What are the types of vehicle speed sensors?
2 Answers
Vehicle speed sensors are categorized into magnetic speed sensors, Hall-effect speed sensors, and optical speed sensors. The vehicle speed sensor is a device used to detect the speed of electronically controlled vehicles. The control computer utilizes this input signal to regulate engine idle speed, torque converter lock-up in automatic transmissions, automatic transmission shifting, activation/deactivation of engine cooling fans, cruise control functions, and other operations. Typically installed in the drive axle housing or transmission case, the sensor's signal wires are encased in shielded conduits to mitigate electromagnetic and radio frequency interference from high-voltage ignition systems and electronic equipment. This ensures uninterrupted electronic communication and prevents degraded driving performance.
In my years of driving experience, there are quite a few types of vehicle speed sensors, with the common ones being wheel speed sensors and output shaft sensors. Wheel speed sensors are installed on the wheels, used for the ABS system to measure the rotation speed of each wheel. They are generally magnetoelectric or Hall-effect types. For example, Hall sensors are triggered by magnetic wheels, offering fast response and fewer errors. Output shaft sensors are located near the transmission and control shift smoothness, often using similar designs. The older magnetoelectric types rely on changes in the magnetic field of a coil but are prone to interference from iron debris. Photoelectric types use light sensing for detection but are sensitive to dust and fog, making them rare in vehicles. Additionally, GPS speed sensors in newer cars assist in displaying vehicle speed, but the core still relies on mechanical sensors. Sensor failures can lead to unstable braking or jerky gear shifts, so it's best to regularly clean wheel speed sensors to prevent the ABS light from coming on.
