Fiat 1996 Brava Service Manual page 441

Bravo-Brava © i
'98 range
lev
Engine
Fuel system
10.
RPM AND TDC SENSOR
(Jaeger CVM02)
The sensor (1) for rpm and reference of the
crankshaft angle (identification of TDC) is
secured to the engine block and is opposite
the phonic wheel (7) located on the
crankshaft pulley.
Principle of operation
The sensor consists of a tubular case (1)
containing a permanent magnet (3) and
electrical winding (2). The magnetic flow
created by the magnet (3) causes oscillations
following the change of gap, because of the
passage of the teeth of the phonic wheel.
These oscillations induce an electromotive
force in the winding (2) at the^ends oiwhich
there is a voltage which is alternately positive
(tooth opposite the sensor) and negative
(gap opposite the sensor). Provided all other
factors are equal, the peak output voltage
from the sensor depends on the distance be­
tween sensor and tooth (gap).
The phonic wheel has sixty teeth, two of
which are removed to create a reference; the
pitch of the wheel thus corresponds to an an­
gle of 6° (360° divided by 60 teeth). The point
of synchronization is recognized at the end of
the first tooth following the two missing teeth;
when this space passes under the sensor, the
engine is with the piston pair 1 -4 at 114° be­
fore TDC.
1. Sensor
2. Winding
3. Permanent magnet
4. Sensor connector
5. Output signal
6. Signal corresponding
to the two missing
teeth
7. Crankshaft pulley
with phonic wheel
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