There is a tendency, at least in the industrial media, to put Ultrasonic and Radar level measurement technology in the same hat. Even though many people use the terms interchangeably, the two technologies are quite different.
So, at the risk of sounding a bit nit-picky, we feel that defining the differences is important, as it affects how sensors are selected and applied.
Ultrasonic level sensors operate by emitting a burst of sound waves in very rapid succession. These sound waves hit the intended target, bounce back to the sensor, and travel at known speed (the speed of sound). We can calculate time of flight and come up with a distance.
Radar, by contrast, works not with sound waves, but with electromagnetic waves. This is the key difference.
There is a different set of variables that affects how well a radar sensor operates. Unlike ultrasonic sensors, radar is much less affected by temperature, improving consistency and accuracy.