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Selecting a touchscreen

09 January 2017

Touchscreens are found on consumer devices but are now increasingly being used in industrial environments. However, there are different types of touchscreens which users must consider. Noel Sheppard, director of industrial computing specialist Distec is your guide

Touchscreen technology has come a long way since it was first used in 1966 in a radar screen used by the Royal Radar Establishment (RRE) for air traffic control. Despite it being bulky, slow, imprecise and very expensive, it was in use until the 1990s. Since then, consumers have come to expect quick and responsive touchscreens, which are increasingly used in industrial environments.

Resistive screens

Resistive touchscreens are typically found in retail electronic point of sale (EPOS) devices and companies have traditionally used them in industry. These have several layers, including two thin transparent, electrically resistive layers, separated by a thin space. When an object such as a fingertip or stylus tip presses down on the outer surface, the two layers touch to become connected. These touchscreens simply need enough pressure for the touch to be sensed and can be used while wearing gloves or other personal protective equipment (PPE).

Resistive technology has historically been much cheaper than the newer projected capacitance (PCAP) technologies. The higher resistance to liquids and contaminants is also particularly beneficial in restaurants, factories and hospitals, where there is a risk of spillages. Resistive touchscreens can also be protected by the use of a cover sheet. This is particularly important in the food industry where, in the case of breakage, glass shards do not contaminate food. A cover sheet contains the spread of any shards to prevent them from shattering over the production area.

A drawback of resistive screens is that they tend to be more opaque and the clarity of the screen is lower. For some industrial environments, this is not an issue and the robustness and low costs makes resistive touchscreen technology a reliable choice.

Capacitive screens

Recent developments in touchscreen technology have led to the widespread use of capacitive touchscreens. Anyone that uses a modern smartphone or tablet will be familiar with capacitive technology.

A variant of this technology, projected capacitance (PCAP) touchscreens, function in a different manner to resistive touchscreens. They are formed of rows and columns of conductive material, which is layered on sheets of glass. When voltage is applied to the grid, it creates a uniform electrostatic field. This field is disrupted when a conductive object such as a finger comes into contact with the grid. This exact point of contact is then measurable due to a change in capacitance, meaning the computer can accurately track touch input.

PCAP touchscreens are being increasingly used in retail environments. These use multi -touch technology, which allows for a simple-to-use interface that requires no training. Additionally, they can have anti-glare covers and cover the device from edge to edge, meaning there are no bezels, improving the aesthetic appeal of the device.

Application

To protect the touchscreen and the PC itself against vandalism or damage, PCAP touchscreens feature a layer on the outer surface otherwise known as a sacrificial layer. Although traditionally made from glass and prone to etching and damage, these layers can now be made from polymers, which remove the potential of damage to the layer, yet also eradicate the potential of shattered glass.

Key Points

  • Resistive touchscreens simply need enough pressure for the touch to be sensed and can be used while wearing gloves or other PPE
  • PCAP touchscreens use multi -touch technology, which allows for a simple-to-use interface that requires no training
  • To protect the touchscreen and PC against vandalism or damage, PCAP touchscreens feature a sacrificial layer on the outer surface

 
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