The magnet does not need to be oriented when using two sensors, and only needs to be roughly oriented when using one sensor because a 0° point can be set during calibration.
The sensors and magnet must be placed so that the sensor voltage output is not clipped or railed at either the north or south pole.
0° and 360° are the same angle; therefore, use 0 as ANGLEbelow and 360 as ANGLEabove in Equation 4.
Although it is possible to measure voltages that are out of the range of the lookup table (either above the max or below the min recorded voltage values), the absolute min and max values are unknown. Therefore, these measurements are unusable for linear interpolation.
The lookup table calibration method can be more difficult to implement when using two sensors than methods that use the arctan2 function for the following reasons:
Exceptions must be coded to account for when Vabove – Vbelow ≈ 0 V in order to avoid dividing by 0.
Data from the nonlinear regions of each sensor output must be avoided.
Calibration data for each sensor must be stored (instead of storing the arctan2 output); therefore:
It is harder to determine which calibration region to use because the voltage from each sensor appears in two different regions of the respective lookup tables.
It is possible that near a calibration boundary line, the data from each sensor is on either side of that boundary.