Capacitive touch screen is a layer of transparent special metal conductive material pasted on the glass surface. When a finger touches on the metal layer, the capacitance of the contact will change, so that the frequency of the oscillator connected to it will change. By measuring the frequency change, the touch position can be determined to obtain information.
In principle, the capacitive screen uses the human body as an electrode of a capacitor element. When a conductor with a sufficient capacitance is coupled between the conductor and the interlayer ITO working surface, the current flowing away is enough to cause the power panel to malfunction .
The structure of the capacitive touch screen is mainly to plate a transparent film body layer on the resistance screen, and then add a protective glass outside the conductor layer. The double glass design can completely protect the conductor layer and the sensor.
The capacitive touch screen is plated with long and narrow electrodes on all four sides of the touch screen to form a low-voltage AC electric field in the conductive body. When touching the screen, due to the electric field of the human body, a coupling capacitor will be formed between the finger and the conductor layer. The current from the four electrodes will flow to the contact, and the current is proportional to the distance from the finger to the electrode. The controller behind the touch screen will It will calculate the proportion and strength of the current, and accurately calculate the position of the touch point. The double glass of the capacitive touch screen can not only protect the conductor and the sensor, but also effectively prevent the external environmental factors from affecting the touch screen. Even if the screen is stained with dirt, dust or oil stains, the capacitive touch screen can still accurately calculate the touch position.
Capacitive touch screen is a layer of transparent special metal conductive material pasted on the glass surface. When a finger touches on the metal layer, the capacitance of the contact will change, so that the frequency of the oscillator connected to it will change. By measuring the frequency change, the touch position can be determined to obtain information. Because the capacitance varies with temperature, humidity, or grounding conditions, its stability is poor, and drift often occurs. This kind of touch screen is suitable for the debugging stage of system development.
Defects of capacitive touch screen
Capacitive touch screens have better light transmittance and clarity than four-wire resistive screens. Of course, they cannot be compared with surface acoustic wave screens and five-wire resistive screens. The capacitive screen is seriously reflective, and the four-layer composite touch screen of the capacitive technology has uneven transmittance of light of various wavelengths, and there is a problem of color distortion. Due to the reflection of light between the layers, the image characters are also blurred.
The capacitive screen uses the human body as an electrode of a capacitor element in principle. When a conductor with a sufficient capacitance is coupled between the conductor and the interlayer ITO working surface, the current flowing away is enough to cause the capacitive screen to malfunction. .
We know that although the capacitance value is inversely proportional to the distance between the poles, it is proportional to the relative area, and is also related to the insulation coefficient of the medium. Therefore, when a large-area palm power supply IC or a hand-held conductor is close to the capacitive screen instead of touching it, it can cause malfunction of the capacitive screen. This situation is especially serious in wet weather. Within 7 cm of the rectifier transformer or within 15 cm of the body close to the display can cause malfunction of the capacitive screen. Another disadvantage of the capacitive screen is that it does not respond when touched with gloved hands or non-conductive objects, because of the addition of a more insulating medium.
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