Proximity sensors for ADAS

By Pam Oakes, MACS Instructional Content Designer – Published on 7/22/2025

From those annoying backup “beeps” from the 1990s to today. Automotive proximity sensors for the advanced driver assist system (ADAS) world take on many forms nowadays: electromagnetic, infrared (IR), and the more well-known ultrasonic. Capacitive sensors are also used (for example) with some keyless entry systems.

Electromagnetic: These low frequency electrical fields identify when the waveform has been disturbed by signaling an object within vehicle range to the driver via instrument panel and/or a form of hepatics to signal the potential crash. Manufacturers utilize the technology to recognize key detection and unlock the car or light truck.

Infrared (IR): Utilizing infrared light to detect objects, it relies upon the return beam reflected onto the sensor. Therefore, a quick-timed return indicates that the object is close, versus a longer-timed response. This format is especially useful in detecting heat-emitting objects like a human or animal within the beam’s path. And some manufacturers use IR to detect the human hand – with key fob present – to lock or unlock a car or light truck. This technology is also incorporated into the interior of the vehicle. For example, passenger movement for supplemental air restraint deployment or child/pet identification and preventing child/pet heat induced deaths.

Ultrasonic: The most recognizable to vehicle owners and technicians everywhere are those little circles on front and rear bumper skins – the ultrasonic sensor. Used for parking assistance to low-speed obstacle detection, the sensors bounce high-frequency sound waves (well above the human hearing range) and, again, measure the time the return wave is received back (echo) to the sensor on the car or light truck. While very affordable, these sensors are only accurate between 12 to 20 feet (depending upon year/make/model) and are susceptible to inclement weather conditions.

Capacitive: Capacitive sensing technology works by measuring changes in an electrical field. A capacitive sensor essentially acts as one plate of a capacitor. When a conductive object, such as a human hand, comes into close proximity or touches the sensor, it changes the electrical field and thus the capacitance of the sensor. The sensor’s electronics detect this change, interpreting it as a “touch” or “presence.” When a user with the car’s smart key in their possession touches the inside of the door handle (where they would normally grasp it to open the door), the capacitive sensor detects the change in capacitance. If the vehicle’s system verifies the presence of the smart key, it will then unlock the door.

Although widely used, these components have limited skills and incorporate their detection data to other ADAS sensor applications.

Figure 1: Door handle proximity sensors, generally, can be electromagnetic, IR or capacitive. Follow the featured module’s interdependence upon other ADAS systems. Credit: Ford

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Edited 7/23/25 ss