Abstract: A capacitive level sensor for sensing level of a in a vessel includes a sensor coupled to the vessel having a shield and an inner sensing rod. An oscillator provides an RF signal to the shield and the sensing rod. Comparison circuitry couples to the sensing rod provides a wet/dry output in response to capacitance between the inner sensing rod and the vessel, the capacitance related to the level of the liquid in the vessel.

Abstract: An ultrasonic transducer for measuring a property of a material within a defined space has a function of a velocity at which ultrasonic signals travel through the defined space includes a controller. The controller is adapted for coupling to a plurality of ultrasonic transducers. The controller include a multiplexer for selecting one of the plurality of ultrasonic transducers, signal processing means for processing an output of the selected ultrasonic transducer and controller means for providing parameters to the signal processing means based upon the selected ultrasonic transducer. The controller couples to a two wire 4-20 mA communication loop. The controller periodically excites the ultrasonic transducer to obtain a measurement. The controller stores power received from the two wire communication loop and excites the transducer using stored power. The controller is capable of providing power which exceeds that available directly from the two wire communication loop for a brief period of time.

Abstract: An ultrasonic liquid level sensor includes an ultrasonic coupling element for use in self testing. The sensor includes a gap and a pair of transducers spaced apart by the gap. The sensor senses presence of liquid in the gap. The ultrasonic coupling element extends between the transducers and acoustically couples them together. The coupling element is used to test ultrasonic sensor integrity.