Capacitive touch screen for multi-touch
Time:2023-05-20
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The interior of a capacitive touch screen is composed of a driving electrode and a receiving electrode. The driving electrode emits a low voltage and high frequency signal, which is projected onto the receiving electrode to form a stable current. When the human body contacts the capacitive screen, due to the grounding of the human body, the finger and the capacitive screen form an equivalent capacitance.
High frequency signals can flow into the ground through this equivalent capacitance, thus reducing the amount of charge received by the receiving end. When the finger approaches the emitting end, the decrease in charge is more pronounced. Finally, the contact point is determined based on the current intensity received by the receiving end.
As for multi touch, simply put, the screen is segmented. Each group of mutual capacitance modules in each area works independently, and the capacitive screen can independently detect the touch situation in each area. After processing, it can achieve multi-point touch.
The touch screen CTP (capacitive touch screen) uses a current sensor from the human body. Ruixiang digital capacitive screen is a four layer composite glass screen. The inner surface and middle layer of the glass screen are respectively coated with ito (nano indium tin oxide).
The outer layer is a 0.0015 mm thick quartz glass protective layer, the middle layer is coated with an ito working surface, four electrodes are formed at the four corners, and the inner layer is a shielding layer to ensure the working environment.
When a user touches a capacitive screen, due to the effect of an electric field, their fingers form a coupling capacitance with the working surface. Due to the high-frequency signal on the working surface, their fingers absorb very small amounts of current, which flows out from the electrodes at the four corners of the screen. The current flowing through the four electrodes is theoretically proportional to the distance from their fingers to the four corners. The response speed is less than 3ms, achieving 99% accuracy.
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