Abstract: An ultrasonic sensor includes an ultrasonic transmitter, an ultrasonic receiver and a support structure. First and second elongated tubes are mechanically coupled to and extend from the support structure. A first elongated waveguide is operably coupled to the ultrasonic transmitter and extends through the support structure and a bore in the first tube. The first waveguide is acoustically isolated from the support structure and first tube except at a distal portion of the first waveguide. A second elongated waveguide is operably coupled to the ultrasonic receiver and extends through the support structure and a bore in the second tube. The second waveguide is acoustically isolated from the support structure and the second tube except at a distal portion of the second waveguide. A measurement gap is located between the distal portions of the first and second waveguides.

Abstract: An ultrasonic level instrument detects the presence of a fluid at a defined location and provides a self-diagnostic integrity check. An excitation circuit simultaneously induces vibrations at a first and second frequency in a transmitting piezoelectric crystal, and the vibrations are detected by a receiving crystal. A first and second filter circuit generate first and second filter outputs, respectively, by selectively passing the receiving crystal output at the first and second frequencies, respectively. The first filter output is indicative of the presence of fluid and the second filter output is indicative of the sensor integrity.

Abstract: A time gate ultrasonic sensor measures a physical property of a material, such as the presence of the material, within a defined space. The sensor includes at least one transducer connected to a support structure and positioned generally adjacent the defined space for transmitting and receiving ultrasonic signals across the defined space. The ultrasonic signals include a main waveform which travels across the defined space and a self-test waveform which travels along the support structure. The sensor monitors the received ultrasonic signals during a main time window to sense whether the main waveform is present in the received signals. The sensor senses the physical property of the material within the defined space as a function of whether the main waveform is present within the time window. The sensor performs a self-test each measurement cycle by determining whether the self-test waveform is present during a self-test time window which is different from the main time window.