Technical analysis of capacitive touch screen
May 02, 2018
Capacitive touch screen technology uses the body's current sensing to operate. The capacitive touch screen is a four-layer composite glass screen. The inside and outside surfaces of the glass screen and the interlayer are respectively coated with ITO. The outermost layer is a thin layer of alumina glass protective layer. The interlayer ITO coating is used as the working surface, and the four corners lead out. Four electrodes, the inner ITO shield layer to ensure outstanding working environment.
When the finger touches the metal layer, the user and the touch screen form a coupling capacitor due to the body electric field. With respect to the 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 the four electrodes is proportional to the distance from the finger to the four corners. The controller calculates the position of the touch point after accurate accounting of these four current shares. .
Capacitive Panel Touching Capability The projected capacitive touch screen etched different ITO conductive line modules on two layers of ITO conductive glass coating. The patterns etched on the two modules are straight to each other and can be regarded as sliders whose X and Y directions change continuously.
Because the X and Y architectures look different, their intersections form a capacitive node. One slider can be used as a drive line, and the other as a detection line. When the current passes through one of the wires in the drive line, if the outside world has a signal that the capacitance changes, then the capacitance node on the other wire will change.
The change of the detected capacitance value can be obtained through the electronic loop connected to it, and then converted to a digital signal via the A/D controller so that the calculator can perform an arithmetic operation to obtain the (X, Y) axis azimuth and then reach the target of positioning.
