What is the principle of an automotive speed sensor?
2 Answers
Automotive speed sensor principle is to detect the vehicle's driving speed and input the detection results to the vehicle instrument system for displaying the speed. As the information source of the automotive electronic control system, the automotive speed sensor is a key component of the automotive electronic control system and one of the core research areas in automotive electronic technology. The automotive speed sensor detects the speed of electronically controlled vehicles, and the control computer uses this input signal to control engine idle speed, torque converter lock-up in automatic transmissions, automatic transmission shifting, engine cooling fan operation, cruise control, and other functions. Automotive speed sensors can be classified into magnetic speed sensors, Hall-effect speed sensors, and photoelectric speed sensors.
I have been working in automotive R&D, and the working principle of speed sensors is primarily based on magnetic induction to measure speed. Specifically, it is usually installed near the wheel or transmission, with a small magnet rotating on a moving part. When the wheel turns, the magnetic field of the magnet changes, which is captured by a sensing chip or coil. The chip, like a Hall element, outputs electrical signal variations. These pulse signals are sent to the vehicle's computer (ECU), which quickly calculates the current speed based on the pulse frequency and displays it on the dashboard. It also affects the anti-lock braking system and cruise control, so a malfunction can cause erratic speedometer readings or safety risks. During maintenance, pay attention to loose connections and waterproofing, as moisture can easily lead to corrosion. Electronic sensors are much more reliable than old mechanical ones, but repairs can be time-consuming if issues arise.
