Working Principle of Capacitive Touch Screen

1. How does the capacitive touch screen work?

The capacitive touch screen working principle uses an indium tin oxide (ITO) sensor. Since the human being is a moving capacitor, the capacitance level perceivable by the system will change when the ITO is touched.

The capacitive touch screen is a four-layer composite glass screen. When a finger touches the metal layer, the user and the surface of the touch screen can form a coupling capacitor due to the human electric field. For high-frequency currents, the capacitor is a direct conductor so that the finger can move from a small current from the contact point. This current flows from the electrodes on the four corners of the capacitive touch screen, and the current flowing through each electrode is proportional to the distance from the finger to the corners. The touch point can be determined by accurately calculating the ratio of these four currents by the controller.

The capacitive screen can achieve the multi-touch function by increasing the electrodes of mutual capacitance. Simply speaking, it refers to dividing the screen into modules and set up mutual capacitors in each area. Each module works independently, so the capacitive screen can independently detect the touch of each area. The multi-touch function can be simply achieved after processing.

2. The capacitive touch screen is favored by consumers for two main reasons:

(1) The capacitive touch screen has two layers of TIO, sometimes only one layer. It uses a checkerboard-like textured sensor so that it can be overlaid with a whole piece of the LCD to achieve a clearer and brighter screen.

(2) Unlike the flexible polyurethane layer of the resistive screen, the safety glass layer can be placed on the top layer for sealing because the capacitive touch screen control uses the electrolytic capacitor method for detection. It also brings a more durable design to users.