function of round-trip transit time of ultrasonic signals between a transducer and a surface of the material comprising the steps of:

• (a) transmitting a series of ultrasonic signals toward the material surface,
• (b) monitoring for echo signals from the material surface between each ultrasonic signal transmitted in said step (a),
• (c) comparing amplitude of the echo signals to a plurality of differing amplitude thresholds, and
• (d) distinguishing between a true echo signal from the material surface and false echo signals as a function of echo signals whose amplitudes exceed a higher threshold than other of said echo signals.

A system for monitoring level of material that comprises:

• transducer means for transmitting ultrasonic signals toward and receiving echo signals from a surface of the material,
• microprocessor-based control means including means coupled to said transducer means for controlling operation thereof,
• receiver circuit means coupled to said transducer means for receiving signals from said transducer means corresponding to echo signals from the material surface and providing said signals to said microprocessor-based control means, said receiver circuit means having an input for controlling gain of said receiver circuit means, and means coupled to said input and responsive to said control means for increasing gain of said receiver circuit means with time between each burst transmission at said transducer means, and
• means coupled to said control means for determining system range between minimum and maximum material levels, said gain-increasing means being responsive to said control circuit means for increasing gain of said receiver circuit means in a predetermined number of discrete steps over a total time duration that corresponds to said minimum and maximum material levels.

A system for monitoring level of material that comprises:

• transducer means for transmitting a series of ultrasonic signals toward a surface of the material and receiving echo signals in response to each said ultrasonic signal,
• means coupled to said transducer means for comparing amplitude of said echo signals to a plurality of amplitude thresholds,
• means for distinguishing a true echo signal from the material surface from false echo signals as a function of echo signals whose amplitude exceed said thresholds, and
• means for determining the level of said material surface as a function of round-trip transit time of said time signal from and to said transducer means.