The days of manual pushbuttons, analog meters, and clipboards to control, track, and record plant floor conditions are rapidly drawing to a close. Today, operators are able to exercise control and record operational history via modern, operator interface video panels. The term "operator interface" is a bit of a misnomer, as it suggests that the product is little more than a relatively "dumb" c...
The days of manual pushbuttons, analog meters, and clipboards to control, track, and record plant floor conditions are rapidly drawing to a close. Today, operators are able to exercise control and record operational history via modern, operator interface video panels.
The term "operator interface" is a bit of a misnomer, as it suggests that the product is little more than a relatively "dumb" control panel, dependent on remote processors for any computational duties. In fact, most of today's display panels are integrated with industrially hardened personal computers, many of which are capable of running the same software used in control rooms. Commands are entered via touchscreen, keyboards, or dedicated keypads.
Operator interface panels range from compact monochrome screens measuring as little as 3 or 4 inches and performing only very basic control functions up to dazzling color, thin film transistor (TFT) touchscreens, 17 inches or larger, with 256 megabytes of memory, multiple communications protocols, and Intel Pentium processors.
With such a variety of products to choose from, following are a few key factors buyers should consider before making a purchase:
Does the product meet requirements? For many users, panels that provide only the most basic levels of machine and device control are perfectly sufficient for their needs. Others, however, may want to purchase more sophisticated, flexible devices to meet current or anticipated future needs for control functionality, networking, or reporting.
Integration with existing systems : Vendors that provide a range of plant floor products and systems as well as operator interfaces typically suggest that users consider their overall plant architecture when selecting operator interfaces. Not surprisingly, these vendors also tout smooth integration of their interfaces in plants already using their software and hardware.
Software and operating systems : Some vendors' interfaces are based on proprietary operating systems and software. For many users concerned only with controlling or monitoring an isolated machine, the underlying software architecture is not an issue. Many vendors, however, offer panels designed to run on widely used industrial platforms, such as Microsoft Windows XP or Windows CE. While interfaces based on less-widely used platforms can be less expensive than more-accepted products, users will be limited in choice of application software and the ability to integrate with other systems. In addition, support personnel proficient in Windows-based systems aren't hard to find.
Communications capabilities : Connectivity among plant floor systems and between the plant floor and business level systems is becoming increasingly important. As a result, buyers should consider the communications capabilities of operator interfaces. Among features to consider are whether they: support standard industrial protocols, such as OPC, TCP/IP, and high-speed Ethernet; have built-in Web servers for remote viewing of reports; and are able to automatically send email if an event, such as a machine shutdown, occurs.
Ease of use : For operators with limited computer experience, this feature is vital. In addition, buyers should consider the ease with which they can create new operator screens. "Creating screens should be as simple as creating a PowerPoint presentation," says Greg Philbrook, AutomationDirect's HMI/communication product manager. In addition, consider the online support capabilities of any product under consideration. For example, some operator interfaces include PDF user manuals that can be read onscreen, while others provide contextual "help" screens.
Reliability : In many plants, operator interfaces are exposed to extremes of temperature, vibration, humidity, particulates in the air, and other punishing environmental factors. With this in mind, users should consider a product's overall reliability, using measurements such as mean time between failure, as well as suitability for particular conditions.
Availability of support : Users should carefully examine availability of local support for an operator interface and vendors' support policies—for example, what components are covered by support, warranty terms, and length of time vendor plans to support a product.
Price is a major consideration in the purchase of operator interfaces. The simplest devices with small, monochrome screens and 256K of internal memory and very limited communication capabilities can be purchased for $500 or less. Prices rise gradually with the addition of TFT color displays, additional memory, additional networking capabilities, and application software. High-end products, such 15-17-in. touchscreens with 256 megabytes of memory, Windows CE, flash storage, and multiple communications protocols, can cost $7,000 or more.
Prices can also vary based on the need to meet specialized plant conditions. For example, in facilities with a great deal of airborne particulates, such as paper mills, operator interfaces, should be fanless to minimize intrusion into the devices' electronics. For similar reasons, such units should rely on flash memory rather than rotating media for data storage.
In the food and beverage industries, operator interfaces must be made of stainless steel or be placed in enclosures that can be washed down. In FDA-regulated industries, such as pharmaceuticals, interfaces may be called on to record and communicate a complete history of operations to comply with traceability requirements. If an operator interface is located outdoors, buyers need to ensure that screens are bright enough to read in sunlight.
Operator interface checklist
Does the power, flexibility of the product match requirements?
How's the data-sharing ability? How does look-and-feel compare to existing plant products/systems?
Is operating system open or proprietary?
How are communications capabilities?
Is it easy to use? Touchscreen?
What's the reliability or mean time to repair?
Is local support available?
Are there industry-specific needs (washdown in food and beverage; traceability for pharmaceuticals)
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