When it comes to ultrasonic sensor targets, bigger, flat, smooth, and reflective is better. The surface, the angle, size, and distance can all affect how well an ultrasonic sensor can detect and measure an object.
The ideal target surface is hard, flat, and smooth. This type of surface will reflect a greater amount of signal than a soft or uneven surface. A target with poor sound wave reflection characteristics will reduce the operating distance of the sensor and decrease its accuracy. Because of this, ultrasonic sensors are typically great solutions for liquid level measurement in tanks. Liquids are self-leveling, and in most tanks are relatively still.
Agitation tanks are an exception where an ultrasonic sensor may not be the best solution, depending on the intensity of the turbulence. Other liquid level applications in tanks that may not work well for ultrasonic sensors are where heavy foam or thick vapor layers may be present. These can either absorb or disrupt the ultrasonic wave, as discussed in our post about ultrasonic sensors and air columns.
Distance can also affect the accuracy of an ultrasonic sensor. The closer an object is to the transducer face, the stronger the returning echo. The farther an object, the better the reflective characteristics need to be to return a sufficient echo. Most sensors work well in a range of a few inches up to about 50 ft.
A large object with a greater surface will be easier to detect at greater distances. Small, soft, or non-reflective surfaces become very difficult to detect at longer distances.
Finally, one last obstacle is the angle. Typically, anything more than 5° off perpendicular will not be detected. While there seems to be more than a few things that can disrupt an ultrasonic, most are easy to avoid. For more on how an ultrasonic works, check out our explanation of ultrasonic sensor technology.
Before considering an ultrasonic sensor first look at the object being measured or detected. For more information on using ultrasonic technology for your applications contact us at 888-525-7300, or via email.
Image by Roger McLassus