Capacitive screen working principle

Capacitive screen working principle

In general, the working principle of the touch screen is to report coordinate values, X-axis and Y-axis values. Unlike resistive touch screens, capacitive touch screens do not rely on finger pressure to create and change voltage values to detect coordinates. Capacitive screens work through any object that holds electrical charge, including human skin. (The charge carried by the human body) The capacitive touch screen is made of materials such as alloy or indium tin oxide (ITO), and the charge is stored in a tiny electrostatic net that is thinner than a hair. When a finger taps on the screen, a small amount of current will be absorbed from the contact point, causing a voltage drop in the corner electrode. The touch is achieved by sensing the weak current of the human body.

1. There are two main types of capacitive touch screens:

(1) Surface capacitive type: The surface capacitive type uses sensors located in the four corners and a thin film evenly distributed across the surface. It has a common ITO layer and a metal frame. When a finger touches the screen, it is released from the board. The charge is sensed at the four corners of the touch screen, no complicated ITO patterns are required;

(2) Projected Capacitors: One or more carefully designed, etched ITO layers are used to form multiple horizontal and vertical electrodes through corrosion, and independent chips with interlaced rows/columns with sensing functions are used. Now tablets, mobile phones, vehicles, etc. mostly use projected capacitors, so our later analysis shows the composition of projected capacitors.

Axial coordinate sensing unit matrix of projected capacitance: The separate rows and columns of the axis coordinate sensing unit are realized by two crossed sliders. X-axis slider and Y-axis slider are used to detect the capacitance change of each grid sensing unit.