What is the Principle of Ultrasonic Sensors?
2 Answers
Ultrasonic sensors operate by converting ultrasonic signals into energy signals. Ultrasonic waves possess characteristics such as high frequency, short wavelength, minimal diffraction, and particularly strong directionality, enabling them to propagate directionally like rays. Ultrasonic waves exhibit significant penetration capabilities in liquids and solids, especially in opaque solids. When encountering impurities or interfaces, ultrasonic waves produce notable reflections, forming echo signals. Additionally, they generate the Doppler effect when interacting with moving objects. Ultrasonic sensors utilize sound wave media to perform non-contact, wear-free detection on objects. These sensors can detect transparent or colored objects, metallic or non-metallic materials, as well as solids, liquids, and powdered substances. Their detection performance remains unaffected by any environmental conditions, including smoky or rainy environments.
I've disassembled quite a few reverse parking sensors. The ultrasonic sensor actually works similarly to how bats navigate. Inside, there's a transmitter that emits high-frequency sound waves inaudible to human ears, typically around 40 kHz. When these sound waves hit an obstacle, they bounce back. The receiver clicks upon detecting the echo, and the chip inside the sensor starts timing. By calculating the round-trip time of the sound wave and multiplying it by the speed of sound in air (approximately 340 meters per second), then dividing by two, you get the distance from the rear bumper to the obstacle. For example, a 0.1-second echo translates to about 17 meters. Interestingly, in cold winter air where sound travels slower, the measurements can drift slightly. I've encountered several false radar alerts during repairs due to this reason. If the sensor surface gets covered in mud, the readings become even less accurate – so remember to wipe those little circular dots when washing your car.
