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Touch technologies at a glance

Operation of a machine via the touchscreen  

Perfectly suited to industrial applications

The touchscreen is a popular control element that invokes a reaction from the system to be operated by touching a special surface. The touch-sensitive surface is the touch sensor. Combined with a touch controller and a software driver, these components make up the touchscreen. In addition to the functionality and flexibility, the touchscreen has been developed to be used predominantly in industrial applications thanks to its low space requirements.

The analog-resistive polyester touch and the projective-capacitive touch (P-CAP) are used together in more than 80 percent of all industrial applications. As such, selecting the right touchscreen primarily depends on two criteria:

  • Operating conditions: inside or outside come rain or shine, mechanical load, chemical load, temperature, humidity, dust, EMC, etc.
  • Operating mode: fingers, gloves or other tools

Method of operation

Finger touches the touchscreen  

Touch operation

As opposed to using a classic input device, such as a mouse or a keyboard, when it comes to a touchscreen, other tools are also used in addition to fingers, such as a stylus. Depending on the technology used, the following environmental conditions are recorded and used to determine the position:

  • Haptic signals (pressure)
  • Electrostatic signals (charge)
  • Acoustic signals (ultrasound)
  • Visual signals (infrared rays)
  • Electromagnetic signals (voltage)

 

The signal is processed by the touch controller after it has been registered by the touch sensor. Finally, the touch controller transmits the information regarding the location of contact to the user interface. In order for this information to be processed and interpreted, the software driver must be installed beforehand.

The software driver itself corresponds to a mouse emulator. In other words, touching the touch-sensitive surface is perceived as a mouse click in the same position. Similarly to a mouse click, briefly touching the touchscreen sets off a corresponding reaction. The same applies to two brief touches in a short space of time (double-click) or other functions such as drag and drop.

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Touch technologies

Due to the diverse requirements and operating conditions there are a range of different versions. These are essentially based on the following technologies:

Analog-resistive systems to acquire haptic signals (pressure)

  • Polyester touch with 4-wire, 5-wire or 8-wire design
  • Multi-finger operation based on the 5-wire design
  • Glass-film-glass touch (GFG touch)

Capacitive systems to acquire electrostatic signals (charge)

  • Surface-capacitive touch
  • Projective-capacitive touch

Both touch technologies feature properties that have downsides in certain operating conditions. For such special cases, other touch technologies exist that have only been applied to a few applications to date:

  • SAW = acoustic systems that use ultrasound to determine positions
  • IR touch = visual systems that use infrared beams to determine positions

Use the selection guide to compare the various technologies and find the right system for your application.

Description Language
Selection guide [PDF, 28 KB]
Touch technologies
English
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Polyester touch

Polyester touch structure  

Structure of a polyester touchscreen

A resistive touchscreen consists of two polyester plates that lie on top of each other, which are coated with the semiconductor indium tin oxide or ITO. Spacers are used to create a gap between the plates that is filled with air. As soon as pressure is placed on the top plate, this is pressed downward and the two semiconductor coatings make contact. The contact is triggered with a finger or any other object.

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Projective-capacitive touch (P-CAP)

Projective-capacitive touch structure  

P-CAP touchscreen structure

A transparent ITO layer underneath the glass cover, consisting of touch sensors, projects a uniform electrical field that extends through the glass to the user. The electrical field changes in the event of touch contact. Thicker glass and operation when wearing gloves are no problem. The touch controller localizes the coordinates with high precision.

In terms of the design of the cover glass, there are no limits for engineers. Hardened glass is also very robust and durable when it comes to aggressive substances. A multitouch function is also essentially viable; this however depends on the operating system used.

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Glass-film-glass touch (GFG)

Glass-film-glass touch structure  

GFG touchscreen structure

The GFG touch combines the proven, pressure-based analog resistive touch technology with a high-quality glass design. The surface here is not polyester film but rather a thin, resistant glass sheet. The glass layer serves to prevent moisture penetrating the system. As such, the GFG touch is particularly suited to harsh ambient conditions.

The device can be operated with fingers, gloves, stylus or any other object, without causing damage.

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Further information

PHOENIX CONTACT (Ireland) Ltd

C6 The Exchange
Calmount Park
Ballymount
Dublin 12
D12 XE18
Ireland
(01)2051-300