MagSense™ inductive-sensing is a low-cost, robust solution that seamlessly integrates with existing user interfaces, and is also used to detect the presence of metallic or conductive objects.
Inductive-sensing works on the principle of electromagnetic coupling between a sensor coil and the metal target to be detected. When the metal target enters the electromagnetic field induced by a sensor coil, some of the electromagnetic energy is transferred into the metal target, as shown in the figure below.
Field Coupling Between Sensor and Metal Target
This transferred energy causes a circulating electrical current called an eddy current. The eddy current flowing in the metal target induces reverse electromagnetic field on the sensor coil, which results in a reduction of the effective inductance of the sensor coil.
The sensor coil is placed in parallel with a capacitor. The parallel combination of sensor inductance and the external capacitor is called a tank circuit. The reduction in the sensor coil inductance causes an upward shift in the resonant frequency of the tank circuit, where this shift in frequency changes the amplitude of the signal across the sensor coil. The change in the amplitude of the sensor coil signal is measured by the PSoC® MCU to detect the presence of the metal target in the proximity-sensing distance.