ETAS ES1337.2, User Manual

Page: 13 / 29

Hardware Features 13
2.1.2 Type “DF10”
A sensor of type “DF10” is an active sensor in which the signal amplitude is
independent of the speed.
The magnetoresistance is made use of here which leads to the electrical resis-
tance of certain materials changing when they are brought into contact with a
magnetic field. Oscillations of the magnetic flux density correspondingly lead
to fluctuations in the resistance.
In addition to the actual sensor element, magnetoresistance sensors consists of
a permanent magnet and a two-wire connection for the power supply (battery
voltage) and the sensor signal.
This sensor is then positioned on the gear wheel so that there are changes in
the resistance due to changes in the flux density between the tooth and the
gap. The post-connected evaluation unit then returns defined currents of
7 mA (gap) or 14 mA (tooth).
Fig. 2-2 Output Signal of a “DF10” Sensor
The advantage of this principle is that the output signal is not speed-depen-
dent and thus speeds to value 0 can be acquired.
Sensor Signal
Unfolded Gear Wheel
7 mA
14 mA