Ultrasonic sensor

An improved ultrasonic system for determining a distance to an ultrasonic reflecting surface comprising:

• ultrasonic transducer means for transmitting ultrasonic signals and controlled to cease transmission of signals after a selected time period but which transducer means continues to vibrate, ring down, and send ultrasonic signals having a decreasing magnitude after the transducer means has been controlled to cease transmission, and including means for receiving ultrasonic signals, the time interval between the transmission of the transmitted ultrasonic signals and the receipt of a respective reflected return signal representing the distance from the transducer means to the ultrasonic reflecting surface;
• reference means coupled to the transducer means for generating a reference signal;
• means coupled to the transducer means for comparing the received signals to the reference signal, and providing a comparator output when a received signal is greater than the reference signal;
• means for controlling the reference signal at a level that is substantially representative of the magnitude of signals which emanate from the transducer means after the transducer means has been controlled to cease transmission, such that signals due to ring down are substantially eliminated as a source of comparator outputs but reflected return signals provide comparator outputs even before ring down ceases;
• and
• means for measuring the time between the transmission of a transmitted signal and a corresponding comparator output and for providing an indication of the distance from the transducer means to the reflecting surface.

An ultrasonic distance measuring system for detecting distance from a transducer to an ultrasonic wave reflecting surface by measuring the time between commencement of transmitting an ultrasonic signal in response to a control signal and the time of receipt of a reflected return signal received by the system, which return signal has a magnitude, the measured time being representative of the distance to the surface, wherein the transducer continues to vibrate and cause reducing magnitude ultrasonic signals for a time after the control signal has ceased, comprising:

• means for comparing the return signal to a reference signal and for providing a comparator output
• means for providing the reference signal at a controlled magnitude which is greater than the magnitude of the signals from the transducer sensed when the control signal commences transmitting said ultrasonic signal, and which reduces the reference signal as a function of time after the control signal has ceased, to maintain the reference signal magnitude above but substantially corresponding to the reducing magnitude ultrasonic signals caused by the vibration of the transducer after the control signal has ceased;
• and
• means for measuring the time between the commencement of transmission of the ultrasonic signal and the corresponding comparator output and for providing an indication of distance from the transducer to the ultrasonic reflecting surface as a function of such time.

A method of measuring the level of a material in a space comprising:

• transmitting an ultrasonic signal toward the material level, the ultrasonic signal having a selected controlled duration and the transmitting ceasing after a preselected period of time, the ultrasonic transducer having the characteristic of continuing to vibrate to form a continued ultrasonic signal of decreasing magnitude for a period of time after such transmitting ceases;
• providing a transducer output signals from the transducer as a function of signals received thereby subsequent to transmission including ultrasonic signals reflected from the material in the space;
• comparing the transducer output signals with respect to a reference signal to determine when an output signal is greater in magnitude than the magnitude of the reference signal and then providing a comparator output;
• maintaining the reference signal at a sufficient magnitude which is greater in magnitude than the transmitted signal during transmission of the ultrasonic signal;
• thereafter reducing the magnitude of the reference signal to a level as a function of time, so that the reference signal maintains a magntiude higher than the continued ultrasonic transducer output signal magnitude caused by vibration of the transducer after transmission has ceased as the continued ultrasonic signal decreases in magnitude;
• and
• measuring the time from initiation of a transmitted signal to receipt of a comparator output representing receipt of a corresponding reflected signal and determining the level of material from such time.