In the past ultrasonic sensors for measuring corrosive media levels or in applications involving machinery and equipment being cleaned with corrosive liquids could often not be used. This was very much down to the corrosive effect on the ultrasonic transducers of these liquids and their emitted gases. The special zws sensor design involves the entire sensor housing - including the ultrasonic transducer - being provided with a special parylene protective coating. The result is that the whole of the sensor is hermetically protected.