Scroll wheels are similar to the encoder and linear rotational sensing methods, but the axis of rotation is changed. A common automotive application is volume control, especially on a steering wheel. Hall-effect sensing allows the designer to place the magnet in a sealed cylinder to act as the user interface while the sensor is just placed on a PCB below the wheel. The same linear and encoder implementations can occur here where a sensor is placed in-plane with the magnet. For the linear case, placing the sensor on axis with the magnet can be more difficult so the sensor is less likely to be in-plane or out-of-plane.

The placement of the sensor impacts the magnetic fields seen by the sensor. For the in-plane case, the Z axis of the magnetic field is completely static while the X and Y axis will have different amplitudes. The out-of-plane case can help a designer receive a similar amplitude in the sinusoidal change in magnetic field due to the rotating magnet. Achieving a similar amplitude requires careful position of the sensor as there will be an optimal placement where the magnetic field amplitudes for a given magnet. Simulating the magnetic field for different positions along the path of potential sensor placement can help determine the best location for amplitude matching. While the sensor is moved away from being in-plane with the magnet, the Z axis of the magnetic field will also have start to give a sinusoidal signal.

As show previously, the amplitudes of the out-of-phase case are more similar and can require less scaling to amplitude match before calculating the angle of the magnet. Similar to the dial rotation method, using a 3D linear sensor to read the magnetic field data provides enough information to implement a push button.

The incremental case is not any different from the encoder implementation, but the case can require the sensors be in-plane or slightly offset from the ring magnet. The digital output from the device still has the same behavior as long as the magnetic threshold of the sensor and magnet choice align. This can easily be implemented with a TMAG5110 or TMAG5111 to sense the rotational motion.