Ultrasonic level sensor

The most common technologies available for continuous level measurement are ultrasonic, free space radar, guided wave radar, capacitance, gamma, and pressure. Lets learn about ultrasonic first.

Ultrasonic

An ultrasonic transducer generates a mechanical sound pulse that is directed through air to the process. When this pulse encounters the process surface, it bounces back to the transducer. The transmitter is basically a high-tech timer, measuring the time it takes the pulse to travel to the process and back. This time is directly proportional to the distance to the process surface.This time-based technology is referred to as time of flight (ToF). 

An ultrasonic level sensor sends a sound pulse that reflects from the surface of the liquid or solid in a vessel. 

Advantage

• Ultrasonic transmitters are used on a variety of simple applications for measuring liquid or solid level in a vessel. 
• The transducers are temperature compensated to give a high level of repeatable accuracy at distances of 2 to 230 feet.

Disadvantage

• Applications with heavy dust are not suitable and defuses the signal and causing a poor return.
• High temperatures or vapours can also alter the density of the air enough to affect the speed of the pulse transmission, causing errors in measurement.
• ultrasonic devices do not work in applications operating under a vacuum. 
• Foam on top of a liquid can also disrupt an ultrasonic signal.