Magnetic speed sensors

Hall-effect wheel speed sensors and speed sensors for automatic transmission systems are where magnetic speed sensors see a dominant part of their usage. Today, wheel speed and transmission measurements are integral in order for intelligent functions to operate smoothly in vehicles.

Magnetic wheel speed sensors

It used to be that only antilock braking systems (ABS) needed to know if a wheel was blocked, and only electronic stability control (ESC) used the speed of all four wheels to course correct vehicles veering away from their intended path. However, as car technologies have advanced, wheel speed has become an essential measurement for a wide range of modules, necessitating cutting-edge magnetic speed sensors that accurately measure and report wheel speed. Electrical parking brakes need to know if a car moves even an inch when it’s not supposed to. Tire pressure monitoring systems (iTPMS) use complex algorithms to determine if a wheel lacks air pressure. Central locking locks the doors after a couple of meters of movement. Car radios turn up the volume in conjunction with increased speed. These are all examples of where magnetic wheel speed sensors are now required to relay accurate data so that various other modules can operate. 

Our best-selling TLE4941plusC magnetic speed sensor is an industry standard for wheel speed sensing. The similar TLE4942-1C and TLE4943C complement this sensor by reporting additional direction information via pulse-width modulation (PWM) or AK protocols respectively. As a single-chip magnetic wheel speed sensor, it measures the car’s wheel speed magnetically using Hall-effect technology. It’s the ideal all-purpose magnetic speed sensor, equally effective for pole wheel and steel wheel applications. Their differential principles immunize these sensors from undesired magnetic stray fields, ferromagnetic particles, or other disturbances.

The TLE5045/46iC is Infineon’s next-generation magnetic wheel speed sensor family that is based on giant magneto-resistive (GMR) technology. This family includes the designed-to-cost, speed-only TLE5045iC and the high-end TLE5046iC, which not only provide direction detection but also offer true “zero-speed” and self-diagnostic capabilities. This family of speed sensors provides all wheel speed sensing applications in the same package, including sensitivity, jitter, and duty cycles.

Transmission speed sensors

Infineon’s differential Hall-effect TLE4953C automatic transmission speed sensor was developed specifically to detect direction and meet the needs of high-end transmission applications. Its jitter performance and high sensitivity lets designers create high-accuracy systems with excellent vibration suppression. Adaptive hysteresis and dynamic self-calibration algorithms ensure outstanding measurement results with fine as well as coarse target wheels. As with other Infineon magnetic speed sensors, the south and north poles can be pre-inducted. The TLE4953 features a current interface and comes in a two-wire package that features an integrated 1.8 nF over-molded capacitor for improved electromagnetic capability (EMC).

The TLE4955 is the most recent family of differential Hall-effect sensors specifically designed to meet the latest transmission vibration suppression requirements. It provides best-in-class vibration suppression for applications that require a two-wire current interface. Our TLE4955 family provides a similar algorithm as well as dynamic self-calibration, jitter, and sensitivity levels. Their main features include the detection of rotation direction, highly accurate speed measurements from zero to 12 kHz, excellent vibration suppression, and a broad operating temperature range, which guarantees accurate speed measurements for both fine and coarse target wheels in the harshest of environments. Designers can choose between different interface protocol versions.

Technological advancements in automobiles have led to magnetic speed sensors being widely used across automotive applications. In addition to Hall-effect wheel speed sensors, automatic transmission speed sensors and magnetic crankshaft speed sensors monitor the rotational speed of an engine’s crankshaft. Engine management systems use this data to control essential engine components, such as the ignition and flow of fuel. Similarly, camshaft speed sensors regulate the relationship between an engine’s pistons and valves, essential for both the injection of fuel into the engine and the release of exhaust.

Relatedly, magnetic speed sensors have seen increased usage in industrial settings, providing rotational speed measurements for a range of applications. Prominent examples include speed sensors that can be used to report back on web processes and robotic arm movements or measure gear and belt speed and positioning.