Ultrasonic sensor

Combined transmit/receive mode 

In the combined transmit/receive mode, the ultrasonic sensors first of all transmit a package of ultrasonic pulses in succession. Subsequently, the ultrasonic sensors receives the echo impulse that is reflected by an object in the detection range. This echo impulse is amplified in the ultrasonic sensor and forwarded as a digital signal to the junction box electronics (JBE). The JBE uses the operating time of the echo impulse to calculate the distance to the object.

Receive mode 

In the receive mode, an ultrasonic sensor picks up the echo impulses sent by neighboring ultrasonic sensors. The JBE can thus evaluate the signals from up to 3 ultrasonic sensors ("trilateration" = the neighboring sensors also "listen"). Evaluating the signals from multiple ultrasonic sensors in that way is used to calculate the smallest distance between the vehicle and the object.

Fig 1: Identifying Ultrasonic Sensor And Pin Plug Connection

Courtesy of BMW OF NORTH AMERICA, INC.

All the ultrasonic sensors have their own electronics. The front and rear ultrasonic sensors have a common voltage supply and a common ground connection on the control unit.