Smart sensors need their vitamin 'C'

Chicago—The real world is disappearing.

As engineering schools crank out computer-whiz graduates who are experts in software modeling, the schools graduate fewer hardware specialists. Back in the factories, machines are often fitted with sensors that no one knows how to use.

To compensate, the sensor industry is chasing a holy grail—smart sensors. "The goal is to make the system smart enough so you don't have to be an expert in the business to use the sensors," says Edward Herceg, national sales manager at Macro Sensors (Pennsauken, NJ).

"There's an enormous proliferation of electrical devices like microelectronics and microcontrollers, all of which need information. And there are only two ways to get it—either someone keys it in, or it comes from sensors," he told a crowd of 25 people at a session on "Electromechanical Sensors for the New Millennium's Manufacturing and Control Systems," at the National Design Engineering Show (NDES) at the McCormick Center here.

The typical circuit for a smart sensor shows information flowing from the interface (STIM) to a data sheet (TEDS) through a processor (NCAP) to the network.

"At the same time, the knowledge base of people who know how to use sensors and get measurements is continuously depleting. Today more people are software- and computer-oriented, not hardware-oriented, and schools are teaching people how to use software and do simulations on computers. But the real world is still touchy-feely. You've gotta get down and dirty, and to do that you need sensors."

The field is full of sensors with different strengths, including linear position sensors, rotary position sensors, pressure measurements, force/load measurements, and proximity sensors—inductive, capacitive, magnetic, ultrasonic, and photoelectric. With any of these choices, there are three reasons to use a sensor: making measurements, gathering statistical information, or controlling a process or equipment.

As digital signal processing chips proliferate, virtually every job is handled by digital processing, which allows a sensor to achieve the "Five C's." While there is debate about how much intelligence a sensor needs to become smart, Herceg says the most basic test is to have all five conditions:

connectivity, when it can hook up to various buses

communications, when it can identify itself to a host computer, store data, receive commands, prioritize information, and avoid slowing down the job

calibration, when it can do self-diagnostics and self-evaluation, and maintain an internal record

correction, when it is able to sense a problem in the operation and correct itself

compensation, when it can sense external factors such as environmental changes, and adjust its sensitivity

These abilities allow a sensor to operate under various conditions, and to be tuned and adjusted by engineers who don't need to know what's under the hood. "As companies become more lean and mean, they need these kinds of smart sensors," agrees Lee A. Bondy, president of Macro Sensors.

What's next? The biggest change in the field will be the completion of the IEEE 1451 standard, pending sometime this year, which will allow universal connectivity between sensors (or actuators) and control systems. Check www.ieee.org  for the latest.