Position sensors are used in detection and processing of measurement data on the basis of position of a moving object. In this case, the inductive position sensors will measure the angular positions with the use of arising variations of the magnetic field amplitudes.
Rotations or shifts of the moving magnet induce such amplitudes. However, there are disadvantages for such a traditional solution, which include the costs of the magnet, limit of operating temperature, and sensitivity of the magnetic stray fields.
Application of inductive position sensor ASIC
There is a need for position sensors nowadays particularly in the automotive industry. These include the accelerator pedal sensors, gearbox control position sensors, head lamp position sensors, steering angle sensors, turbocharger actuator systems, and throttle body position sensors, among others.
Potentiometers traditionally equip such sensors, but with the reliability disadvantages of mechanical contact sensors In modern cars, such potentiometers are replaceable with electronic contactless sensors on the basis of different principles, such as hall sensors, inductive sensors, or magneto-resistive sensors.
Composition of inductive sensors
An inductive contactless sensor consists of a rotor or cursor and a stator. The rotor or cursor is a passive element designed in a special geometry with a single closed winding. The stator has an excitation coil, electronics, and receiver coils for signal processing.
Development of inductive sensor ASIC
Contactless, magnet-free, inductive position sensors can take advantage of ASIC. These sensors use the physical induction principles in a wire loop and eddy currents for detecting the position of an electro-conductive target. This will glide or rotate over a set of receiver coils.
The sensor has a structure of PCB coils and a target having specifically formed layers from conductive material. Each of the coils is part of the oscillating circuit stimulated by the high-frequency sinus signal.
The magnetic field results in the induction of eddy currents in the metallic target and the opposing field reduces the inductance of the coil. So, both the amplitude of the oscillating circuit and the phase are changing.
The described effect differs and a signal emits from the ASIC that is proportional to the conductive material’s surface. But this depends on the influence of the surface of the conductive material to the coil.
Two coils comprise a sensor element in which each is a part of an oscillating circuit. A phase difference between the resonance signals can be measured from the ASIC when the said coils are influenced asymmetrically by the conductive material of the target.
This phase difference as well as the resulting output signal is sensitive towards the electrical and magnetic influences.
The harsh automotive environment is manageable through an inductive position sensor. This is possible by providing a powerful solution in comparison to other concepts. This type of sensor can be very precise without any contact between the stator and the moving part.
This is quite suitable for applications with frequent sensor movements even if an exceptional accuracy is of need. The sensor ASIC is configurable as a dual, fully redundant system for the purpose of safety relevant applications.
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