Touch screens 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 touch screens? The five most common types of touch screens 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 touch screen 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

Surface Capacitive

Surface capacitive is the second most popular type of touch screen on the market. In a surface capacitive touch screen, 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 touch screens can only be activated by the touch of human skin or a stylus holding an electrical charge.

ADVANTAGES:

  • Better image clarity than resistive touch screens
  • 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)

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 touch screens
  • 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

Surface Acoustic Wave (SAW)

SAW touch screen 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 touch screens
  • 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

Infrared Touch (IR)

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.

ADVANTAGES:

  • Highest image clarity and light transmission of all touch screen 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

Touch Screen For Industrial Environments

All touch screen 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 touch screen interfaces. The most advantageous touch screen interface type for industrial and automation environments tends to be resistive touch screens. Since resistive touch screens 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 top of a glass substrate. Resistive touch screens prevent any exposed glass and allow use in these type of applications. Many types of touch screen interfaces can excel in many environments, so it’s best to research what the application environment will consist of, before choosing the type of touch screen interface that would be ideal for your operations.  

TOUCH SCREEN 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

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