The simple capacitive screen is a four-layer composite glass plate with a layer of ITO material. ITO is an indium tin oxide material that is transparent and conductive enough to make touch screens.
When a finger touches a part of the screen, it forms a coupling capacitance with the ITO material, changing the capacitance at the contact. The four corners of the screen will have wires, and because alternating current can pass through the capacitor, the current from the four wires will flow toward the contact, and the amount of current is related to the distance from the contact. The chip inside the mobile phone can analyze the current in the four corners, and the position of the contact can be obtained through calculation.
A more elaborate capacitive screen is a projective capacitive screen. It USES a ITO array of corroded candles, and these ITO layers are bordered to form multiple horizontal and vertical electrodes. Each part of the ITO unit also has a sensing function.
When a finger touches something, it is coupled with the array capacitance, changing the electric field on the screen. The position of the contact can be perceived by sensors and chips that analyze changes in the current in an electrical situation. Compared with the previous four-angle current capacitive screen, this capacitive screen can realize multi-touch and is more widely used.
A person's finger is a conductor, which affects the capacitive screen, and touching the capacitive screen with an insulating material does not work on the phone. The mobile phone film can also be used, because the finger and ITO layer originally do not need to contact, there is a glass insulation layer in the middle itself, the effect of the insulation film is only a little thick glass, the current can still flow through the finger and screen conductor formed by the capacitor. However, if the gloves are too thick, touch the touch screen and the finger is too far away from the conductor in the screen, the capacitance is too small to be sensed by the sensor, so you can't operate the phone with thick gloves.
In fact, there are many capacitive sensors in life, such as the common toilet automatic flushing device, automatic dry cell phone, many are using capacitive sensing. When the human body is near or far away, the capacitance between the human body and the device changes. The sensor senses this change and controls the circuit to perform certain operations.