Featured Research

from universities, journals, and other organizations

Passive Sensors Remotely Monitor Temperature And Stress

Date:
July 2, 2002
Source:
Penn State
Summary:
The same material that makes the theft detectors go off in a department store when the salesperson forgets to remove the anti-theft tag, may make inexpensive, passive temperature and stress sensors for highways, concrete buildings and other applications possible, according to Penn State researchers.

The same material that makes the theft detectors go off in a department store when the salesperson forgets to remove the anti-theft tag, may make inexpensive, passive temperature and stress sensors for highways, concrete buildings and other applications possible, according to Penn State researchers.

"These materials typically cost about $100 a mile and each sensor is about an inch long," says Dr. Craig A. Grimes, associate professor of electrical engineering and member of Penn State's Materials Research Institute. "Consequently, the sensors would cost just about nothing, or about a half cent apiece."

The material used in these sensors is an amorphous ribbon of alloy that is manufactured to be softly magnetic by quick cooling. One example is an iron, molybdenum, boron, silicon alloy. Magnetically soft materials have no strong fixed magnetic fields, even though they contain iron. In magnetically soft materials, the magnetic field switches back and forth depending on the environment and can generate many higher order harmonic frequencies.

"These magnetoelastic thin-film sensors are the magnetic analog of an acoustic bell," says Grimes. "When an externally applied magnetic field reaches the sensors, they ring like a bell, emitting both magnetic flux and acoustic energy with a characteristic resonant frequency." Just as a bell changes pitch and overtones when heated or cooled, the magnetoelastic thin-film changes magnetic response.

When a customer walks out of a department store with an anti-theft device still on a purchase, these metal strips set off an alarm because the sensors at the door sense the soft magnetic field. To use these strips as temperature and stress sensors, an activator must be passed near the sensor strips. Because the sensors operate passively and remotely, there are no wires or connectors required, so the sensors are simply and even randomly imbedded in the material to be sensed.

A simple loop that generates a magnetic field activates the sensor from a distance. This magnetic field is not blocked by the materials in the road surface or concrete and is not altered by any iron, such as rebar in construction concrete. Rebar does not have the magnetic properties needed to support the higher frequency harmonics. A figure-eight loop senses the strips' response, reading the harmonics of the strips magnetic field. These harmonics are like the overtones of the bell and change as the environment of the strip changes.

On roadways, sensor strips embedded in the road surface could indicate when temperatures are low enough for salt application, but not too low for the salt to do any good. In the case of buildings involved in earthquakes or other structurally altering events, the sensors can indicate a change in the stresses inside the concrete and help to determine if the building is safe for occupancy.

The strips need to be coated with a polymer to avoid corrosion, although if corrosion is the property to be sensed, then the strips should be either left uncoated to corrode or coated with an analyte responsive layer.

In a recent issue of Applied Physics Letters, Grimes, with Dale M. Grimes, professor emeritus of electrical engineering, and Keat G. Ong, postdoctoral fellow at Materials Research Institute, say that "we found the temperature response of 40 sensors to be experimentally identical." These simple sensor strips provide a consistent temperature reading.

Because the sensors are softly magnetic, their orientation in the materials relative to the activatoris unimportant.

These sensors can also be immersed in water or other liquids and provide not only temperature but also viscosity, liquid density and surface tension. Because the sensors are so inexpensive, their use in a wide variety of materials, sensing a wide number of properties, may be possible in the future.

Grimes has a patent on this work, which was supported by NASA and National Science Foundation.


Story Source:

The above story is based on materials provided by Penn State. Note: Materials may be edited for content and length.


Cite This Page:

Penn State. "Passive Sensors Remotely Monitor Temperature And Stress." ScienceDaily. ScienceDaily, 2 July 2002. <www.sciencedaily.com/releases/2002/06/020627005122.htm>.
Penn State. (2002, July 2). Passive Sensors Remotely Monitor Temperature And Stress. ScienceDaily. Retrieved July 28, 2014 from www.sciencedaily.com/releases/2002/06/020627005122.htm
Penn State. "Passive Sensors Remotely Monitor Temperature And Stress." ScienceDaily. www.sciencedaily.com/releases/2002/06/020627005122.htm (accessed July 28, 2014).

Share This




More Matter & Energy News

Monday, July 28, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

The Carbon Trap: US Exports Global Warming

The Carbon Trap: US Exports Global Warming

AP (July 28, 2014) AP Investigation: As the Obama administration weans the country off dirty fuels, energy companies are ramping-up overseas coal exports at a heavy price. (July 28) Video provided by AP
Powered by NewsLook.com
Europe's Highest Train Turns 80 in French Pyrenees

Europe's Highest Train Turns 80 in French Pyrenees

AFP (July 25, 2014) Europe's highest train, the little train of Artouste in the French Pyrenees, celebrates its 80th birthday. Duration: 01:05 Video provided by AFP
Powered by NewsLook.com
TSA Administrator on Politics and Flight Bans

TSA Administrator on Politics and Flight Bans

AP (July 24, 2014) TSA administrator, John Pistole's took part in the Aspen Security Forum 2014, where he answered questions on lifting of the ban on flights into Israel's Tel Aviv airport and whether politics played a role in lifting the ban. (July 24) Video provided by AP
Powered by NewsLook.com
Creative Makeovers for Ugly Cellphone Towers

Creative Makeovers for Ugly Cellphone Towers

AP (July 24, 2014) Mobile phone companies and communities across the country are going to new lengths to disguise those unsightly cellphone towers. From a church bell tower to a flagpole, even a pencil, some towers are trying to make a point. (July 24) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins