Ultrasonic Sensors and Air Columns


Vapor layers can disrupt the air column between an ultrasonic sensor and its targetAir is vital to life, but did you know it is also vital to the performance of your ultrasonic sensor? While ultrasonic sensors are very versatile, being used in applications from object profiling to level measurement, they require an unobstructed column of air through which to sense.

Air density is the core variable that can cause an ultrasonic sensor to have a slight drift in accuracy, or a completely false reading. The type of material you are measuring can affect this column of air. For example, some liquids can produce significant amounts of foam or heavy vapors; other material can produce large amounts of dust and particles in the air. All of these variables can affect the ability of the ultrasonic to see the true target and give accurate results.

To solve some of these issues, you can mount your ultrasonic sensor in a stilling pipe. This will allow the liquid to rise in the pipe without creating foam. The pipe must have smooth walls, and must be free of build-up. These irregularities in the pipe could affect the sound waves from the ultrasonic sensor. Check out our recent article titled “The Art of the Stilling Well” for tips on proper stilling pipe use.

If you are measuring grains or other materials that produce dust, an ultrasonic may not be an affective technology to use. Grains create dust in the air, which makes it difficult for an ultrasonic sensor to get through to the target. They also tend to pile into a cone shape, causing the sound waves to reflect in different directions, and making a good reading very difficult to obtain. Look for more information on how the shape of targets and the angle of refraction can affect ultrasonics in a future post.

It’s important to note that ultrasonic sensors can perform quite well when any of these adverse conditions exist within reason. Only when dust, foam, or vapors are heavy, will the sensor begin to experience difficulty.

Contact us directly for more information on using ultrasonic technology for your application.

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