What does effectual angle ultrasonic sensors mean?


I want to use an obstacle detection sensor on my machine which is about 18" wide. I am looking for ultrasonic sensor that can give me a horizontal angle range of 45 degrees. When I look up sonar sensors it doesn’t mention the angular range. There is a spec for effectual angle which is 15 degrees. What does this mean? At what distance from the sensor does the 15 degrees range apply?

(My machine is 18" wide and I want to be able to detect a distance of 65" in width at 20" and more in front of the machine. I am trying to determine how many sensors I will need to place on the 18" surface which is at a height of 12" above the ground)


Ultrasonic sensors will detect objects that are not “directly ahead” (at zero degrees) but offset at some angle as as well. The detection efficiency drops as the angle increases, but many manufacturers will settle on some definition for detection (e.g. 50% of the time) and give you the range of angles over which detection occurs.

I suspect that the 15 degree number you are quoting is for either side of zero, so the sensor will detect objects over a range of about 30 degrees (+/- 15 from zero). This will only be true within a certain distance from the sensor, of course.

The detection efficiency depends a great deal on the object itself, i.e. the geometry and the surface acoustic reflection characteristics, so you may need to determine the characteristics of your particular setup by experimentation. Just mount the sensor in such a way that you can rotate it, and check the distance readings to see if the object is still being detected, as you rotate away from zero degrees.