What are the common faults of capacitive screen industrial tablet computers
Capacitive screens use the current induction of the human body to work. The capacitive touch screen is a four-layer composite glass screen. The inner surface and the interlayer of the glass screen are each coated with a layer of ITO (transparent conductive film). The outermost layer is a thin layer of silica glass protective layer. The interlayer ITO coating serves as the working surface. Four electrodes are drawn on the four corners, and the inner ITO is a shielding layer to ensure a good working environment.
When a finger touches the metal layer, due to the electric field of the human body, the user and the surface of the touch screen form a coupling capacitor. For high-frequency current, the capacitor is a direct conductor, so the finger draws a small current from the contact point. This current flows from the electrodes on the four corners of the touch screen, and the current flowing through these four electrodes is proportional to the distance from the finger to the four corners. The controller obtains the position of the touch point by accurately calculating the proportions of these four currents. .
It is precisely because of this working principle of the capacitive screen that the phenomenon of screen skipping occurs. After understanding the working principle of the capacitive screen, it is easy to know the cause of the "drift" of the capacitive screen. This is probably the reason for the "drift" phenomenon of the capacitive screen. No matter what device it is, when a malfunction occurs, the cause must first be found in order to prescribe the right medicine.
The light transmittance and clarity of the capacitive touch screen is better than the four-wire resistive screen, but the reflection is serious. Moreover, the four-layer composite touch screen of the capacitive technology has uneven light transmittance to light of each wavelength, and there is a problem of color distortion. More insulating media will not respond when touched with gloved hands or holding non-conductive objects. The main disadvantage of the capacitive screen is drift: when the ambient temperature and humidity change, and the environmental electric field changes, it will cause the capacitive screen to drift and cause inaccuracy.
Capacitive screens mainly include self-capacitance screens and mutual-capacitance screens. The more common mutual-capacitance screen is an example. The interior is composed of driving electrodes and receiving electrodes. The driving electrodes emit low-voltage and high-frequency signals that are projected to the receiving electrodes to form a stable current. When the human body touches the capacitive screen, because the human body is grounded, the finger and the capacitive screen form an equivalent capacitance, and high-frequency signals can flow into the ground through this equivalent capacitance. In this way, the amount of charge received at the receiving end is reduced, and When the finger is closer to the transmitting terminal, the electric charge decreases more obviously, and finally the touched point is determined according to the current intensity received by the receiving terminal.