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What are the categories of projection capacitive touch screens?


Projective capacitive touch screens are divided into two types: self capacitive touch screens and mutual capacitive touch screens. Taking a common mutual capacitive touch screen as an example, the interior is composed of a driving electrode and a receiving electrode. The driving electrode sends low voltage and high frequency signals to the receiving electrode, forming a stable current. When the human body contacts the capacitive touch screen, due to the grounding of the human body, the fingers and the capacitive touch screen form an equivalent capacitor, through which the high frequency signals flow into the ground wire, The amount of electrical charge received by the receiver decreases as the finger approaches the transmitter.

Mutual capacitance touch screen

Mutual capacitance touch screens also use ITO to make lateral and longitudinal electrodes on the glass surface. The difference between them and self capacitance touch screens is that capacitors are formed where the two sets of electrodes intersect, that is, the two sets of electrodes form the two poles of the capacitor. When a finger touches a capacitive touch screen, it will affect the coupling between the two electrodes near the touch point, thereby changing the capacitance between the two electrodes. When detecting the mutual electrical capacity, the transverse electrodes sequentially send out excitation signals, and all the longitudinal electrodes simultaneously receive the signals, thereby obtaining the capacitance values of all the transverse and longitudinal electrode intersections, that is, the capacitance of the entire two-dimensional plane of the touch screen. According to the change data of the two-dimensional capacitance of the touch screen, the coordinates of each touch screen can be calculated. Therefore, even if there are multiple touch points on the screen, the true coordinates of each touch point can be calculated.

Difference between mutual capacitance touch screen and self capacitance touch screen

The advantage of a mutual capacitive touch screen is that it has less wiring and can simultaneously identify and distinguish differences between multiple contacts. Self capacitive touch screens can also sense multiple contacts, but due to the ambiguity of the signal itself, they cannot be distinguished. In addition, the sensing scheme of the mutual capacitance touch screen has the advantages of high speed and low power consumption. Because it can simultaneously measure all nodes on the drive line, the number of acquisition cycles can be reduced by 50%. This dual electrode structure has the function of self shielding external noise, which can improve signal stability at a certain power level.

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