Ultrasonic level switch with sanitary transducer uses pulsed signal technology for superior performance in difficult process conditions, and to provide excellent immunity from sources of electrical noise interference. It is suitable for a wide variety of critical level applications. The high frequency ultrasonic pulses are transmitted across a transducer gap in the presence of a liquid medium, but are attenuated when the gap is dry. It is ideal for low level alarm, seal pot level and leak detection applications.