12 inch touch screen for raspberry pi.Capacitive touch screens have better light transmittance and clarity than four-wire resistive screens, and of course they cannot be compared with surface acoustic wave screens and five-wire resistive screens. Capacitive screens have serious reflections. In addition, the four-layer composite touch screen of capacitive technology has non-uniform transmittance of light at various wavelengths, and there is a problem of color distortion. Due to the reflection of light between the layers, the image characters are blurred. The capacitive screen uses the human body as an electrode of a capacitor element in principle. When a conductor is close to the sandwich ITO working surface and a sufficient amount of capacitance is coupled, the flowing current is sufficient 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 it is also related to the dielectric coefficient of the dielectric. Therefore, when a large area of ??the palm or a hand-held conductive object approaches the capacitive screen instead of touching it, it can cause the capacitive screen to malfunction. This situation is particularly serious in humid weather. Hold the display with your hand and the palm 7 cm away from the display. Within or within 15 cm of the body near the display can cause malfunction of the capacitive screen. Another disadvantage of capacitive screens is that they do not respond when touched with a gloved hand or a non-conductive object, because of the addition of a more insulating medium. The more major disadvantage of capacitive screens is drift: when the ambient temperature and humidity change, and the environmental electric field changes, it will cause the capacitive screen to drift, causing inaccuracies. For example: the temperature rises after the monitor is turned on, it will cause drift: when the user touches the screen, the other hand or the side of the body near the monitor will drift; the larger object near the capacitive touch screen moves back and drifts. Will cause drift; the reason for the drift of the capacitive screen is technically inherent. Although the environmental potential surface (including the user's body) is far away from the capacitive touch screen, it is much larger than the area of ??the finger. They directly affect the determination of the touch position . In addition, in theory, many relationships that should be linear are actually non-linear, such as: the total amount of current drawn by people with different weights or different degrees of wetness of their fingers is different, and the changes in the total amount of current and the changes in the four sub-current amounts It is a non-linear relationship. The custom polar coordinate system of the four corners used by the capacitive touch screen does not yet have an origin on the coordinates. The controller cannot detect and recover after the drift. The calculation process from the flow value to the X and Y coordinate values ??of the touch point on the rectangular coordinate system is complicated. Because there is no origin, the drift of the capacitive screen is cumulative, and calibration is often required at the work site. The outermost silicon protective glass of the capacitive touch screen has good scratch resistance. However, it is afraid that a small hole will hurt the sandwich ITO if it is struck by nails or hard objects. Whether it is the sandwich ITO or the damage during installation and transportation, The inner surface of the ITo layer will not work properly. IQTouch K interactive touch screen feature 20-point touch and dual system -- Android 8.0 system and optional OPS Windows 10Pro system. Its 4K UHD resolution facilitates presentations and collaboration. With optional multi-screen casting software, IQClass 6.0 and installation-free IQClass Plus software, IQTouch K Series can help create an interactive and collaborative teaching atmosphere in class.