There is a common misconception that ultrasonic level sensors and radar type sensors are the same, but they are not. In fact, both the sensors have their own unique strengths and weaknesses that distinguish them from each other. In today’s blog, we’ll explore the differences between the two technologies.
What is an ultrasonic sensor?
Ultrasonic liquid level indicators are level sensors that emit a series of ultrasonic pulses in very short bursts. The ultrasonic pulses move with a predetermined velocity towards the target, where they travel back and forth from the target.
The time taken for the burst of sound to reach the sensor after getting transmitted is used to calculate the distance from the sensor to the measured substance or the measured level of the substance. The measured distance can also be used to calculate other parameters such as weight, volume, etc.
Ultrasonic level sensors are designed to detect the level of a target substance. To do this, an open air column must be present between the target and the sensor. Physical obstructions, large amounts of foam, large amounts of heavy vapors, dense dust, or light powders can obstruct or absorb the signal or act as an impenetrable surface, resulting in false readings from an ultrasonic level sensor.
Unlike ultrasonic level sensors that emit sound waves, radar level sensors emit electromagnetic waves. The electromagnetic waves emitted by radar level sensors constitute the main difference between an ultrasonic level sensor and a radar level sensor.
Just as the waves emitted by ultrasonic level sensors bounce off the surface of an object, the electromagnetic waves are emitted because of a radar level sensor travels at a known velocity. While ultrasonic sound waves travel at a fixed velocity, radar’s electromagnetic waves interact differently with different materials as they reflect from the surface of the object.
Unlike other level sensors, radar level sensors are sensitive to a variety of variables. Radar level emitters are less sensitive to temperature compared to ultrasonic level emitters. This makes them more consistent and accurate.
Radar level emitters also work well for specialized applications. For example, they can operate in absence of air or at higher pressures if the house can tolerate it. Radiometer emitters are also not that sensitive to foam, vapor, and dust, which can disturb ultrasonic level signals and cause false readings. This makes radar level emitters more suitable for these applications.
Dielectric constant is an important parameter to consider when designing radar level sensors. A low value means that the material won’t reflect an EM wave, which is why radar usually passes right through. Di-electric materials are non-conducting and have a lower level of moisture. Examples include granules, dry powders, etc.
Radar can identify a large number of di-electric materials, but because the returning is very low, precise alignment of the signal to the material is very important. This is where techniques like guided wave radar or special antenna come in. Though it’s not impossible to measure di-electric materials, it’s very difficult.