Redefining Sensors

E-mail Tom Kevan

In most cases, basic sensing technology is mature and unlikely to change much. But don't get too comfortable; the concept of what constitutes a sensor is changing drastically. New capabilities are being added to enable these familiar devices to take on new applications.

Adapting to the New Landscape
The earliest sensors just measured physical properties and produced an analog signal. Then fieldbuses and wired networks came along, and digital data became the lingua franca. This required sensors to convert their analog signal to a digital format. More than that, though, sensor manufacturers had to buy into a whole new world view: The sensor could no longer take a local view, but had to be part of a bigger picture. Communications were now part of the process, and sensors had to accommodate the shift.

This evolution began as sensors were slowly integrated into networking environments. The fieldbus wars calmed down, and sensor manufacturers grew increasingly comfortable dealing with communications considerations. On top of that, the folks at IEEE introduced the concept of the smart sensor. This trend is gaining momentum, and the attributes ascribed to smart sensors are the prelude of things to come.

The Wireless Dimension
With the growing presence of battery-supported wireless sensors, new demands are placed on the once simple devices. Although working with radios adds another level of complexity, the biggest change is brought on by the tighter energy budget required by battery power. To adapt to this new world, future sensors will have to be "smarter" and more efficient.

For example, sensors must turn on and stabilize quickly to minimize power consumption. In addition, the number of measurements must be reduced to the minimum called for by the application. This second requirement means that more logic has to reside on the sensor to control duty cycling, and the device must also have its own data storage.

Scott Pape, Microcontroller Division Systems Engineer for Freescale Semiconductor, observed, "You will see more integration of logic with analog sensors to give them more capability to take measurements on their own, to have time bases that allow them to turn on, take a measurement or series of measurements, store the data on RAM embedded on the sensor itself, and then shut off."

Rob Conant, co-founder and vice president of marketing and business development for Dust Networks, supported this view by saying, "The sensing element itself is either duty cycled or not. In many traditional sensor applications, the sensor is on all the time. But with the advent of the wireless sensor networking technology, more people are looking at extremely low power consumption, in which case people are starting to have to duty cycle those sensors."

The New Sensor
As sensors adapt to meet changing and growing demands, their overall performance will become more efficient, both in terms of functionality and energy consumption. For many applications, the simple device that only measured physical properties will become a thing of the past. The new sensor will be able to autonomously control its own complex operations and interface with systems that will enable it to communicate with the outside world.

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