As previously mentioned, the magnet for the design needed to be 1/2 inch in diameter while providing enough magnetic flux density to operate near full scale input of the ±100 mT input range. It is best to leave headroom in the design to allow for variations, so a rough target of about 90% was chosen to guide magnet selection.

Even within this restriction, there is still a fair amount of flexibility regarding magnet thickness, magnet material, and the air gap between the magnet and sensor. For this diameter magnet, 1/8 in is a common available thickness that is available in multiple material types and is easily handled during assembly.

With a magnet geometry selected, simulations of magnetic flux density for various materials and air gaps were run to determine the remaining variables.

Figure 4-2 Push-Button Knob Proximity Simulation

Based on these results, the N42 material was selected to use at an distance of 3 mm from the sensor.