The two-way or reflective ultrasonic barrier operates in a similar way to a photoelectric barrier. However, in contrast to the photoelectric barrier, no special triple reflector or similar device is needed. Any reflector, e.g. a metal flag, is adequate. In this case the ultrasonic sensor is set up in window mode in such a way that the fixed reflector lies within the window. The reflective ultrasonic barrier supplies a signal as soon as an object completely obscures the reflector. It does not matter whether the target absorbs all the sound or even 'deflects' it. Therefore, this operating mode is used for foams and other materials difficult to detect and for scanning objects with irregular surfaces.
The two-way or reflective ultrasonic barrier
