Question

Besides capacitive and resistive screens, what other types of screens are there?

Answer 1

With the development of technology, monitors have also begun to have touch control functions, eliminating the need for a mouse and keyboard and becoming more convenient. In industrial production, if a monitor equipped with a touch screen makes operation simpler and more convenient, it will bring higher efficiency and better completion of tasks. Therefore, in industrial production, besides improving work efficiency, we also need to consider the touch stability of industrial monitors. What are the differences between capacitive and resistive touchscreens in industrial monitors, and which is more suitable for industrial production?

A resistive touchscreen is a sensor that converts the physical position (X, Y) of a touch point within a rectangular area into voltages representing the X and Y coordinates. Many LCD modules use resistive touchscreens. These screens can use four, five, seven, or eight lines to generate the screen bias voltage and simultaneously read back the voltage of the touch point.

I. Advantages of using resistive touchscreens in industrial monitors:

1. High precision, down to the pixel level, applicable to a maximum resolution of 4096x4096.

2. The screen is unaffected by dust, moisture, and oil, and can be used in low or high temperature environments.

3. Resistive touchscreens use pressure sensing, allowing operation with any object, even while wearing gloves, and can be used for handwriting recognition.

4. Resistive touchscreens are relatively inexpensive due to mature technology and low entry barriers.

II. Disadvantages of using resistive touchscreens in industrial displays:

1. While resistive touchscreens can be designed for multi-touch, the pressure becomes unbalanced when two points are pressed simultaneously, leading to touch errors and making true multi-touch implementation difficult.

2. Resistive touchscreens are prone to yellowing.

3. Resistive touchscreens have lower light transmittance than capacitive touchscreens.

4. Resistive touchscreens are flexible and require some deformation. In environments prone to impacts, they are easily broken. Capacitive touchscreens, on the other hand, reportedly now have a surface material with very high strength that can withstand impacts without problems.

III. Capacitive Touchscreens: Capacitive touchscreens achieve multi-touch by adding mutual capacitance electrodes. Simply put, the screen is divided into sections, and each section has its own independent mutual capacitance module. Therefore, the capacitive touchscreen can independently detect touch activity in each section, process the data, and easily achieve multi-touch.

IV. Advantages of Using Capacitive Touchscreens in Industrial Displays:

1. Capacitive touchscreens only require touch, not pressure, to generate a signal.

2. Capacitive touchscreens require only one calibration after production, or none at all, while resistive technology requires regular calibration.

3. Capacitive touchscreens have a longer lifespan, as the components do not need to move. In resistive touchscreens, the upper ITO film needs to be thin enough to be flexible enough to bend downwards and contact the lower ITO film.

4. Capacitive technology is superior to resistive technology in terms of light loss and system power consumption.

5. The choice between capacitive and resistive technology mainly depends on the object touching the screen. For finger touch, capacitive touchscreens are a better choice. If a stylus is required, whether plastic or metal, a resistive touchscreen is suitable. Capacitive touchscreens can also use styluses, but require specialized styluses.

6. Surface capacitive touchscreens can be used in large-size touchscreens with relatively low cost, but currently do not support gesture recognition. Inductive capacitive touchscreens are mainly used in small to medium-sized touchscreens and support gesture recognition.

7. Capacitive technology is wear-resistant, has a long lifespan, and low maintenance costs for users, thus further reducing overall costs for manufacturers.

8. Capacitive touchscreens support multi-touch technology and are not as unresponsive or prone to wear as resistive touchscreens.

V. Disadvantages of using capacitive screens in industrial displays:

1. Workers in industrial control systems typically wear gloves, and frequently removing gloves to operate capacitive screens is inappropriate.

2. Capacitive screens are more susceptible to environmental factors such as temperature, humidity, and electromagnetic interference, which is unsuitable for the relatively harsh working environments of industrial control.

3. Currently, capacitive screens are relatively expensive, especially those supporting multi-touch, which are significantly more expensive.

As mentioned above, should industrial displays with touch functionality choose capacitive or resistive touchscreens? This depends on the actual usage environment. For example, capacitive touchscreens are generally chosen for bank ticket machines due to their relatively clean and comfortable environment with minimal interference. In large equipment manufacturing plants, where high temperatures or strong electromagnetic interference are common, resistive touchscreens are preferred.

Once a general direction is established for choosing an industrial display touchscreen, selecting the right industrial display manufacturer becomes crucial.

Answer 2

The main components of a mobile phone touchscreen include a sensor unit that processes user selections, a controller that senses and locates touch signals, and a software driver that transmits touch signals to the operating system.

These three types of components constitute the working mechanism of a touchscreen. Besides these components, touchscreens also come in several other technologies: capacitive touchscreens, resistive touchscreens, infrared touchscreens, surface acoustic wave (SAW) touchscreens, and near-field imaging (NFC) touchscreens.

Mobile phone touchscreens typically require testing. During testing, spring-loaded micro-needle modules can be used as connecting electronic components, serving to transmit current and offering stable and reliable performance. Capacitive touchscreens have a transparent conductive layer (ITO) coated on the surface, with voltage connected to the four corners. A small DC current is distributed across the screen surface, forming a uniform electric field. This makes operation more engaging, supports multi-touch, and prevents accidental touches.

This is because it only reacts when it senses the current from the human body. Resistive touchscreens consist of a display screen and a resistive film screen. The resistive film screen has two layers: a glass base layer coated with a transparent conductive layer, and an outer plastic layer also with a conductive layer.

When the screen is pressed or touched, the conductive layers come into contact, forming a contact signal and enabling operation.

Infrared touchscreens utilize light interruption technology. An outer frame surrounds the display, with a light source or LED on one side and a light detector or photoelectric sensor on the other, forming a crisscrossing infrared network.

When an object touches the display, the infrared light is blocked, allowing the touch point to be located on the screen. Acoustic touchscreens use sensors mounted on the edge of the glass screen to send ultrasonic signals.

The ultrasonic waves pass through the screen and are reflected, then received by the sensor. Surface acoustic wave (SAW) signals convert the surface acoustic wave energy from the reflected stripes into an electrical signal; guided acoustic wave technology converts the electrical signal sent from the controller through the screen cable into acoustic energy. Near-field imaging touchscreens consist of two thin glass layers. Applying an AC signal to the conductive layer generates an electric field on the screen surface. When a finger or stylus touches the sensor, the electric field is disturbed, and the screen receives a signal.

Answer 3

Based on sensor type, touchscreens are broadly categorized into five types: infrared, resistive, surface acoustic wave (SAW), capacitive, and electromagnetic.

Infrared touchscreens are inexpensive, but their frames are fragile, prone to light interference, and distort on curved surfaces. Capacitive touchscreens have a reasonable design, but image distortion is difficult to fundamentally resolve. Resistive touchscreens offer accurate positioning, but are expensive and easily scratched; these mainly include 4-, 5-, and 8-wire resistive touchscreens. SAW touchscreens overcome various shortcomings of previous touchscreens, are clear and durable, and suitable for various applications. However, water droplets and dust on the screen surface can cause the touchscreen to become unresponsive or even malfunction.

Infrared touchscreens have a circuit board frame mounted in front of the display. Infrared emitters and receivers are arranged around the four sides of the screen, forming a crisscrossing infrared matrix. When a user touches the screen, their finger blocks the horizontal and vertical infrared rays passing at that location, allowing the touchpoint to be determined. Any object can alter the infrared rays at the touch point, thus enabling touchscreen operation.

Infrared touchscreens are unaffected by current, voltage, and electrostatic interference, making them suitable for harsh environments. Their main advantages are low cost, easy installation, no need for cards or other controllers, and compatibility with computers of all levels. Furthermore, due to the absence of a capacitor charging and discharging process, their response speed is faster than capacitive touchscreens, but their resolution is lower.

Surface acoustic wave (SAW) touchscreens are mechanical waves that propagate along the surface of a medium. These touchscreens have ultrasonic transducers at their corners. They emit high-frequency sound waves across the screen surface; when a finger touches the screen, the sound waves at the touch point are blocked, thus determining the coordinate position. SAW touchscreens are unaffected by environmental factors such as temperature and humidity, offer high resolution, are scratch-resistant, have a long lifespan, and high light transmittance, maintaining clear and bright image quality, making them ideal for public places.

However, dust, water, and dirt can severely affect their performance, requiring frequent maintenance to keep the screen surface clean. Electromagnetic induction touchscreens work by relying on changes in the magnetic field generated by the electromagnetic pen and sensors beneath the panel. The electromagnetic pen acts as the signal transmitter, and the antenna board as the signal receiver. When the pen approaches the sensor, the magnetic flux changes, and the position is defined by calculation.

The electromagnetic touchscreen panel market is almost entirely dominated by the Japanese manufacturer Wacom. Electromagnetic touchscreen panels offer high light transmittance, high resolution, and high responsiveness, with Z-axis sensing capabilities, making them suitable for drawing, handwriting recognition, and other tasks. They also offer the advantage of allowing touch control without direct screen contact.

The precision and handwriting recognition capabilities of electromagnetic induction pens are ideal for drawing lines, annotations, and note-taking within text spaces, which is the main reason for their use in e-readers. Furthermore, electromagnetic touch modules are flexible and can be paired with software displays. The drawback is that they rely on the electromagnetic emission of the stylus for positioning, requiring the use of a pen for operation.

Therefore, e-readers using e-ink screens are all electromagnetic induction touchscreens and cannot be operated manually.

For resistive or capacitive touchscreens, the larger the size, the higher the unit cost. Electromagnetic touchscreens are the opposite; the larger the size, the lower the unit cost. In general, resistive or capacitive touchscreens are advantageous for sizes between 8 and 10 inches, while electromagnetic touchscreens are more price-competitive for sizes between 8 and 10 inches.