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Smartrac Group and RFMicron to Develop Passive Sensor Tags

Smartrac will offer a new line of EPC Gen 2 passive UHF inlays containing antennas that act as sensors able to detect humidity, pressure and other conditions.
By Claire Swedberg
Apr 14, 2014

Smartrac has announced a partnership with RFMicron to create passive radio frequency identification tags with low-cost and simple, built-in sensors using what RFMicron calls its Chameleon technology. The tags resulting from the new partnership (announced at the RFID Journal LIVE! 2014 conference and exhibition, held last week in Orlando, Fla.) will enable users to read a tag's unique ID number, as well as the pressure or humidity conditions around the tag. Smartrac intends to begin releasing tags using the RFMicron chips for sensor functionality later this year.

Based in Austin, Texas, RFMicron was launched in 2006 by Shahriar Rokhsaz, the company's CEO. The firm spent several years developing chips that offer improved performance and inexpensive sensing capabilities. The result of that work, he says, is a passive ultrahigh-frequency (UHF) chip coupled with sensing circuits that detect a variety of environmental stimuli. Tags made with this chip will initially feature humidity and pressure sensors, but in the future, they could be used to measure temperatures and include other sensing capabilities as well, such as detecting specific fluids or gasses.

RFMicron's Shahriar Rokhsaz
As with all EPC RFID tags, the RFMicron IC, known as the Magnus S chip, harvests energy from UHF signals transmitted by an EPC Gen 2 tag. The Magnus S chip, however, has a self-tuning circuit that keeps a tag tuned in situations that would detune other tags, such as the presence of liquid or metal. This self-tuning feature provides two benefits, Rokhsaz says. First, it can be used to boost read rate. "The Chameleon self-tuning circuit will keep a tag tuned in situations where non-Magnus tags would normally be detuned," he explains. "In those situations, the Chameleon circuit allows more energy to be transmitted into the harvesting circuit." In addition, the on-chip sensing circuits monitor changes in humidity and air pressure levels, based on changes to the antenna's impedance—the measurement of the opposition that a circuit presents to a voltage current—resulting from changes in the amount of moisture or pressure to which the antenna is exposed. To improve tag functionality, the tag's received signal strength indicator (RSSI) circuit adjusts the chip's input impedance to correct for impedance mismatches resulting from these environmental changes.

In addition, the tag can share its sensor data with an RFID reader, providing users with information regarding the external environment around a tag.

The potential use cases cross many industries, Rokhsaz reports. For example, he says, a tag made with the Magnus S chip could be installed in tires to measure air pressure, thereby enabling owners of vehicle fleets to determine a given tire's inflation status via a simple RFID read. The same tag, embedded in tires, would also enable the firm to locate a specific tire, by using an RFID reader to search for that tire's unique ID number. In addition, an automotive manufacturer could utilize the tag to determine the moisture content of an object to which it is attached, so that the company could learn, during quality-control processes, if sensitive components were being exposed to excessive moisture levels.

The chip's pressure-sensing capability could be used to measure strain on buildings, bridges and steel, Rokhsaz says, and its moisture sensor could assess conditions that could lead to mold or mildew during construction, such as in dry wall.


Smail Tedjini 2014-04-20 03:53:11 AM
RFID tags as sensor : You can look to the publication http://digital-library.theiet.org/content/journals/10.1049/el.2013.3883
Peter Jonsson 2014-04-20 08:19:31 AM
Interesting. Though this is quite similar to another passive RFID moisture tag that been out on the market for a few years now, namely the TwinTag from Sensible Solutions.

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