The structure of the capacitive touch screen is mainly to plate a transparent thin-film conductor layer on the glass screen, and then add a protective glass outside the conductor layer. The double glass design can completely protect the conductor layer and the sensor. The capacitive touch screen is plated with long and narrow electrodes on all four sides of the touch screen to form a low-voltage AC electric field in the conductive body.
When touching the screen, due to the electric field of the human body, a coupling capacitor is formed between the finger and the conductor layer. The current from the four-side electrode will flow to the contact. The current strength is proportional to the distance between the finger and the electrode. The controller located after the touch screen is The ratio and strength of the current will be calculated, and the position of the touch point will be accurately calculated. The double glass of the capacitive touch screen not only protects the conductors and sensors, but also prevents external environmental factors from affecting the touch screen. Even if the screen is dirty, dust or oil stains, the capacitive touch screen can still accurately calculate the touch position. The capacitive touch screen is a transparent special metal conductive material attached to the glass surface. When a finger touches the metal layer, the capacitance of the contact will change, causing the frequency of the oscillator connected to it to change. By measuring the frequency change, the touch position can be determined to obtain information. Since the capacitance varies with temperature, humidity, or grounding conditions, its stability is poor and it tends to drift.
How to use multi-touch screen
The infrared multi-touch screen uses the infrared matrix densely distributed in the X and Y directions to detect the operator’s touch action. The infrared multi-touch screen needs to install a circuit board outer frame in front of the display. The circuit board is arranged with infrared emitting tubes and infrared receiving tubes on the four sides of the screen to form a horizontal and vertical cross infrared matrix. When the user touches the screen, the finger will block the horizontal and vertical two infrared rays passing through the position, so the position of the touch point on the screen can be judged. Any opaque object can change the infrared rays on the contacts to realize multi-touch screen operation.
The task of multi-touch can be divided into two aspects of work, one is to collect multiple signals at the same time, and the other is to judge the meaning of each signal, which is the so-called gesture recognition. Compared with touch technology that can only accept single-point input, multi-touch technology allows users to simultaneously touch the display screen in multiple places so that they can stretch and rotate web pages or pictures.
In order to realize the multi-touch function, the multi-touch screen and the single-point touch screen adopt a completely different structure. From the outside of the screen, the single-point touch screen has only a few signal lines (usually 4Pin or 5Pin), while the multi-touch screen has many leads; from the inside, the conductive layer of the single-point touch screen is just a flat panel, and multiple The touch screen is divided into many relatively independent touch units on the tablet, and each touch unit is connected to an external circuit through an independent lead, and all the touch units are arranged in a matrix on the board. In this way, when the user’s finger touches a certain part on the screen, a signal will be output from the corresponding detection line. When the finger moves to another part, the signal will be output from another detection line.
Post time: Jul-16-2021