Top 5 Touchscreen Interfaces

What are the most common types of touchscreen interfaces?

Touchscreens have a very commonplace in our daily lives: cell phones, ATM’s, kiosks, ticket vending machines, and more. They all use touch panels to enable the user to interact with a computer or device, without the use of a keyboard or mouse. But did you know there are several different types of touchscreens? The five most common types of touchscreens are 5-wire resistive, surface capacitive, projected capacitive, surface acoustic wave (SAW), and infrared.

5- Wire Resistive

5-wire resistive is the most commonly used touch technology today. A resistive touchscreen is composed of a glass panel and film screen, each covered with a thin metallic layer that’s separated by a narrow spacing. When a user touches the screen, the two metallic layers make contact, resulting in an electric flow. The point of contact is detected by this change in voltage.

ADVANTAGES:

• Can be activated with virtually any object – finger, stylus, gloved hand, pen, etc.
• Has tactile feel
• Lowest-cost touch technology
• Low power consumption
• Resistant to dust, oil, grease, moisture, and other liquids

DISADVANTAGES:

• Lower image definition compared to other touch technologies
• Outer polyester film is vulnerable to damage from scratching, poking, and sharp objects

4- Surface Capacitive

Surface capacitive is the second most popular type of touchscreen on the market. In a surface capacitive touchscreen, a transparent electrode layer is placed on top of a glass panel and covered by a protective cover. When an exposed finger touches the screen, it reacts to the static electrical capacity of the human body. Some of the electrical charges transfer from the screen to the user. This decrease in capacitance within the screen is detected by sensors located at the four corners of the screen, allowing the controller to determine the touch point. Capacitive touchscreens can only be activated by the touch of human skin or a stylus holding an electrical charge.

ADVANTAGES:

• Better image clarity than resistive touchscreens
• Durable screen
• Excellent resistance to surface contaminants and liquids- dust, oil, grease, water droplets
• High scratch resistance

DISADVANTAGES:

• Requires bare finger or capacitive stylus for activation
• Sensitivity to Electro-Magnetic Interference (EMI)/Radio Frequency Interference (RFI)

3- Projected Capacitive

Projected capacitive is similar to surface capacitive, but offers two primary advantages. In addition to a bare finger, it can also be activated with surgical gloves or thin cotton gloves. It also enables multi-touch activation (simultaneous input from two fingers). A projected capacitive is composed of a sheet of glass with embedded transparent electrode films and an integrated chip (IC), which creates a three-dimensional electrostatic field. When a finger comes into contact with the screen, the ratios of the electrical currents change, and the computer is able to detect the touch points.

ADVANTAGES:

• Excellent image clarity
• More resistant to scratching than surface capacitive touchscreens
• Resistant to surface contaminants and liquids- dust, oil, grease, moisture
• Multi-touch (two-touch)

DISADVANTAGES:

• Sensitive to EMI/RFI
• Must be activated via exposed finger, thin surgical or cotton gloves

2- Surface Acoustic Wave (SAW)

SAW touchscreen monitors utilize a series of piezoelectric transducers and receivers along the sides of the monitor’s 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 the data to the computer. SAW monitors can be activated by a finger, gloved hand, or soft-tip stylus. SAW monitors offer easy to use and high visibility.

ADVANTAGES:

• Excellent image clarity
• Even better scratch resistance than capacitive touchscreens
• High “touch life”

DISADVANTAGES:

• Will not activate with hard items- pen, credit cards, or fingernails
• Water droplets may cause false triggering
• Solid contaminants on the screen can create non-touch areas until removed

1- Infrared Touch (IR)

Infrared touchscreen 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.

ADVANTAGES:

• Highest image clarity and light transmission of all touchscreen technologies
• Unlimited “touch-life”
• Impervious to surface scratches

DISADVANTAGES:

• Accidental activation may occur because infrared beams are actually above the glass surface
• Dust, oil, or grease buildup on screen or frame could impede light beam causing malfunction
• Sensitive to water, snow, and rain
• May be sensitive to ambient light interference
• Higher cost

Touchscreen For Industrial Environments

All touchscreen interfaces have advantages and disadvantages, depending on their application. For industrial use, there typically are requirements and nuances that lend better to certain types of touchscreen interfaces. The most advantageous touchscreen interface type for industrial and automation environments tends to be resistive touchscreens. Since resistive touchscreens allow the use of gloves and stylus, the user will not be bothered with having to remove gloves or protective wear in order to use the device. Some industry facilities, like food and beverage, require a strict “no exposed glass” policy. Resistive touch interfaces employ a flexible- polycarbonate in most cases- sheet over the top of a glass substrate. Resistive touchscreens prevent any exposed glass and allow use in these types of applications. Many types of touchscreen interfaces can excel in many environments, so it’s best to research what the application environment will consist of before choosing the type of touchscreen interface that would be ideal for your operations.

TOUCHSCREEN COMPARISON
	5-WIRE RESISTIVE	SURFACE CAPACITIVE	PROJECTED CAPACITIVE	SAW	INFRARED
CLARITY	XX	XXX	XXX	XX	XXXXX
SENSOR SUBSTRATE (TOP COATING)	Polyester top sheet. Glass substrate with ITO coating	Glass with ITO coating	Glass with ITO coating	Glass with ITO coating	Any substrate
EASE OF TOUCH ACTIVATION	XXXXX	X	XX	XXX	XXXX
TOUCH SENSITIVITY	XX	XXX	XXX	XXXX	XXXXX
CALIBRATION STABILITY	XXX	XX	XXX	XXXXX	XXXX
ACCURACY AND REPEATABILITY	XXX	XX	XXXXX	XXXX	XXX
SCRATCH RESISTANCE	X	XXX	XXXXX	XXXXX	XXXXX
HUMIDITY SENSITIVITY	XXXXX	XXXXX	XXXXX	XXX	XXXX
SENSITIVITY TO RAIN/SNOW	XXXXX	XX	XXXX	XX	XXXXX
SENSITIVITY TO CLEANING CHEMICALS	XXX	XXXX	XXXXX	XXX	XXXXX
SENSITIVITY TO SURFACE CONTAMINANTS	XXXXX	XX	XXXX	XX	XX
EMI/RFI SENSITIVITY	XXXXX	XX	XX	XXX	XXXXX
VIBRATION SENSITIVITY	XXXXX	XXX	XXXX	XXX	XXXX
SENSITIVITY TO AMBIENT LIGHT	XXXXX	XXXXX	XXXXX	XXXXX	XX