Inductive sensing relies on the interaction of EM fields generated by the inductive sensor and the eddy currents⁽²⁾ being induced on the conductive surface. The amount of eddy currents induced on the target surface decreases with an increase in D_TARGET as the target conductive surface now captures a smaller portion of the electromagnetic field generated by the inductive sensor. In turn, the physical size of electromagnetic field lines generated by an inductive sensing coil is directly proportional to the diameter of the sensor. Figure 1-2 shows how to set D_TARGET as a percentage of the coil diameter for inductive touch.

Figure 1-2 Button Sensitivity as a Function of D_TARGET