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The principle of capacitive touch screen


Capacitive touch uses the current sensing of the human body to work. The capacitive touch screen is a four layer composite glass screen, the inner surface and the interlayer of the glass screen are coated with a layer of ITO. The outer layer is a thin layer of silica glass protective layer, the interlayer ITO coating is used as the working face, four electrodes are drawn out at the four angles, and the inner layer ITO is the shielding layer to ensure a good working environment.


When the finger touches the metal layer, due to the electric field of the human body, the user and the touch screen surface form a coupling capacitor. For high frequency current, the capacitor is the direct conductor, so the finger draws a very small current from the contact point. The current flows out from the electrodes on the four corners of the touch screen, and the current flowing through the four electrodes is proportional to the distance from the finger to the four angle. Through the accurate calculation of the four current ratios, the controller obtains the position of the touch point.