Comparison of Magnetic Field Sensor Technologies for the use in Wheel Speed Sensors

The measurement of the rotational speed and angle of a rotating shaft is one of the most frequently used measurement in all fields of mechanical engineering. Different sensing principles, such as optical or magnetic, are commonly used. However, magnetic based sensors offer highest robustness to harsh and dirty environments and are therefore the preferred solution in automotive applications. Even if magnetic based speed sensors exist since decades, their performance is continuously improved and adjusted to the different applications. The paper introduces the sensing arrangement for speed measurement of a rotating shaft. The state of the art magnetic sensing technologies, which are Hall, AMR (anisotropic magnetic resistance), GMR (giant magnetic resistance) and TMR (tunneling magnetic resistance), are described and their limitations are shown. In addition, the recently developed high-linearity-TMR is introduced. The key parameters of the evaluated sensing technologies are compared to each other. The result shows that the recently developed high-linearity-TMR (tunneling magnetic resistance) sensing technology offers the best overall performance.