LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> BMW >> 2001 >> M3 2D Convertible >> Repair and Diagnosis >> Restraints >> Restraints Control Systems >> Passive Safety Systems - Technical Training (E46) >> Passive Safety Systems >> Roll Over Protection System >> Components of the System: >> Clinometer
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Components of the System:: Clinometer

The clinometer inside the sensor consists of three level floats to detect body tilting, transverse and longitudinal acceleration for roll bar deployment. two floats are positioned on opposing angles of 52 degrees to the horizontal axis of the vehicle. The third float is positioned at an angle of 72 degrees to the longitudinal axis. LED transmitters and phototransistor receivers are positioned to read the air bubble float as it moves in the glass tube.

Fig 1: Clinometer Operation Diagram
G03395890Courtesy of BMW OF NORTH AMERICA, INC.

If the vehicle starts to roll over sideways or end-to-end, beyond the critical angles, the air bubble will move and interrupt the LED signal. The electronics of the sensor will then trigger the solenoids and the roll bars will deploy.