Measurement Principle
Back warning system (BWS) is a complementary device for reversing. BWS detects objects behind vehicle and provides the driver with buzzer alarm finding objects in a certain area, using ultrasonic wave propagation speed and time.
The propagation speed formula of ultrasonic wave in air is following:
v=331.5 + 0.6t (m/s)
v=ultrasonic wave propagation speed
t=ambient temperature
The basic principle of distance measurement using ultrasonic wave is:
NOTE:
- 14cm (dia.) plastic rod is used for the test target.
- The test result may differ by a different target object.
- Detection range may be reduced by dirt accumulated on sensor, and extremely hot or cold weather.
- The following object may not be detected.
- Sharp object or thin object like rope.
- Cotton sponge, snow or other materials absorbing sonic wave.
- Smaller objects than 14cm (dia.), 1m length.