Adapting touch for harsh environments
01 December 2017
Designers of industrial equipment and Human Machine Interfaces (HMI’s) have embraced touch technology, using it alongside as well as replacing traditional mechanical dials, buttons and levers to provide reliable interaction and control on complex machines and systems.
Implementing touchscreen technology in demanding environments is very challenging and many different factors need to be considered, including exposure to extremes of hot and cold temperatures, chemicals, salt water, oil and more depending on the location and conditions.
Users of HMI’s also need to be confident in the equipment they are using and that it will provide ultimate reliability and respond as required, even when wearing protective gloves.
The proprietary PCT Projected Capacitive Technology (p-cap) developed by Zytronic has on many occasions proved its ability to be employed in the most uncompromising of environments - including the extreme conditions encountered in oil and mining industries. Its touchscreens offer a robust, waterproof, and hygienic solution that will detect a finger, conductive stylus and even a gloved hand, through glass thickness of 20mm or more. Recent successes in heavy industry have further underlined this, including applications in the middle of the ocean, and deep underground.
Touch in an explosive environment
Mission critical control specialist Smart-Ex selected durable ZYTOUCH sensors for its rugged, ATEX rated, control panels used on offshore oil and gas rigs, to enable the collection and analysis of data by engineers. Operators depend upon an interface that is easy to use, so information can be rapidly viewed, understood and acted upon. It was essential that the touchscreens were capable of faultless outdoor 24/7 operation, exposure to corrosive salt water, and oil, while remaining responsive to the touches of users often wearing heavy work gloves.
Customised 15 and 19in versions of the highly rugged PCT touch sensors have been integrated into the Smart-EX terminals, along with ZXY100 high performance touch controllers, and they are already being deployed on oil rigs worldwide. Using thermally toughened, laminated glass in thicknesses of up to 23mm, the touch interactive, completely sealed and intrinsically safe terminals are capable of coping with the rigours of Zone 1 hazardous environments.
Australian mining application
Australian kiosk manufacturer FM Scanu is another company that has endorsed the highly durable Project Capacitive Technology (PCT), selecting the touchscreen technology for use within systems deployed at mining giant BHP Billiton. The resulting ruggedised kiosks were designed to assist the management of mine personnel, making use of the high performance of the touch technology by incorporating a 17? ZYPOS touch sensor. The kiosks provide occupational health and safety information to miners in a hectic excavation environment and Zytronic’s p-cap technology ensures that the touchscreens operate dependably year-round.
The ZYPOS sensor consistently delivers reliable performance, which is crucial in such a harsh environment, where coal dust, grit and moisture are prevalent. The kiosk’s operation was also unaffected when used with a gloved or dirty hand, so that information could be accessed without the hindrance.
Zytronic’s PCT touch sensing method of embedding microfine copper electrodes in a durable laminated substrate, provides leading signal-to-noise ratio touch detection. In this application, it allows the tough, all glass p-cap sensor to be mounted behind (and operate through) an additional thick protective overlay of glass, which can be inexpensively replaced if damaged.
As another significant benefit, especially useful in remote mining locations where the cost of servicing can be high, is the fact that PCT is not prone to drift over time, and can be completely sealed into IP67 enclosures. This makes it ideal for demanding industrial, outdoor and unattended touch applications where high levels of reliability and “up-time” are mission critical.
Zytronic’s PCT and multi-touch detecting MPCT p-cap sensors are both capable of detecting touches through very thick glass and protective overlays, even with heavily gloved hands. This is because they offer high levels of Z-axis sensitivity and control which can be tuned to suit the application by the system integrator. Coupled with Zytronic designed touch controllers, they offer a reliable and intuitive touch experience, responding accurately to up to 40 touches.
Although for smaller displays, users generally only touch the screen with one or two fingers at a time, full multi-touch functionality brings advantages particularly for larger screens (e.g. over 30in). For example, “palm rejection”, where a touch sensor and controller ignores a hand resting on the screen but still recognises and responds to an intentional touch, requires multi-touch support to function correctly.
Improved immunity to EMI
Electro-magnetic interference (EMI) is often an issue for p-cap touchscreen systems placed into industrial environments. Similarly, touchscreens deployed in areas where the power supply is inconsistent or not well regulated may also be affected by transient interference coming up the power cable from the mains supply. This can create problems for touch sensors and their control electronics in terms of identifying the signal (or touch) from the surrounding interference (“noise”), i.e. decreasing the signal-to-noise ratio, and thereby impairing the identification of true touch events.
Major improvements to the electronic design and touch detection firmware employed by the touch controller are ensuring that signal integrity is maintained at a high level. All p-cap touch technologies rely upon an X-Y matrix of conductive electrodes which can be made from a variety of materials. These are typically embedded within a laminated glass substrate and when connected to suitable touch control electronics, they can detect small changes in the applied capacitance within the conductive matrix resulting from the proximity of a grounded conductive object, such as a finger or stylus. One method to combat EMI is to implement a ‘smart’ frequency-scanning function in the touch controller. The operating frequency moves dynamically to avoid detected environmental, ambient ‘noise’ that would otherwise prevent the detection of touch events. This methodology has been used in Zytronic’s patented ZXY110 controller range, which scans between 1.3 and 2.5MHz to find the frequency with least interference, without interrupting the touch function.
With advanced features including multi-touch and immunity to EMI, using a p-cap touchscreen alongside or instead of mechanical controls can offer huge advantages for the system designer. With multi-function interfaces, users need only be offered the relevant options available at the correct point in a process or operation, reducing the risk of error and making the instrument more intuitive to use. By selecting the correct p-cap technology, the interface can also readily be protected against mechanical damage and the environment, and provides flexibility beyond the reach of other technologies.
The two applications described in this article demonstrate that there is almost no environment that is too difficult for the right touch technology to provide a constantly reliable and responsive solution. Zytronic PCT and MPCT sensors can be manufactured in a near limitless range of shapes and sizes from very thick, thermally toughened glass and be sealed into a suitably rugged enclosure, responding to operators who are themselves wearing protective workwear such as gloves. As a result, such high-performance touch interfaces are sure to become as widespread in the industrial workplace as they are in the hands of consumers.
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