Quick reminder: to trigger the technicien or injection the calculator need to know on which cycle the motor is. To do that the simplest method consist on having a encoded wheel turning at the same speed than the motor and reading it’s state with a sensor. There seem to be two types of sensors : hall sensors and inductive sensors. The hall sensor is basically a transistor and can be used almost directly on a microcontroler. The inductive one is trickier but also cheaper : you need a special circuit or component to deal with it. Guess the one we find on almost every car ? Yeah the inductive one.
After running the car without sparkplugs and connected the sensor to a oscilloscope we can see this :
This is the direct output of the sensor. Here we can see that the signal between + and – 4V in a cycle that repeat at 11Hz. The motor is running at 660rpm !
