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What is capacitive touch screen
Time：
2023-10-30 14:42
What is capacitive touch screen?
Capacitive screen to achieve multi-touch, rely on the addition of electrodes of mutual capacitance, simply put, is to divide the screen into blocks, set a group of mutual capacitance modules in each area to work independently, so the capacitive screen can be independent The touch situation of each area is detected, and after processing, multi-touch is simply realized.
Capacitive technology touch screen CTP (Capacity Touch Panel) is to use the human body's current induction to work. The capacitive screen is a four-layer composite glass screen. The inner surface of the glass screen and the interlayer are each coated with a layer of ITO (nano-indium tin metal oxide). The outermost layer is a silica glass protective layer with a thickness of only 0.0015mm, and the interlayer ITO coating As a working surface, four electrodes are drawn from the four corners, 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 electric field of the human body, the user's finger and the work surface form a coupling capacitor. Because the work surface is connected to a high-frequency signal, the finger absorbs a small current, and this current flows from the four corners of the screen respectively. In theory, the current flowing through the four electrodes is proportional to the distance from the finger to the four corners. The controller obtains the position through precise calculation of the ratio of the four currents. It can reach 99% accuracy and has a response speed of less than 3ms.
Touch technology of projected capacitive panel Projected capacitive touch screen is to etch different ITO conductive circuit modules on two layers of ITO conductive glass coating. The etched patterns on the two modules are perpendicular to each other, and they can be regarded as X and Y A slider whose direction changes continuously. Since the X and Y structures are on different surfaces, a capacitive node is formed at the intersection. One slider can be used as the drive line, and the other slider can be used as the detection line. When the current passes through one wire in the driving line, if there is a signal of capacitance change in the outside world, it will cause the change of the capacitance node on the other layer of wire. The change of the detected capacitance value can be measured by the electronic circuit connected to it, and then converted into a digital signal by the A/D controller to allow the computer to perform arithmetic processing to obtain the (X, Y) axis position, and then achieve the purpose of positioning.
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