About a month ago, we gave you Part 1 of our series on the top 10 mistakes made in selecting, installing, and using ultrasonic sensors. The first part covered mistakes ten through six.
Today, we'll wrap it up with the remaining five:
The transducer face of the sensor must be perpendicular to the target in order to receive the maximum sound wave energy reflecting back. This is even more important as the sensing range increase.
Not all materials and objects are good targets for an ultrasonic sensor, nor are all environments compatible with transmitting or receiving sound wave signals. Highly vaporous liquids create a constantly shifting atmospheric density, which affects the speed of sound, and can greatly reduce the accuracy of the readings. Soft or otherwise sound absorbent materials such as powders, foamy surfaces, and others can drastically reduce sensing ranges. Areas with extreme dust can attenuate the signal. There are many other sensors that can do the job of an ultrasonic when the application is not a fit.
The sound wave signals travel in the shape of a cone, similar to the beam of a flashlight (getting wider as distance increases). Mounting too close to potential unwanted targets, such as pipes, fill streams or even tank walls, if they aren’t smooth, can cause false or unstable readings. Stilling pipes are often a good solution when mounting in restricted spaces.
An ultrasonic transducer cannot generate a sound wave signal and pickup a signal returning from a target at the same time. Because of this, there is an inherent dead-zone beginning from the face of the sensor and extending outward. This dead-zone is known as the blanking distance, and extends anywhere from a few inches to more than a foot, depending on the frequency of the sensor. The sensor needs to be mounted in a location where the target will not come closer than the published minimum sensing range of the sensor.
Ultrasonic sensors are often adjusted incorrectly (too fast, too sensitive, etc). For example, some targets move quickly, others very slowly. Settings that work well for one will not be ideal for the other. It is human nature to think that more is better, which often leads to higher gain settings and faster target sampling than required, and overzealous signal filtering settings. It is good practice to take a minimalistic approach to sensor settings, not setting values to levels that are higher than required by the application.
Keep these tips in mind as you select, install, and use ultrasonic sensors. While they can be tuned to match your application like a glove, doing it wrong can have the opposite affect.
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