If you go to a modern mobile phone store and get acquainted with the products offered, then the specifications for most devices in the windows will indicate: "Screen type - capacitive." For those who often change mobile communication devices, this term is well known, but what if a person did not seek to buy everything new, preferring proven solutions?
He can only guess: "Capacitive screen - what is it?"
Data Entry Technology
The principle of touch typing is now used everywhere. For example, ATMs or devices for making various types of payments, on the panels of which there are a minimum of buttons, and the required numbers are entered by clicking on the corresponding image, can be found in almost every large store. Capacitive screens were first proposed back in the 1970s, but they did not gain popularity due to the insufficient accuracy of recognition of the pressure zone and the complexity of implementation. But work to improve this solution continued.
Sensors in phones
When models of mobile communication devices with large screens appeared, the question of ergonomics immediately arose. Of course, it could have been reduceda small block of buttons, but this would affect the usability in the most negative way. Compromise solutions were used - the so-called "sliders", but this made the device too thick and made it less reliable due to the need to use a mechanical movable connection. Manufacturers began looking for a solution. And it was found. They turned out to be touch screens, by that time significantly improved and ideally suited for phones.
Resisting pressure
The first models of such screens were made according to the resistive principle. Due to a number of features, such sensors are still used today. Structurally-resistive screen consists of two completely transparent plates: the outer one, which is pressed, is made flexible, and the inner one, on the contrary, is rigid. The space between them is filled with a transparent dielectric material. A conductive layer is deposited on both plates from the inside by sputtering. It is connected in a special way by conductors to the controller, which constantly supplies low voltage to the layers. All this "sandwich" is fixed on the main display. When a person presses on a section of the screen, the plates touch at a certain point, a current is generated. By determining the resistance values along the two Cartesian axes, it is possible to find out with sufficient accuracy exactly where the pressing occurred. This data is transferred to the running program, which then processes it.
Resistive sensors are inexpensive toproduction, excellent performance at low temperatures.
Capacitive screens
Sensors operating on the capacitive principle are much more perfect. Touchpads in laptops are a prime example of such solutions. On foreign sites, in the characteristics of phones with this technology, “Capacity” is indicated. Unlike the resistive solution described above, mechanical pressing is completely irrelevant here. In this case, the property of the human body to accumulate an electric charge is used, acting as a classic capacitor. Capacitive screens are more durable, have excellent "responsiveness". There are two implementation methods: surface and projection. In the first case, a transparent layer of conductive material is applied to the surface of glass or plastic. It constantly has an electric potential from the controller. It is enough to touch the point of the screen with your finger, as the battery leaks into the human body. It can be easily determined, and the coordinates can be transferred to a running program. Projection capacitive screens work differently. Behind the outer glass of the display is a grid of transparent sensor elements (they can be seen at a certain angle and lighting). If you touch the point, then in fact, a capacitor will be formed, one of the plates of which is the user's finger. The capacitance in the circuit is determined by the controller and calculated. This solution allows you to implement the "multi-touch" technology.
