Capacitive touch screens need to achieve multi-touch, relying on the electrodes to increase mutual capacitance. Simply put, the screen is divided into blocks. Each set of mutual capacitance modules is working independently in each area, so the capacitive screen can independently detect the touch situation of each area., after processing, multi-touch is simply implemented.
Capacitive Touch Panel CTP (Capacity Touch Panel) uses the current sensing of the human body to work. The capacitive 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 (nano-indium tin oxide). The outermost layer is a 0.0015mm thick bauxite protective layer with an interlayer ITO coating. As the working surface, four corners 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, due to the human body electric field, the user's finger and the working surface form a coupling capacitor. Because the working surface is connected with a high frequency signal, so the finger absorbs a small current that flows out of the electrodes at the four corners of the screen.And theoretically the current flowing through the four electrodes is proportional to the distance from the finger to the four corners.The controller derives the position by precise calculation of the ratio of the four currents.It can achieve 99% accuracy with a response speed of less than 3ms.