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The Introduction Of Capacitive Touch Screen

The Introduction Of Capacitive Touch Screen

Apr 17, 2017

The structure of capacitive touchscreen is mainly coated with a transparent film layer on the glass screen, and a protective glass is added to the conductor layer, and the double glass design can thoroughly protect the conductor layer and the inductor.

Capacitive touchscreen is coated with a narrow electrode on the four sides of the touchscreen, forming a low-voltage AC electric field in the conductive body. When touching the screen, because of the human electric field, the finger and the conductor layer will form a coupling capacitance, the four-sided electrode emitted currents will flow to the contact point, and the current strength of the finger to the electrode is proportional to the distance, located on the touch screen controller will calculate the current ratio and strength, accurately calculate the position of the touch point. Capacitive touch screen double glass can not only protect the conductor and sensors, more effectively to prevent external environmental factors to touch screen, even if the screen stained with dirt, dust or grease, capacitive touch screen can still accurately calculate the touch position.

Because the capacitance varies with temperature, humidity or grounding, the stability of the capacitor is poor, and the drift phenomenon is often produced. This kind of touchscreen is suitable for debugging stage of system development.

Capacitive touchscreen's transmittance and clarity are superior to four-wire resistive screens, of course, and surface acoustic waves and five-wire resistor screens are not comparable. Capacitive screen reflective serious, and, capacitance technology of four-layer composite touch screen to each wavelength of light transmittance uneven, there is a problem of color distortion, because of the light in the reflection of the layers, but also caused the image character Blur.

Capacitance screen in principle of the human body as a capacitor element of the use of electrodes, when a conductor near the sandwich and Ito face coupling between the capacitance of sufficient capacity, the flow of current is enough to cause the wrong action of the capacitance screen.

We know that the capacitance value, although inversely proportional to the distance, is proportional to the relative area, and also related to the dielectric coefficient of insulation. Therefore, when a large area of palm or hand-held conductor near capacitive screen, rather than touching, can cause the capacitive screen misoperation, in humid weather, this situation is particularly serious, hand-held monitors, palm close to the monitor 7 cm or body close to the monitor 15 centimeters can cause a capacitive screen error. Another disadvantage of capacitive screens does not react when wearing gloves or touching a non-conductive object because it adds more insulating media.

The main disadvantage of capacitive screens is drift: when the ambient temperature and humidity change, the environmental electric field changes, will cause the capacitance screen drift, causing inaccurate. For example: The display temperature rises after the boot will cause drift: the user touches the screen while the other hand or side of the body near the monitor will drift; capacitive touchscreen near the larger object moved back to drift, you touch when someone surrounded by watching will also cause drift; the cause of the drift of the capacitance screen belongs to the technical deficiency, the environmental potential surface (including the user's body) although the capacitive touch screen is far away, but more than the finger area, they directly affect the touch position determination.

In addition, theoretically many should linear relations are actually nonlinear, such as: different weight or finger wetting degrees of different people suck the total electricity flow is different, and the total electricity flow changes and the four-point distribution of the change is nonlinear relations, the capacitive touchscreen adopts the four corners of the custom polar coordinates without the origin of the coordinates, the drift after the controller can not detect and recover, and, after 4 A/d complete, by the value of four points flow to the touch point in the right angle coordinate system X, The computational process of y-coordinate values is complex. Because there is no origin, the capacitive screen drift is cumulative, at the workplace also often need calibration. Capacitive touch screen The outermost silica protection glass is very good to scratch. But afraid of nails or hard knocks, knocking out a small hole will hurt the sandwich Ito, whether it is injured and sandwich ito or the installation of the transport process of slander and the inner surface ITO layer, capacitive screen will not work properly.