What is a capacitive touch screen

Capacitive touch screen technology works by utilizing the current induction of the human body. A capacitive touch screen is a four layer composite glass screen. The inner surface and interlayer of the glass screen are coated with a layer of ITO, and the outermost layer is a thin layer of silica glass protective layer. The interlayer ITO coating serves as the working surface, and four electrodes are led out at the four corners. The inner ITO layer is a shielding layer to ensure a good working environment.
When a finger touches a metal layer, due to the human electric field, a coupling capacitor is formed between the user and the touch screen surface. For high-frequency currents, the capacitor is a direct conductor, so the finger sucks away a very small current from the contact point. This current flows out from the electrodes on the four corners of the touch screen, and the current flowing through these four electrodes is proportional to the distance from the finger to the corners. The controller calculates the position of the touch point by accurately calculating the ratio of these four currents.