How does the contact sensor work?

In the process of using contact sensors, it is found that adjusting the radius of the sensor has a great correlation to the sensitivity of the measurement. Is this related to the principle of calculating force by contact sensors? What do the three orthogonal rings of the contact sensor represent?How is the definition of the contact force of a contact sensor?How do contact sensors determine when objects are in contact? How should the values of the contact sensor parameters be adjusted in use?

Thanks for help.