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What are the classifications of projected capacitive touch screens?
Time：
2023-11-16 14:28
Projected capacitive touch screen is divided into two types: self-capacitive touch screen and mutual capacitive touch screen. Taking the common mutual capacitive touch screen as an example, the interior is composed of driving electrodes and receiving electrodes. The driving electrodes send low-voltage high-frequency signals to the receiving electrodes to form a stable current. When the human body touches the capacitive touch screen, due to the grounding of the human body, the finger and the capacitive touch screen form an equivalent capacitor.
Mutual capacitive touch screen
The mutual capacitive touch screen also uses ITO to make horizontal electrodes and vertical electrodes on the glass surface. The difference between it and the self-capacitive touch screen is that a capacitor will be formed where the two sets of electrodes intersect, that is, the two sets of electrodes form the two poles of the capacitor respectively. When a finger touches the 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 the mutual capacitance is detected, the transverse electrodes send out excitation signals in sequence, and all the longitudinal electrodes receive signals simultaneously, so as to obtain the capacitance value of the intersection of all the transverse and longitudinal electrodes, 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. So, even if there are multiple touch points on the screen, the real coordinates of each touch point can be calculated.
The difference between mutual capacitive touch screen and self capacitive touch screen
The advantage of mutual capacitive touchscreens is that there is less wiring, and differences between multiple contacts can be identified and distinguished simultaneously. Self-capacitance touchscreens can also sense multiple contacts, but cannot distinguish them due to the blurring of the signals themselves. In addition, the sensing scheme of the mutual capacitance touch screen has the advantages of high speed and low power consumption, because it can measure all nodes on the driving line at the same time, so the number of acquisition cycles can be reduced by 50%. This two-electrode structure has the function of self-shielding external noise, which can improve the signal stability at a certain power level.
capacitive touch screen classification
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