Simon WyreFor several years now, many of the gadgets we use around the house, on the move and in the workplace have contained some form of visual display to impart status information to the user and even allow the user to interact with them via a touch screen. In the early days, you might have found a vacuum fluorescent or LED display on the car stereo or home music system to be followed later by the LCD. Nowadays, displays on appliances are commonplace.

There are many factors that have led to their uptake:

• There is more going on in the product, which needs communicating to the user
• The product is more likely to have a processor
• It can be used to add value or enhance the product’s selling power
• Reduced cost of components
• Better display driver circuits
• Faster, cheaper processors – especially flash-programmable microcontrollers
• Greater user expectation – driven in part by the pervasion of PCs and mobile phones

A parallel trend has developed in industrial applications where metering has been an essential part of most factory processes. As the control of those processes gets ever more sophisticated, so does the information the instrument has to impart but there is only so much a 7-segment display can show.

Luckily, people are much more comfortable with technology. The PC in the workplace or at home is the norm, not the exception. PC suppliers – both software and hardware – have striven to make their products easy and intuitive to use. Graphical user interfaces combined with Plug and Play accessories and now USB peripherals, self-configure and if any software is needed, it is usually a simple matter of inserting a CD and waiting for it to install the necessary applications. This poses some opportunities and real challenges for the designer, especially where low volume runs apply or where the skills needed to design an HMI are lacking. Then there is the inevitable issue of time to market.

To date, the answer has usually been to employ embedded panel-mounted PCs, complete with operating systems like Windows CE or Linux. They do, however, have several disadvantages.

• High cost in hardware and sometimes software
• High power consumption
• Physically large
• Still require some PC skills to setup

Despite developments in PC and electronics technology, the embedded PC is often an overkill when it comes to many panel and instrumentation applications. The huge drop in the cost of color touch screens, driven by the global market in mobile phones, coupled with the introduction of low-cost high-speed 16-bit microcontrollers, has enabled developers to introduce products with much smaller footprints and which don’t need an operating system. Apart from the security and reliability advantages that brings, it allows plug and play to be brought down to the component level.

The instrument can display its data in any form –analog, digital or even a mimic display and unlike the old 7-segment LED or LCD, the graphical meter is better suited to showing alarm or error states. Color capability further enhances this. Touch screens allow the designer to put buttons anywhere. These sorts of advantages are exploited by the Lascar PanelPilot system, for example, which uses the mobile phone ‘app’ concept to give users the means to create any number of meter solutions, simply by downloading the application which suits their requirements form the PanelPilot web site Configuration is done by simple point and click PC software. As new applications come along, the user can change as necessary. Obsolescence is limited and there is less waste as components can be upgraded or even re-deployed. 

Lascar's PanelPilot: The user can chose from a range of meter sizes and applications such as voltmeters, thermometers, trend indicators etc.

For distributors, this brings benefits, because they need only stock a limited range of units.

As component prices continue to fall, the soft display will inevitably gain ground over older display technologies. The adaptability of soft displays means that there is less risk for the designer, who can alter the meter’s appearance or even functionality without even removing it from the panel. If they really want to, the soft meter can even mimic a 7-segment display.