Last time we talked about the 8 advantages of the capacitive touchscreens, do the capacitive screen have any disadvantages? What are the shortcomings?
1. The transmittance and clarity of capacitive touchscreens is better than that of four-wire resistor screen, but it can not be compared with surface sound wave screen and five-wire resistor screen. The reflection of the capacitive touchscreens is serious, and the transmittance of the four-layer composite touch screen of capacitance technology to each wavelength is uneven, and there is the problem of color distortion. Due to the reflection of light between the layers, it also causes the blurring of image characters.
2. Current: in principle, the capacitive touchscreens use the human body as an electrode of a capacitor element. When a conductor is close to the capacitance coupled to the sandwich ITO working face, The current flowing away is enough to cause the capacitance screen to misact.
3. Although the capacitance 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 larger palm or handheld conductor is close to the capacitive touchscreens instead of touching, it can cause the capacitive screen to misact, especially in wet weather. Holding the monitor by hand, palm within 7 cm or body within 15 cm can cause the capacitance screen to misact. Another drawback of the capacitive touchscreens is that it does not respond when touched by a gloved hand or a hand-held non-conductive object because of the addition of a more insulating medium.
4. Drift: the main disadvantage of capacitive touchscreens is drift: when the ambient temperature and humidity change, the environmental electric field changes, it will cause the drift of capacitive screen, resulting in inaccuracy. For example, the temperature rise of the monitor after booting will cause drift: when the user touches the screen, the other hand or side of the body will drift near the monitor; The larger object near the capacitive touchscreens will drift after moving, and it will also cause drift if someone comes around to watch it when the user touches it. The reason for the drift of the capacitive screen belongs to the inherent shortcomings of the technology. Although the environmental potential surface (including the user's body) is far away from the capacitive touchscreens, it is much larger than the finger area, and they directly affect the determination of touch position.
In addition, in theory, many of the relationships that should be linear are actually nonlinear. For example, the total current absorbed by people with different weights or different degrees of wetting fingers is different. The relationship between the change of the total current and the four sub-current is nonlinear. The four-angle custom polar coordinate system adopted by the capacitive touchscreens do not have the origin on the coordinates, and the controller can not detect and recover after drift. After the completion of the four A, the calculation process from the values of the four distributions to the X and Y coordinate values of the touch point in the Cartesian coordinate system is complex. Since there is no origin, the drift of the capacitive screen is cumulative and often needs to be calibrated at the work site. The silica protective glass on the outermost surface of the capacitive touchscreens is very resistant to scraping, but it is afraid of knocking out a small hole in the fingernail or hard object, which will hurt the sandwich ITO, whether it is injuring the sandwich ITO or injuring the inner surface ITO layer during installation and transportation. The capacitive touchscreens won't work properly.
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