Sensors Mag

App Snaps

June 1, 2006 By: Melanie Martella, Sensors Sensors

Healthier Building Control

Imagine that you are the facilities manager of a two-floor, 29,000 sq. ft. building with 88 rooms and no monitoring system. Every morning you check the weather forecast and adjust the temperature accordingly. Sounds like fun, doesn't it? That was the situation facing a Chicago health clinic. The clinic needed to monitor air temperature and energy usage but couldn't install a wired system because of building codes and the steep cost involved.

The clinic contacted TENG (, a company specializing in design and construction management services who, in turn, teamed up with Dust Networks, a company specializing in wireless mesh networking, and Tridium Inc., creator of software to integrate diverse systems and devices (

Dust Networks provided the SmartMesh components for the wireless sensor network, consisting of 41 temperature sensors and five current sensors, while Tridium's Niagara software allowed real-time control from a standard Web browser. According to Fran Donohue, operations manager for TENG, "With a wireless mesh network, deploying an air temperature monitoring solution was easy. It would have taken my team four man weeks to install those 46 nodes using a wired solution, but with SmartMesh it took us less than two hours."

Contact Dust Networks, Hayward, CA; 866-289-3878,,

Volcanoes vs. Jet Engines

At any given time, 20 volcanoes are erupting somewhere on the planet. Volcanic ash and jet engines do not mix well. This wouldn't normally be a problem, but on Unimak Island in Alaska there are six volcanoes, one of which, Shishaldin, has erupted at least 29 times since 1755. Unimak lies under one of the heavily traveled North Pacific air routes. Unfortunately for the pilots, the island's topography and lack of populated regions close to the volcano severely limit visual observations, forcing the pilots to rely on acoustic, seismic, and satellite data to understand Shishaldin's behavior and give early warning of plumes of dangerous ash.

Volcano eruptions can be Strombolian (characterized by lava) or Subplinian (characterized by plumes of ash); the trick is to figure out which kind of eruption is about to occur.

Seismologists with the Alaska Volcano Observatory check data on the 44 Alaskan volcanoes to pinpoint which ones are about to erupt and collect data to correlate sensor signals to volcanic behavior. In 1999, one of their tools was a Setra 239 pressure sensor mounted on the eastern side of the instrument hut in clear view of the summit of Shishaldin and used to detect the infrasonic oscillation generated whenever the volcano erupted. Jackie Caplan-Auerbach, a seismologist with the observatory, says, "Shishaldin exhibited an unusually wide range of eruptive behavior over a period of four days. Data collected by the pressure sensor provides us with new insights into this eruption, with its unique combination of lava flow and ash plume. . . . The Setra 239 was able to detect what was happening inside the volcano before the eruption occurred. It was able to pick up signals and record information that the seismometers could not."

Contact Setra Systems Inc., Boxborough, MA; 800-257-3872,,

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