Subaru 2002 Impreza Service Manual page 312

ANTI-LOCK BRAKE SYSTEM (ABS)
ABS
D: ABS SENSORS
Each of the ABS sensors detects the speed of the corresponding wheel. The sensor consists of
a permanent magnet, coil and tone wheel. The magnetic flux produced by the permanent magnet
changes as each tooth of the tone wheel (which rotates together with the wheel) passes in front
of the magnet's pole piece. The changing magnetic flux induces voltages at a frequency corre-
sponding to the wheel speed.
(A)
(B)
(A) Front
(B) Rear
(4)
+ v
I
/
(3)
\
I
i
-V
i
(1 )
Sensor body
(4)
Full speed
(2)
Pole piece (5) Low speed
(3) Tone wheel (6) Permanent magnet
NF0200
ABS-6