A high-frequency magnetic field is generated by coil in the oscillation circuit.
When a target approaches the magnetic field, an induction current (eddy current) flows in the target due to electromagnetic induction.
As the target approaches the BD sensor, the induction current flow increases, which causes the load on the oscillation circuit to increase.
Then, the BD sensor detects this change and know there is a metal object there. if the metal object is away from the coil, the sensor need to increase the current to detect that object.
That’s the reason why the BD sensor knows the distance between metal bed and coil with the different current.
Shield Coil VS PCB Coil:
Compared with PCB coils, shielded coils have the following advantages:
- Higher resolution
- Stronger sense.
- Compatible with complex environments
