Surface Capacitive Touch Screen VS Projected Touch Screen

Surface Capacitive Touch Screen VS Projected Touch Screen

The principle of surface capacitive touch screen

Surface capacitive screen, the capacitance value generated by the contact between sensor and human, is not a capacitance value itself, so it is impossible to judge the Z-axis information, the finger must really touch to judge the coordinates.

The surface of the capacitive screen is plated with a transparent conductive layer of ITO, the voltage is connected to the four corners, and the charge is distributed on the surface of the screen, forming a uniform electric field, when touching the screen with the hand, the human body will act as a pole of the coupling capacitor, the current is gathered from the four corners of the screen, and then another pole of the coupling capacitor is formed, and the controller can calculate the relative distance from the current to the touching position, so as to get the accurate coordinates value. Surface capacitive touch screens can only be touched directly with the finger, while projected capacitive touch screens can penetrate through tempered glass!

The principle of projected capacitive screens

Projected capacitive sensing principle is divided into self-capacitance and mutual capacitance, self-capacitance is the X, Y electrodes of the ITO Pattern, itself has a parasitic capacitance, forming a relatively uniform plane of multiple sensing unit capacitance, when the finger to contact, the capacitance of each sensing unit is detected in the change, so as to obtain the coordinates. The mutual capacitance detects the change of coupling capacitance at the intersection of X and Y electrodes, so both of them have multiple capacitance of induction units, and the capacitance change caused by the finger is used for positioning, so the distance between the finger and the panel can be distinguished, i.e., the information of Z-axis can be provided. Even if the user is wearing gloves or the sensor has a 5mm thick glass on the outside, it can be the same action.

Projected capacitive screen is the use of projected capacitive touch technology screen, the touch screen panel can detect the change in capacitance of its position before the finger touches, and then calculate the location of the finger, and then multi-touch operation.