Automotive Electronics

Distance Sensors - Acoustic

Basic Description

The most common automotive applications for acoustic distance sensors are for back-up warning systems and parking assistance systems. Acoustic distance sensors generally cost less than comparable RADAR sensors and they are more accurate for detecting objects a short distance away.

acoustic waves reflecting off an object

Acoustic distance sensors work by transmitting an acoustic signal (sound) and "listening" for the reflected signal. The delay associated with reception of the reflected signal can be correlated to the distance of the reflecting object. Acoustic sensors generate a signal by moving a diaphragm quickly back and forth displacing the air around the diaphragm, creating an acoustic wave.

acoustic sensor diaphragm deflection

Acoustic distance sensors usually operate at ultrasonic frequencies (40 - 250 kHz). Ultrasonic sensors are very good at detecting objects, that are relatively large compared to ultrasonic wavelengths (~1cm). Ultrasonic signals propagate in air, so acoustic sensors may not be reliable in situations where the air is moving at a high speed unless the air speed can be measured and compensated for. Acoustic sensors also have difficulty making a reliable measurement in acoustically noisy environments.

Balluff, BeStar, Bosch, Di-Soric, Longsun, MaxBotix, Microsonic, Migatron, Mitsubishi Electric, Murata, Pepperl+Fuchs, Rockwell Automation, Sandtron, Senix, SensComp, Sick, Wenglor
For More Information
[1] Ultrasonic Sensor, Wikipedia.
[2] Ultrasonic Parking Sensor Kit, Apogee Kits.
[3] Choosing an Ultrasonic Sensor for Proximity or Distance Measurement Part1, Donald P. Massa, Sensors, Feb. 1,1999.
[4] Choosing an Ultrasonic Sensor for Proximity or Distance Measurement Part2, Donald P. Massa, Sensors, Feb. 1,1999.
[5] Ultrasonic Sensors with Engineer Jim Lindblom, YouTube, June 8, 2010.
[6] A Sensitive DIY Ultrasonic Range Sensor, Kerry D. Wong blog, Jan. 22, 2011.
[7] Ultrasound Sensors, Sensorwiki.
[8] Vauxhall Parking Sensors - Xvision, YouTube, May 29, 2012.