Specifications

Engine Management and Data Acquisition SystemsPage 30
Pole Diameter
It is important to remember when designing a trigger wheel with a mag sensor, that the width of
the tooth in degrees should be no less than 1 times the width of the pole piece in degrees and no
more than 2 times this number of degrees. Some mag sensors have a stainless steel shield on them
making it difficult to see the true pole diameter. Rub the sensor in some steel shavings to give you
an idea of the pole piece size.
Mag Sensor Rising Edge Polarity
Missing Tooth / Mag Sensor Falling Edge Polarity
When viewing the waveform on a labscope, the direction of travel of the voltage line as it
crosses the 0v line determines the sensors active edge. is edge will not deviate in time with
respect to RPM. e opposite edge will. is corresponds to the point at which the trigger
tooth passes the center of the sensor.
To know for sure if you sensor produces a rising or a falling edge you need a Digital
Volt/Ohm Meter or DVOM. Disconnect the ECU from the Harness. Plug the red
lead of the meter into the signal terminal of the ECU Header and the black lead to
the 0v terminal. Place a steel object (like a screwdriver) against the sensor. Set the
DVOM to read DC volts. Quickly remove the metal from the sensor and watch the
direction the voltage goes either positive or negative. If the voltage goes negative, the
sensor is wired as a falling edge sensor. If the voltage goes positive, the sensor is wired
as a rising edge signal.
Rising or Falling edge?