Automotive Sensors and Signal Types

Automotive sensors fall into three signal categories. Voltage-generating sensors produce their own signal without a reference voltage—examples include the crankshaft position sensor (magnetic reluctance type producing an AC sine wave) and the oxygen sensor (generating 0.1-0.9V based on exhaust oxygen content). Variable-resistance sensors change resistance with a physical condition—the coolant temperature sensor decreases resistance as temperature rises (negative temperature coefficient), modifying a 5V reference signal. Digital sensors output a square wave or pulse train—the Hall-effect camshaft position sensor produces a clean on/off signal as a shutter wheel passes through the sensor.