Technician Handbook ! 673 Electronic & Computer Controlled Systems Pulse Pattern Input Another type of ECU input is a pulse pattern. When voltage rises momentarily, then falls, the transient voltage reading is called a pulse . When a component creates multiple pulses, the result is a pulse pattern (or pulse train). An active wheel speed sensor is a component that generates a pulse pattern. A magnetic ring mounted on the wheel hub has alternating north-south fields that are detected by the sensor pickup. As the wheel rotates, the alternating magnetic fields are converted into a series of voltage pulses. The frequency of the pulses increases with the wheel rotation speed.
When the pulse pattern is provided as ECU input, the ECU’s circuits are able to measure the pulse frequency and calculate wheel RPM and vehicle speed. 12 Technical Training