Veriton touch screen - an overview and working principle of capacitive touch screen

An overview of the principles

To complete multi-touch on the capacitive screen, it depends on adding electrodes of mutual capacitance, in short, the screen is divided into blocks, and a group of mutual capacitance modules are set up in each area to work independently, so the capacitive screen can independently detect the touch status of each area, and after processing, simply complete the multi-touch.

The operating principle of capacitive contact screens

The Capacitive Skill Touch Panel (CTP) uses the current sensing of the human body to operate. The capacitive screen is a four-layer composite glass screen, the inner and outer surface of the glass screen and the interlayer are each coated with a layer of ITO (nano indium tin metal oxide), the outermost layer is only 0.0015mm thick silica glass protective layer, the interlayer ITO coating is used as the working surface, the four corners lead to four electrodes, and the inner ITO is the screen layer to ensure the working environment. [3]

When the user touches the capacitive screen, because of the electric field of the human body, the user's finger and the working surface constitute a coupling capacitor, because the working surface is connected to a high-frequency signal, so the finger absorbs a very small current, and the current flows out of the electrodes on the four corners of the screen respectively, and theoretically the current flowing through the four electrodes is divided into shares with the interval between the fingers and the four corners, and the manipulator obtains the direction after the precise calculation of the four current shares. It can reach 99% accuracy, with a response speed of less than 3ms.

Projected capacitor panel

The touch skills of the projected capacitive panel The projected capacitive contact screen is etched on two layers of ITO conductive glass coating with different ITO conductive line modules. The etched graphics on the two modules are perpendicular to each other, and they can be seen as sliders that change in succession in the X and Y directions. Because the X and Y architectures are of different appearances, their intersection forms a capacitor node. One slider can be used as a drive line, and the other slider can be used as a detection line. When current passes through one of the wires in the drive line, if there is a signal from the outside world that the capacitance is changing, then it will cause the capacitance node on the other layer of wires to change. The change of the detected capacitance value can be measured by the connected electronic loop, and then converted into a digital signal by the A/D manipulator for the computer to calculate and process to obtain the (X,Y) axis orientation, and then reach the positioning goal.

During operation, the manipulator successively supplies power to the drive line, thus creating a specific electric field between the nodes and the wire. Then, the sensing line is scanned in a row to measure the capacitance change between the electrodes, and then multi-point positioning is achieved. When a finger or traction medium approaches, the controller quickly detects the change in capacitance between the touch node and the wire, and then confirms the direction of the touch. One axis is driven by a set of AC signals, and the response through the contact screen is sensed by electrodes on the other axes. Users refer to this as 'traversal' sensing and can also be referred to as projective sensing. When the finger touches the surface of the touch screen, the capacitance value under the touch point is added according to the distance of the touch point, and the continuous scanning on the sensor detects the change of the capacitance value, and the control chip calculates the touch point and reports it to the processor.

Veriton touch screen - an overview and working principle of capacitive touch screen

Veriton touch screen - an overview and working principle of capacitive touch screen

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