What Is a Capacitive Touch Screen?

Capacitive touch screen technology uses the human body's current sensing to work. The capacitive touch screen is a four-layer composite glass screen. The inner surface and interlayer of the glass screen are each coated with a layer of ITO. The outermost layer is a thin layer of silica glass protective layer. The interlayer ITO coating is used as the working surface. Four electrodes, the inner layer of ITO is a shielding layer to ensure a good working environment. When a finger touches the metal layer, due to the electric field of the human body, the user and the touch screen surface form a coupling capacitor. For high-frequency current, the capacitor is a direct conductor, so the finger draws a small current from the contact point. This current flows from the electrodes on the four corners of the touch screen, and the current flowing through the four electrodes is proportional to the distance from the finger to the four corners. The controller calculates the position of the touch point through accurate calculation of the four current ratios. .

After receiving the touch signal, the capacitive touch screen converts the touch data into electrical pulses and sends them to the touch screen control IC for processing. The signal is amplified by a low-noise amplifier LNA, then analog-to-digital conversion and demodulation, and finally sent to a DSP for data processing.

Capacitive touch screens generally have M + N (M columns and N rows) physical capacitive touch sensors. These M + N interleaved sensors make up M * N capacitive sensing points. When the user's finger approaches the touch screen, its capacitance will change accordingly. The interval of the sensors (that is, the distance between adjacent rows or columns) is usually about a few millimeters. This interval distance determines the physical resolution M * N of the touch screen. ^[5]

1. If the user is using a capacitive touch screen , then it is recommended that the user first properly install the driver required for the capacitive touch screen according to the requirements of the relevant manuals when using it for the first time, and then click with his finger on the screen. "Start" / "Program" / "Microtouch Touchware" to run the screen calibration program. After the calibration is completed, the system will automatically store the calibrated data in the register of the controller. You do not need to calibrate the screen after restarting the system.

2. If the capacitive touch screen is operated halfway, the display resolution or display mode of the touch screen is changed again, or if the refresh frequency of the touch screen controller is adjusted by yourself, and you feel that the cursor and the touch point cannot correspond, you must reset the touch screen. The system performs a calibration operation.

3. In order to ensure the normal operation of the touch screen system, in addition to ensuring the correct installation of the system software, you must also remember not to install two or more touch screen drivers on one host. This will easily cause the system to occur during operation. Conflict, which prevents the touch screen system from working properly.

4. When using a resistive touch screen , if it is found that the cursor does not move or can only move in a local area, the user can check whether the touch area of the touch screen is always pressed by other touching objects, such as once the touch screen is touched by the display case or the cabinet case If you hold it down, it is equivalent to a certain point being touched all the time, so the coordinate position feedback to the controller is not accurate.

5. As mentioned earlier, once the system changes the display resolution, adjusts the screen size and the first installation, there will be inaccurate clicks or drifts. You need to start the positioning program that comes with the application to reposition, but in the When positioning, it is better to use a thinner pen or fingertip for positioning, which is more accurate.

6. The surface acoustic wave touch screen requires a higher working environment. It must be operated in a clean, dust-free environment, and the dust on the surface of the touch screen must be cleaned regularly. Otherwise, dust in the air will cover the touch screen. Reflective streaks or transducers can affect the correct positioning of the system.

7. Do not allow water droplets or other soft things to stick to the surface of the touch screen, otherwise the touch screen is likely to mistakenly believe that the surface acoustic wave screen is inaccurate due to hand touch. In addition, when removing dirt on the surface of the touch screen, the user can carefully wipe away from the center of the screen with a soft dry cloth or detergent, or clean the surface of the touch screen with a dry soft cloth dipped in industrial alcohol or glass cleaning solution.

8. If you touch the surface acoustic wave touch screen with your hand or other touching objects, the touch screen response is very slow, which indicates that the touch screen system is probably outdated, the internal clock frequency is too low, or the water droplets on the touch screen surface are moving. To get the touch screen to respond quickly, you must replace or upgrade the system, or use a rag to dry the water droplets on the touch screen surface.

9. Generally, the touch screen uses the serial port for signal transmission, and the signal is taken from the PS / 2 port, while the TPS screen takes power directly from the host power supply. If the indicator light is off, it means that no signal is obtained and the PS / 2 cable on the control box may be broken. If the light is on but not flashing, the control box is broken, so users must replace the control box. If replacing the control box is still not possible, the screen may be pressed too tightly, and the screws around it need to be loosened slightly, because the touch screen is made of special materials, and it is not easy to be damaged. If the serial port is broken or disabled, the driver cannot be installed because the serial port will be automatically searched for when the driver is installed. Even if it can be installed, the mouse will not move or cannot be positioned. It is best not to use a serial mouse to judge the quality of the serial port. The 9 serial ports may be used in different ways for them. If the screen is pressed, or the ground wire is not connected well, it will not be positioned. If some areas cannot be clicked or the response is slow, it may be affected by dust. You need to remove the cover to remove the dust.

10. When a finger touches a certain position of the capacitive touch screen, when the touch screen does not respond, it is likely that the corresponding touch position is inaccurate, and the cursor cannot be positioned correctly, of course. If the cabinet shell presses the touch area, the user can increase the distance between the cabinet and the monitor screen. If the monitor shell presses the touch area, the user can try to loosen the screws of the monitor shell.