How to choose and use angle sensors for power steering, motors and robotics
Figure 1: When a magnet is rotated on a TMR sensor, the resistance of the sensing element changes with the rotation angle. (Image source: DigiKey)
This air gap must be consistent with parameters such as magnet size and remanence, also known as residual magnetization. Designers must also ensure that air gap variations don’t result in magnetic fields that are either too low or too high. This requires careful consideration of the appropriate magnet for the application’s air gap (Figure 2). That said, angle sensors can support a wide range of spatial configurations and magnetic field strengths, including both off-axis or side-shaft mounting and end- of-shaft configurations. To help accommodate variations, on-chip non-volatile memory is used to store configuration parameters such as reference zero angle position, ABZ encoder settings, and phase information for the motor windings.
Next, the device’s ability to detect various magnetic field strengths allows developers to customize the angle sensor for specific functions like diagnostics and axial movement sensing. The availability of programmable magnetic field strength thresholds also facilitates the implementation of a push or pull button function outputted as two logic signals.
However, while features like speed, low latency and resolution depend on application requirements, safety is at the heart of angle sensor designs. The compliance to functional safety standards further affirms the commitment for accuracy and reliability- conscious automotive and industrial design environments.
Figure 2: Designers can choose a magnet-to-sensor position based on design considerations such as the required level of immunity to external field disturbance and air gap tolerance. (Image source: Monolithic Power Systems)
52
Powered by FlippingBook