It’s some time in the first decade of the 20th century. Speaking conceptually and totally speculatively, somewhere, at some factory, the first wireless set-up was being concocted by an enthusiast for that brand-new technology—radio. An operator located in production boonies with a transmitter the size of a refrigerator and a Morse code key feeds an operator listening to a receiver in the factory manager’s office.

A century later, everything (outside of modulation of electromagnetic waves) has changed. The radio now would fit in a pack of gum. The antenna is half a hand-span long or less, not two stories high. Data rates are bytes per millisecond, not 20 seconds per word.

Though it seems to go unrecorded, some time in modern memory, wireless technology was employed in a point (or, more accurately, point-to-point) solution for a sensor. Before long, point-to-point radios covered both simple sensors (1/0, on/off) as well as more complex sensors and instruments, the latter transmitting ranges or multiple data layers.

Today, there is a continuum of approaches to wireless installation. It is rapidly becoming the medium of choice over wired installations, particularly where remoteness, equipment motion or mobility—or the economics of running wires—make a radio a good solution.

On one end of this continuum, there is a 10-minute installation of a simple sensor, broadcasting its data, its own way and across a radio band all its own. On the other, there is a huge network of sensors and instruments neatly dovetailed into a complex network that has been hammered out over weeks of design.

Given this broad continuum, there is no one right way to set up and harvest useful data from radio waves transmitted from sensors or instruments. As in all of manufacturing, it all depends. This article explore some of these dependencies at three points on the continuum: (1) the simple one-radio, one-sensor installation; (2) a middle-level set-up in a distributed control scenario; and (3) a sophisticated setting where enterprise planning and enterprise information technology (IT)) is the backdrop.

Table I presents some of the key parameters for each of these three positions on our continuum.

In a simple set-up, a sensor is connected to a controller or programmable logic controller (PLC) with a radio transmitter instead of physical wiring. Anything the wires would have done is now handled by the radio.

A tad more complex is a set-up that involves multiple radio/sensors that incorporate mesh networking, but this, too, can be set up quickly. Here, each radio is capable of routing signals automatically. Because a mesh network is dedicated to delivering the message to the end point, it can handle interruptions, yet still deliver the sensor reading. It is self-healing in that it can route signals around glitched or down nodes along the network.

“There’s too much fear around wireless,” says Phil White, chief technical officer of IOSelect Inc., an instrumentation manufacturer based in San Diego. “You can try something simple, quickly and relatively inexpensively. [Up to a point,] you can use one form of wireless next to another form and they will both work happily for years. If they don’t work, you don’t need to feel locked in. You can always change things.”

White’s approach is, like his company’s offerings, eclectic. Among many net and connectivity devices, IOSelect markets equipment designed to carry signals back from remote mesh networks via Ethernet radio to central control areas, “sometimes 10 to 20 miles down the road,” White explains. “Digital, analog, serial, all are in our bailiwick,” he says, and the equipment is designed to interface directly with a broad range of computers, PLCs and distributed control systems (DCS). “Very few of our customers are installing entire infrastructures. They’re trying to gather data that’s miles away, or they’re trying to put several radios in a big metal room full of lots of mechanical equipment.”

At this relatively uncomplicated end of the wireless sensor spectrum, problems and solutions are again, relatively crisp and clear-cut. “In many situations, you can do a fast, ad hoc site survey with portable radio equipment,” White says. “If things get more complex, find someone with experience and equipment for more thorough surveys.”

Paul Brooks, business development manager, networks portfolio, for Rockwell Automation Inc., an automation supplier in Milwaukee, points out a basic consideration. “Whether your system is simple or complex, equipment decisions depend on data rates,” Brooks says. “A photocell is a simple sensor, but if it’s monitoring an airport baggage handling system, its single-digit transmissions might be continuous at millisecond rates. ...