Capacitive touch technology is taking over the smartphone and tablet world, but it is risky for industrial use, where resistive panels still dominate thanks to rugged construction. David Jones explores a new, hardened resistive touch, which offers a viable alternative
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Author: David Jones BEng (electrical & electronic engineering), product manager, Yokogawa

Capacitive touch technology is taking over the smartphone and tablet world, but it is undeniably risky for industrial use, where resistive panels are still dominant – thanks to their rugged construction. However, a new, hardened resistive touch finally offers a viable alternative.

How many things have you touched so far today? It is not really a question we give much thought to and yet it lies at the heart of our basic daily actions. It starts from the second we wake up and lasts until the final moment of the day. From our alarm clocks, light switches, toothbrushes and door handles, to kettles, car keys and pens… you name it, we touch it. And the biggest culprit of all is our mobile phone.

This sneaky sidekick hankers for our attention constantly. Recent research published in the Journal of Behavioural Addictions (1) suggests that, on average, we check our mobile phone 150 times a day… that is, every six-and-a-half minutes.

It is a sign of a much larger shift in our consumer culture. It seems that the more technology has advanced, the more direct it has become. The trend in record amounts of technological investment has culminated in compelling devices offering larger screen sizes with highly accurate touch panels, all embedded under a polished and intuitive user interface.

The technology that underpins this revolution has had a staggered past. The early forays into touch-screen development used resistive-panel touch technology. Two flexible sheets of plastic covered in a metallic layer of electrodes would come into contact, horizontally and vertically when pressed, registering the precise location of the touch, made by a stylus, finger or pen.

Resistive technology did not catch on, however, because early iterations were not powerful enough to process multi-touch inputs, surfaces were not scratch proof and, due to the multi-layered plastics, visibility in sunlight was poor. Furthermore, poorly designed graphical user interfaces that were not optimised for touch, which meant that resistive screens fell well and truly into the technological chasm.

As the power of microprocessors has increased over the years, capacitive panel touch technology has come to replace resistive as the favoured norm in consumer electronics.

CAPACITATIVE CONTENDER

Resistive technology is offering an industrial alternative to capacitative touch technology

Many of us have undoubtedly experienced static shocks first hand. This is the human body exhibiting its extraordinary ability to store electrical charge when insulated.

This ‘body capacitance’ has been used to great effect by touch-panel engineers. In the early days, surface capacitance was used by coating a piece of glass on one side with a transparent conductive material such as indium tin oxide (ITO). A voltage was applied at the four corners of the panel, creating a uniform electrostatic field.

As a finger came into contact with the surface, the potential difference in the capacitance would alter the amount of current drawn at each corner, allowing the microcontroller to calculate the exact input position.

Surface capacitance worked well for simple applications such as retail kiosks. However, due to costly calibration during manufacture, the inability to multi-touch and the tendency to register false detection, these were replaced by the more modern projected capacitance, which is used widely in today’s smartphones and tablets.

The wars of the millimetres have seen manufacturers race to produce ever-thinner devices. Projected capacitance moves the sensor from the glass surface to the printed circuit board. Electrodes aligned in a row and column pattern detect any changes in the electrostatic field. By constantly measuring sudden changes in capacitance, modern devices can offer multi-touch input and gestures.

INDUSTRIAL USES

David Jones

There is no doubt that touch screens are more effective; they reduce the cost of training because hand gestures like pinch to zoom, swiping and multi-touch are all more intuitive than using physical buttons to navigate complex tiered menu systems.

Whilst arguably adequate for everyday consumer use, capacitive glass touch-screen technology is unsuited for more demanding industrial environments, where the risk of the glass breaking makes it dangerous to use. An operative in the pharmaceutical or chemical industry will wear gloves for hand protection, preventing capacitive touch. As a result, older resistive displays have always been used.

To combat this problem, Yokogawa has developed the Smartdac+ GX and GP series of paperless recorders, which boast the benefits of a capacitive screen, whilst eliminating the shortcomings of resistive technology.

Rated to NEMA4 and IP65 standards, the entire front panel assembly uses a hard coated display surface, which is splash resistant and wash-down resistant against numerous acids including hydrochloric acid, sodium hydroxide and ethanol. This enables the use of a stylus for handwriting input whilst wearing gloves, without scratching or corroding the panel.

The hard coating also increases the contrast ratio of the panel, giving greater clarity and visibility with wider viewing angles in harsh lighting conditions. Driven by intuition, we have developed completely new firmware that offers multi-touch gestures such as pinch-to-zoom, swipe and click-and-drag. This is all powered by a specially designed microcontroller circuit board.

The recorders further improve on previous iterations by minimising hardware buttons to a single home button and adding 100 channels of plug-and-play modular input/output support. Data security is maintained with multiple backups and increased connectivity; even the web remote view sessions are encrypted.

It is evident that touching is embedded within our very nature. As graphical and processing technologies continue to develop, we will see the increased ubiquity of touch in our work and personal lives. So perhaps you might spare a thought for the developer, the next time you reach for your mobile phone.

See www: www.yokogawa.com for more information.

Reference:

1) James Roberts, PhD, professor, marketing department, Hankamer School of Business Baylor University, Waco, Texas; James Maddux, PhD, professor emeritus, department of psychology, George Mason University, Fairfax, Va.; Nov. 17, 2012, Journal of Behavioral Addictions, online

http://www.engineersjournal.ie/wp-content/uploads/2014/04/Touch-screen-1024x769.jpghttp://www.engineersjournal.ie/wp-content/uploads/2014/04/Touch-screen-300x300.jpgDavid O'RiordanTechpharma
  Author: David Jones BEng (electrical & electronic engineering), product manager, Yokogawa Capacitive touch technology is taking over the smartphone and tablet world, but it is undeniably risky for industrial use, where resistive panels are still dominant – thanks to their rugged construction. However, a new, hardened resistive touch finally offers...