The principle of capacitive touch screen

Now most of us have cell phones, and the majority of the touch screen is capacitive, and this article we will share something about the principle of capacitive touch screen.

The sensitive screen of capacitive touch screen is a four-layer composite glass screen; the glass screen of the inner surface of the sandwich coated with a conductive layer, the outermost layer is a thin layer of silica glass protective layer. When our fingers touch the surface of the sensitive screen, the electric field of the human body form a coupling capacitor. For high frequency current, capacitance is the direct conductor, so fingers absorb a very small current from contact point. The current points outflow, and flows through to the four corners of the four electrodes and the finger is proportional to the distance from the electrodes on the four corners of the touch screen. Controller gets the location of the touch points through the accurate calculation of the four current ratio.

Compared to traditional resistive touch screen, capacitive touch screen have these advantages as the following aspects:

1. Novel. The capacitive touch screen supports multi-touch operation, so the operation is more intuitive and more fun.

2. It is not easy to inadvertently. The capacitive touch screen need to induce body’s current, only the human body can operate, there will be no reaction when other objects touch it, so basically, avoid the possibility of inadvertently.

3. Durability. Compared to the resistive touch screen, capacitive touch screen in a dust-proof, waterproof, wear better performance.

As a legitimate touch-screen technology, the capacitive touch screen with a gorgeous interface, multi-touch, only the human body sensors and other advantages, but at the same time, it also has the following disadvantages:

1. The accuracy is not enough. For technical reasons, compared to the capacitive touch screen, resistive touch screen is not accurate, which had been lacking. And only use your finger to input, it is difficult to recognize complex locus on small screen handwriting.

2. Vulnerable to environmental impacts. Environmental factors like temperature and humidity changes can also lead to instability of the capacitive touch screen and even drift. Such as a user use the screen and close to the body, the screen may cause drift, even a crowded can also cause drift. This is mainly due to the capacitive touch screen technology works, although the distance from the screen of the user’s finger is closer, but around the screen, there are a lot of volume is much larger than the electric field of the fingers simultaneously, which would affect the judgment of the touch location.

3. Expensive. In addition, there are some technical difficulties of the capacitive touch-screen touch pad attached to the LCD panel, the yield is not high, so virtually, this has also increased the cost of capacitive touch screen.

In the past, due to cost and technical factors, the use of the resistance control panel is far more than the capacitive touch screen technology. But within the last stage, with technological advances and mass, the price of capacitive touch screens are falling, and the price gap with resistive touch screen is getting smaller and smaller. So, the majority of the cell phone manufactures all use the capacitive touch screen.