How Position Sensors Enable Innovation in Automotive and Industrial Applications

This paper examines trends in position sensing and associated design challenges and solutions in automotive and industrial applications.

Even if you have been behind the wheel for a while, you probably have not noticed much difference in the steering wheel or even the braking system from one vehicle to another. This is by design. Handling improvements make it easier for drivers, but in general, the feel of these systems has remained relatively the same, in order to ensure that the user experience also remains the same regardless of model year.

The technologies used in these systems have evolved over time, however, and position sensors have been a big part of this evolution.

Many types of position sensors are available today, including ultrasonic, optical, magnetic, capacitive and inductive. Position-sensing integrated circuits (ICs) detect the movement of an object and transduce the input signal into an electrical signal suitable for microcontroller (MCU) processing and control. In the context of this paper, when referring to a position sensor, you can assume that the IC sensor uses Hall-effect, anisotropic magnetoresistor (AMR) or inductive technology. Figure 1 illustrates the basic functionality of these three sensor types.

Figure 1 Hall-effect, AMR and inductor sensor functionality.

In the Hall-effect technology, a current is induced into a ferromagnetic material. Applying a magnetic field (labeled a B field, see Figure 1) produces a Hall voltage perpendicular to the current flow.

An AMR sensor’s resistance decreases with the applied magnetic field. Additionally, the anisotropic aspect means that the AMR sensor is dependent on the direction of the magnetic field applied.

Inductive sensors use sensor coils (inductors) to produce magnetic fields of their own, which couple with the magnetic fields produced by eddy currents developed on metal targets.

This white paper discusses four current trends in position sensing: the electrification of systems, the need for increased reliability and safety, the miniaturization of overall end-product form factors, and the transition from rare earth materials to ferrites. Designers can benefit from understanding the latest in IC sensor improvements, which are now far more accurate and sensitive; able to provide higher resolution and more functionality; and consume less power than before, while being available in ever-smaller packages.

Manny Soltero

At a glance

1 Trend No. 1: The electrification of systems	Position sensors measure complex angles with high accuracy throughout evolving automotive systems, including electric motors and electric power steering (EPS) systems.
2 Trend No. 2: The need for increased reliability and safety	Shifting from mechanical systems to magnetic sensors reduces wear and tear while increasing the need for functional safety.
3 Trend No. 3: The miniaturization of overall end-product form factors	High-sensitivity magnets and greater integration address trade-offs of miniaturization, including lower accuracy and resolution.
4 Trend No. 4: The transition from rare earth materials to ferrites	Ferrite is an abundant and cost-efficient alternative to rare earth materials in magnetic sensors but requires features to compensate for its reduced magnetic field and temperature drift.