FAQ

What are the differences between capacitive touch and resistive touch on a touch all-in-one?

Source: KONWHAI TOUCHAuthor: KONWHAI Date: 2019-12-23 Click:

  •      Touch screen, also known as "touch screen" and "touch panel", is an inductive liquid crystal display device that can receive input signals such as contacts. When the graphic buttons on the screen are touched, the tactile feedback system on the screen can Various connected devices are driven according to pre-programmed programs, which can be used to replace mechanical button panels, and produce dynamic audio and video effects through the LCD display screen.
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  •      As a newest computer input device, touch screen is the simplest, most convenient and natural way of human-computer interaction. It gives multimedia a new look and is a very attractive new multimedia interactive device. It is mainly used for public information query, leadership office, industrial control, military command, video games, song and order, multimedia teaching, real estate pre-sale, etc.
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  •      At present, the use range of touch all-in-one is quite wide. Technically, the touch screen is a transparent absolute positioning system. It must have three characteristics: transparent performance, absolute coordinate system, detection and positioning. In the market, the touch all-in-ones generally use two methods, infrared and capacitive touch, but in fact, there is also a resistive touch screen. So what is the difference between the three?
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  • What are the differences between capacitive touch and resistive touch on a touch all-in-one?
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  •   Analysis of the characteristics of three touch screens: 
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  • 1.Resistance screen
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  •      The resistor is made of two layers of dielectric and is triggered by the pressure of the object on the surface, so its advantages are high resolution and low cost. The disadvantage is that it has a short life and is afraid of scratches on the surface, so it is not suitable for self-service equipment used in public places. It is more suitable for terminal equipment or industrial control terminals such as industrial control terminals, handheld terminals, tablet computers, and home appliances. Touch displays, etc .; At present, the resistive touch screen of a touch all-in-one on the market is actually a sensor that converts the physical position of a touch point (X, Y) in a rectangular area into a representative of X and Y coordinates Voltage.
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  •      Many LCD modules use resistive touch screens. This screen can use four-, five-, seven-, or eight-wires to generate a screen bias voltage and read back the voltage at the touch point. The resistive touch screen basically has a structure of a thin film and glass, and an adjacent surface of the thin film and the glass is coated with an ITO (nano indium tin metal oxide) coating. ITO has good conductivity and transparency.
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  •      When touch operation is performed, the ITO on the lower layer of the film will contact the ITO on the upper layer of the glass, and the corresponding electric signal will be sent out through the sensor, which will be sent to the processor through the conversion circuit, which will be converted into the X and Y values ​​on the screen by calculation, and the completion point The selected action is displayed on the screen. Therefore, the resistance screen is cheaper and can adapt to a variety of harsh environments. Under any circumstances (such as going to the toilet, bathing, sauna), in any environment (such as rain, snow, high temperature, ultra low temperature), use anything ( (Such as nails, toothpicks, lighters, tongues) can accurately touch the resistance screen.
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  • 2.Infrared screen
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  •      The infrared screen determines the focus by infrared ray cross-induction on the four sides around the screen body, so it is dustproof, waterproof, anti-scratch and anti-riot, supports multi-touch, suitable for harsh environments, and is not restricted by the size of the screen body. It is more suitable for large screens. The disadvantage is that it is too sensitive. Because it is affected by infrared rays, it often feels that your finger has not touched the screen, and the screen response has already occurred.
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  •      The infrared touch screen uses a dense infrared matrix in the X and Y directions to detect and locate the user's touch. The infrared touch screen is equipped with a circuit board frame on the front of the display. The circuit board arranges infrared transmitting tubes and infrared receiving tubes on the four sides of the screen, which correspond to the infrared matrix that crosses vertically. When the user touches the screen, the finger blocks the two infrared rays passing through the position, so that the position of the touch point on the screen can be determined.
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  •      Infrared touch screen is a highly integrated electronic circuit integration product. The infrared touch screen contains a complete integrated control circuit, a set of high-precision, anti-interference infrared transmitting tubes and a set of infrared receiving tubes. The two opposite directions installed on the highly integrated circuit board form an invisible infrared Raster. The intelligent control system embedded in the control circuit continuously pulses the diode to form an infrared polarization beam grid.
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  •      When a touch object such as a finger enters the grating, the light beam is blocked. The intelligent control system will detect the change in the loss of light and transmit a signal to the control system to confirm the X-axis and Y-axis coordinate values. As shown in the figure below, it is a custom-made infrared touch all-in-one machine with a groove, not a pure plane.
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  • 3. Capacitive screen
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  •      Capacitive screens rely on the human body's electric field to trigger events, so the triggering is extremely sensitive, and supports multi-touch, but does not accept the touch of other insulating objects. Fingers are more commonly used, and the external environment has a greater impact on them, such as weather, air humidity, and The magnetic field interference of other objects, so it is not suitable for large screens in public places, only suitable for mobile phones or tablet computers used by someone. The capacitive touch screen uses the human body's electricity to work. Its touch screen is composed of a four-layer composite glass screen, and a layer of transparent special metal conductive material is pasted on the surface.
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  •      When a finger touches the touch screen, since the human body's electric field, the user and the touch screen surface 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 the four electrodes is proportional to the distance from the finger to the four corners. The controller calculates the position of the touch point through accurate calculation of the four current ratios. 
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  •      The capacitive touch all-in-one machine can be multi-touched. Now the multi-touch capacitive screen used on IP can only achieve two-point simultaneous touch, which will later develop into three points, four points, and N points. It is not to say that the capacitive touch all-in-one is not defective. Relatively speaking, the main disadvantage of capacitive screens is drift: when the ambient temperature and humidity change, and the environmental electric field changes, it will cause the capacitive screen to drift, causing inaccuracies. 
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