Knowledge

Introduction to Capacitive touch screen



Capacitive touch-screen technology uses the human body's current sensing to work. Capacitive touch screen is a four-layer composite glass screen, the inner surface of the glass screen and the interlayer are coated with a layer of ITO, the outermost layer is a thin layers of silica glass protective layer, the sandwich Ito coating as a working face, four angle leads to four electrodes, the inner layer Ito as a shielding layer to ensure a good working environment. When the finger touches the metal layer, because the human field, the user and the touch screen surface to form a coupling capacitor, for high-frequency current, the capacitance is a direct conductor, so the finger from the contact point suction away a very small current. The current flows from the electrodes on the four corners of the touchscreen, and the current flowing through the four electrodes is proportional to the distance between the fingers and the four corners, and the controller obtains the position of the touch point by accurate calculation of the four current ratios.


A capacitive touch screen is a control display that uses the conductive touch of a human finger or a specialized device for input.
 
Unlike resistive and surface wave panels, which can sense input from either fingers or simple styluses, capacitive touch screen panels must be touched with a finger or a special capacitive pen or glove. The panel is coated with a material that can store electrical charges and the location of touch to the screen is signaled by the change in capacitance in that location.
 
When a capacitive panel is touched, a small amount of charge is drawn to the point of contact, which becomes a functional capacitor. The change in the electrostatic field is measured to find the location. In some designs, circuits located at each corner of the panel measure the charge and send the information to the controller for processing. In multi-touch screens, sensors are arranged in a grid to enable more complex input.
 
Input to resistive touch screens works through pressure resulting in two conductive layers being pressed together. In comparison, capacitive touch screens are not affected by outside elements, have high clarity and allow for easier functioning with lighter contact and greater accuracy.