I'm not sure whether this is HC-SR04 issue or this can be explained by physics. I was given a task by my professor to test out the precision of this sensor when measuring distances of objects of various materials and shapes. Everything seems fine, except for the fact that every cylindrical object I use (regardless of its material) seems to disappear off the radar precisely at the distances between 12 and 35 inches (30-90 cm) while all other objects can be detected at these distances. Has anyone else experienced this? I need to explain in final report what happened there, but I have no clue about it. I guess it has something to do with the way ultrasonic waves bounce off the curves. Does anyone here has any insight into this?
I guess it has something to do with the way ultrasonic waves bounce off the curves.
That is a pretty good guess.
Since sound waves behave the same as light waves in such respects, consult the optics section of an introductory college level physics textbook for more information.
Well, imagine if your a wave of sound hitting a round-ish object at X distance from a device that emits sound in a 15 degree cone at X distance, what would you do? Think about the properties of a near 40KHz signal and its behavior at X distance. Ask yourself why is the preferred side view of a submarine round, besides drag in relation to acoustical reflection?
Idahowalker:
Ask yourself why is the preferred side view of a submarine round, besides drag in relation to acoustical reflection?
Is it?
When it comes to radar reflection, boats and aircraft are made anything BUT round. This as for a round surface you always have some surface perpendicular to your signal; with flat surfaces only very occasionally.