Rpm And Tdc Sensor; Principle Of Operation - Fiat 1998 Marea Service Manual

Marea-Marea
1998 range
Copyright Fiat Auto
Weekend®
16v

RPM AND TDC SENSOR

(Jaeger CVM02)
RPM and crankshaft angular position refer-
ence (TDC indicator) sensor (1) is secured to
the engine block facing phonic wheel (7) lo-
cated on the crankshaft pulley.

Principle of operation

This consists of a tubular case (1) containing
a permanent magnet (3) and an electrical coil
(2).The magnetic flux set up by magnet (3)
undergoes fluctuations due to changes in the
gap as the teeth pass in front of the phonic
wheel.
These magnetic flux changes set up an elec-
tromotive force in coil (2). An alternating
positive (teeth facing sensor) and negative
(gap facing sensor) voltage is set up at coil
terminals. The sensor output voltage peak
value depends on the gap beteween sensor
and phonic wheel teeth if all other factors are
equal.
Two of the sixty teeth on the phonic wheel are
removed to create a reference gap. Gear pitch
therefore corresponds to an angle of 6° (360°
divided by 60 teeth). The synchronism point is
recognised at the end of the first tooth follow-
ing the space left by the two missing teeth.
When this gap passes beneath the sensor, en-
gine piston pair 1 -4 is located at 114° before
TDC.
1. Sensor
2. Winding
3. Permanent magnet
4. Sensor connector
5. Output signal
6. Signal
7. Crankshaft
Engine
Fuel system
10.
corresonding
to the two missing
teeth
pulley
with phonic wheel
29