From industrial panel PCs, to open-platform graphic operator interface terminals (OITs), to microOITs, to human-machine interfaces (HMIs), there are many choices of interactive display technologies for manufacturing and process control. It can be a challenge to decipher the right product for the right application — even for the more technically minded individual, let alone the business owner who simply wants his process automated. The best way to get a handle on these products is to categorize them and then describe each group.
Alpha Numeric OITs
Let’s start with the most basic display interface terminal — the alphanumeric OIT. Often called microOITs, these operator interfaces have been around for years and are simply a combination of a monochrome display (with room for 40 to 80 characters) combined with a programmable key-pad containing function keys (usually 12 to 24 of them). The display on these units simply provides the visual feedback for the function performed.
MicroOITs are prevalent everywhere, from the temperature thermostat in your house, to the programmable key-code entry lock on your garage door, to the keypad entries on a gas pump. The higher quality units come with rugged metal enclosures, as well as a wide range of controller drivers. And those with a Class I Division II rating will perform well even in extreme ranges of temperature (one popular brand will function in temps ranging from -10 to 65 oC).
The display on a microOIT consists of either a backlit LCD (Liquid Crystal Display) or a VFD (Vacuum Fluorescent Display). Choose the VFD microOIT when you need a light-emitting display for low-light environments and those situations where crisp, high-contrast readability is in order. Be mindful, though, that VFD displays are not well suited for extremely bright conditions (especially sunlight).
Conversely, the liquid crystal display is more appropriate for normal lighting conditions, but with a backlight they can still be viewed in the dark — just not to the degree of the VFD. Just be mindful that your choice should hinge upon the prevalent lighting condition.
HMI or Graphic OITs
Today, when most people think of an HMI they think of a touchscreen control panel — a display that utilizes proprietary configuration software that allows you to create an interactive touchscreen application that can communicate with a controller, another HMI, or an industrial computer/panel PC. The configuration process involves loading the software onto a PC and then creating your application. Then the application is generally downloaded via serial, USB, or Ethernet cable to your HMI.
HMIs range in size from tiny 3" screens all the way to 15" (and larger), and they can be utilized as a data collection terminal, a data display terminal, a touchscreen control panel for OEM applications, and as a plant floor industrial terminal. HMIs are used either singularly or networked in all locations of the control /automation process.
Recently, HMIs have undergone some impressive technological advances like high-resolution widescreen displays with hundreds of thousands of pixels; the ability to display up to 65,000 bright, crisp colors; the ability to create HMI applications in either landscape or portrait mode (you can orient your HMI with the short side up); and the ability to play gif animations and even play video (on the faster models).
With these new advances, you can create applications on your touchscreen display that will have the visual cues that relate directly to the operation. And standard technical functionality includes things like data entry, data logging, data sampling, process monitoring, recipes, bar graphs, meters, trends, alarms, switches, etc. that all allow you to engage and control your process.
It is important to remember that the limitation of the HMI/graphic OIT is that it only runs the proprietary configurations software. Unlike a PC, it will not run other software like Windows®-based applications.
Open Operating Platform HMIs
If you want more software options or simply need more in your HMI than the proprietary configuration software can deliver, then an open HMI might be a logical choice to meet that need. The open HMI has a touchscreen display like the standard HMI control panel, but it has an open-platform operating system like Windows CE or Windows XP that allows you the ability to utilize other Windows-based applications.
So let’s say you want to utilize a more substantial configuration software. The Windows operating system will allow you to do that. And of course, with the Windows operating system, you have access to a whole new universe of software applications and features like Web browsing. And with the browsing capability, you can network your open HMI over the Internet, take advantage of files in the HTML format, and of course, take advantage of any other online capabilities.
Your choice of CE or XP-embedded will depend upon two factors. The first is simply the fact that Windows CE is a much shaved-down version of XP and is therefore less expansive. But it also requires much less hardware capacity (memory, processor) to operate correctly. The XP version gives you the expanded options of the full operating system, but it is more expensive and it does require more substantial hardware.
It is important to remember, though, that in either case, the open HMI is not a full-fledged PC or industrial computer. It’s an HMI with an expanded capability. Think of it as the midway point between an HMI and full-fledged industrial computer or panel PC.
Panel PCs or Industrial Touchscreen Computers
Panel PCs are an interactive touch-screen display technology that offer the efficiency, power, and connectivity to create an automation process based upon your primary design objectives, rather than being forced to sidestep around the limitations and design roadblocks imposed by conventional HMIs/panel PCs.
Panel PCs are full-fledged industrial computers with touchscreen displays, fast processors, lots of memory and drive space, the Windows XP Pro Operating System, and beefed up connectivity with several USB and Ethernet and serial ports — all encased within a durable enclosure that panel-mounts into a console or instrument panel. They come in both light industrial and heavy industrial product lines; the heavy industrial with a more rugged design, anti-shock drives, and much more substantial enclosures.
Panel PCs have all the capabilities of any full-strength PC and can literally be placed at any level of your automation control process. From the corporate home office to the plant floor of your manufacturing site, the panel PC gives you all the power and options you’ll need.
And like any HMI, they can be networked over and into the entire automation process to communicate with other panel PCS, other HMIs, or even the corporate server. You can treat it like a standard PC with a keyboard, or utilize its touchscreen capability. Yet, like all HMIs, there’s no tower — all hardware is packed tightly behind the display.
These units offer much greater latitude in the creation and facilitation of the automation and control process. Although substantially more expensive, they should not be overlooked for their capability provides you with many options not otherwise available.
Control Operator Interface Terminals
This technology is a combination of the touchscreen interface with the controller. An “all-in-one” deal, the units have a touchscreen display (sometimes with adjacent hardware keys), and on the back of the unit are plug-in controller modules with I/O (input/output) connector clips.
Some “last, but not least” points to consider: HMIs, open HMIs, and panel PCs all have various levels of hardware options including add-ons like barcode scanners, CD/DVD players, microphones, and keyboard and mouse (if you don’t want to utilize the touchscreen). If you are going to need such add-ons, don’t assume that all HMIs are created equal. Check with the manufacturer first.
Don’t forget to pay attention to hardware certifications including Underwriters Laboratories (cULus), NEMA 4, NEMA4/12, IP65 (Panel Mounting Ratings), CE Certifications, RoHS listings, and Class I-Division II ratings (for the MicroOITs) — all good indications about the reliability and durability of the product.
Also, it’s helpful to utilize an HMI with configuration software that will let you test your application ahead of time on your PC to get a sense for its performance.
Perhaps the most critical aspect of any HMI display panel is to consider the technical support received when something goes wrong. An HMI glitch can literally mean a plant shutdown. Be sure your HMI provider has a good, long-term record of providing solid technical support with real engineers. Remember that the real price of an HMI includes the costs incurred when something goes wrong.
Also, don’t forget to check into your provider’s repair department. You don’t want to have your operation on hold while your HMI is being shipped overseas for repair.
The choices are many, but the wide range of prices and capabilities give you more options for both your budget and your automation goals. Just remember to first do your research on both the product and the company that provides it.
This article was written by Jeff Maki, Communications Specialist for Maple Systems Inc. in Everett, WA. For more information, Click Here .