# What Is the Principle of Capacitive Screen Drift

The capacitive touch screen itself is actually a set of precise leakage sensors. Hands with gloves cannot touch it. Due to the use of capacitance, there is a drift phenomenon. Both the capacitive screen and the cathode screen work in the electrical principle. For the multi-point touch, no matter how many points, continuous or discontinuous, it is judged by the center point of the multi-point touch, because the current superposition can not tell who is who, so there is no way.

According to the basic principle, we encounter insurmountable obstacles: the current transparent conductive material ITO - oxidized metal is very fragile, which will be damaged after a few touches, and can not be directly used as a working layer. The problem of materials is still difficult to solve for the moment, so we have to compromise: add a very thin layer of hard glass outside, which obviously can't conduct electricity, and DC can't do it. Switch to high-frequency AC signal, and absorb an AC current by relying on the coupling capacitance formed between people's fingers (across the thin glass) and the working face. This is the origin of the name of "capacitance" of capacitor screen.

The first is "drift", because the way of coupling capacitance is unstable. It is directly affected by temperature, humidity, finger humidity, human body weight and ground dryness, and is also greatly disturbed by large-area objects outside. These directly violate the basic requirements of the absolute coordinate system as the touch screen, and drift is inevitable, Some capacitive touch screens want to solve the drift problem through 25 point calibration method or even 96 point calibration method. The drift is determined by the way the capacitor works. Using dynamic calculation and empirical value look-up table on the single-chip program of the controller can only cure the symptoms rather than the root cause.

The multipoint calibration method was first used for the large screen projection touch panel to eliminate the line Xing distortion corresponding to the coordinates. The line Xing distortion of the capacitive touch screen is also very severe, mainly because the calculation of the capacitive screen is based on the ideal state that the four electric flows are proportional to the distance from the touch point to the four electrodes. In fact, due to the environmental capacitance Due to the influence of line parasitic capacitance and different people's use, this proportional relationship can not be completely line Xing. The multipoint calibration method can only solve the line Xing problem of local distribution, but can not solve the overall drift.

Another price is: the surface is fragile. The outermost layer of extremely thin glass can be very scratch resistant under normal circumstances, but the process requires that it be manufactured under vacuum because it is afraid of hydrogen. Even a little hydrogen will be combined into fragile glass, which will form a small hole with a gentle tap during use, This is fatal for the capacitive touch screen: the area with a diameter of 5cm around the hole cannot be used. The actual vacuum is impossible. This very thin layer of glass has a 5% probability of encountering a product with holes.

The third is the definition. The reflection of capacitor screen is relatively serious, and there are color distortion and image character blur. The transmittance and clarity of capacitive touch screen are better than four wire resistance screen, especially some new products.   Of course, with the progress of technology, its drift has been reduced, which can be used in most occasions, and its products have a wide variety, including ordinary screen, explosion-proof screen, penetrating touch screen and so on.It is often said that the screen drift occurs when using touch-screen mobile phones. In fact, there are many reasons, not just inferior chargers. I hope you can avoid the following use environment in daily use, protect the capacitive screen and make the service life of TA longer.

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