Touch screens have become very commonplace in our day-to-day lives. Devices using touch panels to enable user interaction without the use of keyboard or mouse. But do you know there are couple distinctively different types of touch screens? The five most common types are: Resistive, Surface Capacitive, Projected Capacitive, Surface Acoustic Wave and Infrared.
Resistive Touch is the most widely used touch technology these days. Because it is cheaper to make and easier to use in different environments. A resistive touch screen is composed of two very thin layers of material, separated by a thin gap. The top layer is typically some type of clear polycarbonate material, while as the bottom layer is made from rigid material. LCD manufacturers normally use PET film and glass for these layers. The upper and bottom layers are lined with conducting material like indium tin oxide (ITO), facing each other, separated by a narrow gap. When a user touches the screen, two metallic layers make contact, it creates a change in resistance.
There are 3 types of resistive touchscreens. The type of resistive layout determines the durability and sensitivity of the entire circuit.
In a 4-wire analog setup, both the top and bottom layers contain two electrodes called “bushbar”. These electrodes are oriented perpendicular to one another.
Electrodes on the top are positive and negative Y axis, while the ones on the bottom are positive and negative X axis. Using this setup, screen can sense the coordinates where the two layers have come in contact.
A 5-wire analog setup consists of four electrodes placed at each corner of the bottom layer; four wires then connect these electrodes together. The fifth wire is the “sensing wire” embedded in the top layer.
When user’s finger or stylus makes an area of the two layers touch, the sensing wire sends the voltage for the coordinates to device processor. With fewer components and a simpler design, the 5-wire analog circuit is a bit more durable than other designs.
The most sensitive resistive touch screen design is that of the 8-wire sensing circuit. Its layout is similar to the 4-wire one, but each of the “bushbar” connects with two wires.
8-wire touchscreens can easily detect the precise location of touch commands, and are more stable than 4 & 5-wire solutions.
- Can be activated with virtually any object (finger, stylus, gloved hand, pen, etc.)
- Has tactile feeling
- Lowest cost touch technology
- Low power consumption
- Resistant to surface contaminants and liquids
- Lower image clarity compared to other touch technologies
- Screen material is usually more prone to scratch and damage
- Less sensitive to light touch
Capacitive touch panel technology relies on the capacitance of the human body, and not on mechanical pressure like resistive technology. There are two types of capacitive touch panels – surface capacitive and projected one.
Surface Capacitive Touch are the second most popular type of touch screens on the market. In a surface capacitive touch panel a thin glass surface covers capacitive touch screen. Under this glass surface, lies a thin layer of transparent electrodes on top of LCD glass panel.
When a human finger touches the screen, some of the electrical charge transfers from the screen to the user. The change in capacitance is detected by sensors located at the four corners, allowing controller determine the touch point.
Projected Capacitive is like Surface Capacitive, with two main advantages: besides bare finger, it can also be activated with fingers inside thin surgical or cotton gloves; and it enables multi-touch activation.
Beneath the glass with protective cover, there is a pattern of electrode layers – or the matrix. This pattern forms the plane of X and Y coordinates which the controller uses to calculate the event of touch.
- Better image clarity
- Durable screen, high scratch resistance
- Resistant to surface contaminants and liquids
- Sensitive to EMI/RFI
- Requires bare finger or capacitive stylus
Surface Acoustic Wave Touch
SAW (Surface Acoustic Wave) touch screen utilizes a series of piezoelectric transducers and receivers along the sides of the glass plate to create an invisible grid of ultrasonic waves on the surface. When the panel is touched, a portion of the wave is absorbed. This allows the receiving transducer to locate the touch point and send this data to the computer. SAW monitors can be activated by a finger, gloved hand, or soft-tip stylus. SAW monitors offer easy use and high visibility.
- Excellent image clarity
- Better scratch resistance than capacitive screen
- High “touch life”
- Will not work with hard items
- Water droplets may cause false activation
- Solid contaminants on the screen can create no-touch areas
Infrared touch screen monitors do not overlay the display with an additional screen or screen sandwich. Instead, infrared monitors use IR emitters and receivers to create an invisible grid of light beams across the screen. This ensures the best possible image quality. When an object interrupts the invisible infrared light beam, the sensors are able to locate the touch point.
- Highest image clarity and light transmission of all touch technologies
- No “touch-life” issue
- Invulnerable to surface scratches
- Accidental activation may occur since infrared beams are above glass surface
- Foreign object buildup on screen or frame could impede infrared light beam
- Sensitive to water, snow and rain
- May be sensitive to ambient light interference
- Higher cost
Topway LCD modules come with both Resistive Touch and Capcitive Touch. You can browse our product for more information.