Car parking sensors
Many car parking sensors send out ultrasound pulses that reflect off objects such as walls, kerbs and nearby cars.
A receiver detects the reflected ultrasound, and the time taken for the waves to leave a sensor and return to the detector is measured.
Using this time, the distance from the car to the object is calculated electronically, using distance = speed of ultrasound in air multiplied by the time taken.
This is an echo method so it is important that only the outward time from the sensor to the object is used in the calculation.
If the car is too close to an object, warning bleeps are sounded, and the dashboard displays warning lights.
Ultrasound is used rather than sound waves so that pedestrians and other road users don鈥檛 hear the pulses of waves sent out from the parking sensors.
Problems:
- The sensors can be affected by snow, rain and wind which can reduce accuracy or cause the system to fail.
- Individual sensors are mounted on the car鈥檚 bumper 鈥 dirt and mud can cause the system to fail.