Capacitive touch screen use the current sensing of human body to work. When a human finger or something special like touch pen touch the screen, it will give a feedback. Capacitive touch screen is a four-layer composite glass screen, and the inner surface and the inter-layer of the glass screen are coated with ITO which can store the electrical charges. The first layer is a thin layer of bauxite for protection, and the inter-layer of glass with ITO is used as working surface.
When a finger touch the screen, a few charges will move to the point of contact. There are four electrode in the glass of inter-layer, and they will measure the charge and send the information to the controller for calculating. After precise calculation, the point can be located.