RFID tags used to monitor temperature and humidity
A new study* by a team including a professor from North Carolina State University has found a way to implement wireless monitoring technology by tapping into a building's heating, ventilating and air-conditioning (HVAC) ducts.
The finding could lead to significant time and cost savings for applications such as temperature and humidity monitoring, since the systems can be put into place without the expense and effort of running wires throughout the buildings.
The researchers have used radio-frequency identification (RFID) tags that can be equipped with sensors that allow them to transmit information – such as temperature – back to a reader. RFID systems use centralised readers to collect data from relatively small, lightweight tags equipped with radio antennas.
In an RFID system, an electronic reader broadcasts a radio wave with a specific frequency. When an RFID tag receives the transmission it absorbs energy from that transmission, enabling it to respond to the reader by the way that it reflects the wave.
“This would work with anything you can create an electronic sensor for,” says Dr Dan Stancil, co-author of the study paper and professor and head of NC State's Department of Electrical and Computer Engineering.
The researchers used ultra high-frequency (UHF) RFID systems. When placed in open spaces, UHF RFID tags typically need to be within 5–10 metres of the reader in order to respond to a transmission. However, the researchers have found that, by tapping into a building’s HVAC system, UHF RFID tags can operate when located 30 metres or more from a reader.
For example, existing climate-control units have thermometers placed throughout a building, each of which is connected to a central climate-control monitor via extensive wiring. However, you could distribute RFID tags with temperature sensors throughout the building instead, with short antennas connecting them to the building’s HVAC ductwork. The tags would then send temperature data wirelessly to readers via the ductwork.
*The study was published in the September issue of Proceedings of the IEEE.
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