Sidebar: Smart Sensoring -- How It Works

Computerworld - One of the most recent applications of today's smarter, energy-saving sensor networks is on the Ben Franklin Bridge, which spans the Delaware River, linking Philadelphia and Camden, N.J.
The bridge carries automobile, train and pedestrian traffic. Bridge officials want to measure the strain on the structure as high-speed commuter trains cross.
MicroStrain Inc. installed a series of 10 smart sensors, which they programmed to "sleep" most of the time. The sensors wake up only when they sense a train approaching.
"If we were trying to monitor high data rates all of the time, we'd basically be flooding the system with information that wouldn't be important," explains MicroStrain President Steve Arms.
There also are power advantages to the sleep-mode arrangement. "The sensors will last one year in this sleep mode. Otherwise, they would have lasted a period of weeks at best," he says.
Arms credits the ability to fine-tune sensors' activities not to the sensors themselves, but to rapid advances in microcontrollers, which "are getting so powerful that they can be programmed to do a lot of different things. Having software sensibility on the node itself is really what you want. Having that software flexibility is critical," he says.
Indeed, it is what will allow the Delaware River Port Authority to conduct a trial under which it will use a cell phone network to access the sensor network on the bridge and reprogram the way it measures and transmits strain data.
As more programmable intelligence is built into the sensors themselves, Arms envisions end users taking greater control of the sensor networks they install. "We want to enable our customers to go in and reconfigure nodes with the intelligence they want them to have," he says.
For example, they may choose to have the sensors transmit data only when conditions are out of a preset normal range. "What this means is a great reduction in the amount of radio-transmitted data," Arms says. "Rather than have nodes [continuously] transmit lots of information, they'll transmit classifications of data. Then, alerts or alarms can trigger an e-mail or cell phone call for an engineer to come and take a look."

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