Ultrasonic distance sensor and a method for protecting an ultrasonic transducer in an ultrasonic distance sensor

Abstract

An ultrasonic level sensor () for monitoring the level of a liquid in a vessel comprises a main housing () having a lower part () and an upper part (). An ultrasonic transducer () having an output face (), through which ultrasonic signals are transmitted and received is housed in a sub-housing () located in an engagement recess () in the lower part (). A communicating aperture () accommodates ultrasonic signals transmitted by the ultrasonic transducer () to and from the liquid surface, the level of which is to be monitored. The sub-housing () comprises a cylindrical side wall () extending upwardly from a protective element () for protecting the ultrasonic transducer (). The protective element () comprises a circular disc of resilient material impermeable to corrosive gases and vapours in the vessel, the liquid level of which is being monitored, and comprises a central working portion () of diameter similar to that of the output face (), and an outer peripheral portion () extending around the central working portion () of thickness greater than the thickness of the central working portion (). The central working portion () is of constant thickness of approximately 0.35 mm and in its relaxed state is convex when viewed from the ultrasonic transducer (), and is deformable into a planar configuration to abut and vibrate in unison with the output face () of the ultrasonic transducer () to minimise attenuation of the ultrasonic signals.