How does a touch-screen phone work?

Capacitive technology Touch screen The CTP (Capacity Touch Panel) uses the current sensing of the human body. The capacitive screen is a four-layer composite glass screen, with the inner surface sandwich coated with one layer of ITO (nano indium tin metal oxide), and the outermost layer being only 0.01 mm thick silica glass protective layer. The working face is coated with an interlayer ITO coating; four angles lead to four electrodes; and the inner layer of ITO is the screen layer to ensure the working environment.

When the user touches the capacitive screen, the coupling capacitor forms between the user's fingers and the working surface due to the human electric field because of the high connection on the working surface. Frequency signal, so the finger absorbs a small current; the current flows out of the electrodes in the four corners of the screen, and theoretically, the current through the four electrodes is proportional to the distance between the finger and the four corners of the ratio of the four currents. It can reach 99% accuracy with a response speed of less than 3 ms.

The projection capacitive touch screen is etched into different ITO conductive line modules on two layers of ITO conductive glass coating. The etched figures on the two modules are perpendicular to each other, and they can be regarded as continuous changes in the X and Y directions. The slider. Since the X and Y architectures are on different surfaces, a capacitor junction is formed at their intersection. One slider can be used as a driver line, and the other slide can be used as a detection line. When the current passes through one wire in the drive line, if there is a signal of capacitance change outside, it will change the capacitance node on the other layer of wire. The change in capacitance value can be detected by measuring the electronic circuit connected to it, and then through the A/D controller to the digital signal for the computer to obtain the (X, Y) axis position and then reach the positioning.