There is an infinite number of applications for liquid level sensors, and each one has its own specific needs. If your application involves the tank level measurement of certain difficult liquids, then you may require a non-contact liquid level sensor.
Difficult liquids in this context can include acids and other corrosive materials that will degrade or damage traditional float switches, as well as highly viscous materials like oils, liquid waste, and slurries. For liquid media such as these, an ideal option is an ultrasonic liquid level sensor.
What Are Ultrasonic Liquid Level Sensors?
Ultrasonic liquid level sensors are high-tech, non-contact devices that are mounted to the top of the vessel. The device’s transducer sends ultrasonic sound pulses similar to sonar or radar, usually between 20 to 200 kHz. The sonic pulses travel 
downward in a conical beam through the air, reflect off the surface of the liquid, and then return as an echo to the transducer.
By measuring the interval between the emission and return of each pulse, the sensor is able to calculate the distance to the liquid’s surface and by extension it’s level relative to the vessel.
Ultrasonic gauges can be used for point level or continuous liquid level sensing, making it a versatile choice across applications.
There are, however, some situations for which an ultrasonic liquid level sensor is not ideal. Foam, chemical vapor, steam, and excessive turbulence can all impair the sensor’s accuracy, due to the fact that that absorb or otherwise interfere with the transfer of sound waves through the atmosphere. Ultrasonic sensors are also ill-suited for vessels with solid obstructions, as they also interfere with the pulses of sound.
If you need a non-contact level sensor for difficult fluids and think an ultrasonic unit might be just what you need, contact SMD Fluid Controls. They have a full line of stainless steel and plastic ultrasonic sensors, including the FL50 and FL-LL, as well as a team of engineers ready to bring your custom solutions to life.