ETAS ES1337.2, User Manual

Page: 12 / 29

Hardware Features 12
2.1.1 Type “DF6”
A sensor of type “DF6” is a passive sensor consisting of a magnet wrapped in
a coil in the vicinity of an encoder gear wheel.
The coil and the magnet are mounted on the vehicle or the axle – the move-
ment of the teeth of the encoder wheel along one pole of the permanent
magnet generates an AC signal in the coil which is routed to the correspond-
ing ECU.
The resulting sensor signal approximates the form of a sinusoidal signal (see
Fig. 2-1).
Fig. 2-1 Signal of a Passive “DF6” Sensor
Every tooth generates a period of the sinusoidal oscillations – the signal ampli-
tude depends on the size of the gap between the individual teeth (the air gap)
and the speed. The greater the speed and the smaller the gap, the greater the
induced voltage.
A great disadvantage with this sensor type is the low signal amplitude with low
speeds.
Unfolded Gear
Wheel
Sensor Signal