Capacitive touch screen technology works by utilizing the human body's current sensing. The capacitive touch screen is a four layer composite glass screen. The inner surface and interlayer of the glass screen are respectively coated with a layer of ITO. The outer layer is a thin protective layer of quartz glass, and the interlayer ITO coating serves as the working surface. Four electrodes are introduced from the four corners, and the inner layer ITO serves as a shielding layer to ensure a good working environment. When fingers touch the metal layer, considering the electric field of the human body, coupling capacitance is formed between the user and the touch screen surface. Compared to high-frequency current, capacitors can be direct conductors, so the current drawn by fingers from the contact point is very small. This current is mainly discharged from the electrodes on the four corners of the touch screen, and the current flowing through these four electrodes is positively correlated with the distance from the fingers to the four corners. The controller accurately calculates the ratio of these four currents and draws conclusions about the position of the touch points.
When a customer touches a capacitive touch screen, considering the electric field of the human body, the user's fingers and working surface form a coupling capacitor. Because the working surface is connected to high-frequency signals, the current absorbed by the fingers is very small, mainly discharged from the electrodes at the four corners of the screen. In theory, the current flowing through the four electrodes is proportional to the distance from the fingers to the four corners, and the controller accurately calculates the proportion of the four currents to obtain the conclusion position. The accuracy can reach 99%, and the response speed is less than 3ms.
The anti-interference problem of capacitive touch screens is a headache. The anti-interference performance of capacitive touch screens is one of the performance requirements of touch screens. If the anti-interference ability is weak, it will affect the touch screen effect of the switch, such as the problem of insensitive and inaccurate touch, which is greatly affected by external factors. How to solve the anti-interference problem of capacitive touch screens?
Firstly, it is necessary to understand the structure and principle of capacitive touch screens, and then identify the reasons for the anti-interference of capacitive touch screens. What are the general effects? The anti-interference problems of capacitive touch screens include the following: screen skipping, inaccurate touch, or complete failure. Then determine whether there are external factors, such as untimely power supply, weak signal, weak antenna signal, etc. These are all common, just check if there are any of the above phenomena before making adjustments.
So, in order to solve the anti-interference problem in the design of capacitive touch screens, the following adjustments must be made: first, add virtual wiring in the blank area of the touch screen panel, that is, fill the wiring outside the display area, and connect the added virtual wiring with each other to form a virtual circuit; Secondly, the virtual circuit connects the grounding part of the touch chip to form a shielding circuit. This design eliminates interference from factors such as temperature, humidity, environmental electric field, and reflection on capacitive touch screens, resulting in low cost and high efficiency.
