As factories and vehicles become more automated, accurate and low-latency sensing of motor shaft speed and position is critical for process control, system reliability, and safety. To address these needs, designers require angular rotation sensors that are fast and precise, with the flexibility to address magnetic field variations and axial misalignment. Complicating the issue for designers are ever-present cost and time pressures, as well as the nature of the operating environments for industrial and automotive applications, which can be challenging in terms of chemicals and oils, as well as temperatures and EMI. Other considerations include wear and tear and ever-changing configurations, which require a degree of flexibility within the sensing device. This article describes the role of angle sensors and shows how position sensing features such as speed and low latency can be customized using specific combinations of magnetic input and sensor element. Sample sensor solutions from AKM Semiconductor, Infineon Technologies, and Monolithic Power Systems are then introduced, and their implementation discussed.
The role of angle sensors Angle sensors are used to sense motor shaft position and speed variations for steering angle sensing for automobiles and high-precision control in robotic systems. They determine the absolute angular position of a diametrically magnetized cylinder on a rotating shaft by detecting the orientation of an applied magnetic field and measuring its sine and cosine components. As the shaft may be rotating at high speed, it’s critical that the data from the sensor be acquired and processed quickly, with minimal latency. One of four magnetic technologies are typically used: Hall effect, anisotropic magnetoresistance (AMR), giant magnetoresistance (GMR), and tunnel magnetoresistance (TMR) (Figure 1). When using any of these technologies, designers must first determine a suitable distance from the magnet surface to the sensor based on specific parameters such as magnetic properties, sensor specification, and assembly tolerances.
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