In recent years, transducer technology has been improved and more importantly echo processing software is more capable than ever before. It is fair to say that ultrasonic level sensors have been pushed to their physical limits. Even the most powerful ultrasonic transducers are affected by vapours, gas composition, excess dust, steam and condensation as well as filling noise and air movement. Obviously, ultrasonics do not work in a vacuum. Having said this, ultrasonics still provide a relatively low cost, non-contact level transmitter with ranges from less than one metre to 70 metres and above.
Ultrasonic transmitters are available with a variety of analogue and digital output options.
Non-contact ultrasonic level transmitters are used on liquids and solids with measuring ranges up to 70 metres. Longer ranges generally require larger, lower frequency transducers. They are able to measure liquids or solids through the wall of stainless steel or other metal vessels. This measurement technique, the differential adsorption of Gamma radiation from a radioactive isotope, such as Caesium Cs137 or Cobalt 60, is used to detect the level in the vessel. This radiation source is specially shielded so that the radiation is only directed towards the product through the vessel wall.