Can we track the whereabouts of our dog wearing a passive microchip?

Yes, but you need to keep him on a very special leash.

By Meg Murphy

Last summer a Siberian husky named Raven escaped a family yard in Nebraska and was identified in Illinois. A Yorkshire terrier called Zeus was dog-knapped in Florida and located in Michigan. Eddie, a Yorkie too, was discovered after disappearing from a family function in Manchester, England six years ago. He was living with a woman nearby.

These dogs all had something common: an implant. A popular tracking device — a passive microchip and an antenna, together called an RFID tag— had been injected in the skin beneath between the dog’s shoulder blades. The tiny computer chip, approximately the size of a grain of rice, has an identification number programmed into it.

These dogs shared another key factor: they all came in contact with a hand-held device that transmits electromagnetic energy to the tag embedded in their implant. If they hadn’t landed at pet hospitals or animal shelters where concerned individuals had the equipment and know-how to scan them, they may never have been “found.”

The technology driving these devices is simple, says Sanjay E. Sarma, a professor of mechanical engineering, the Vice President for Open Learning at MIT, and a pioneer in the development of radio frequency identification (RFID) technology and industry standards. “A reader in the vicinity puts out a signal. It asks, ‘Who are you?’ The signal wakes up the chip, and it responds,” he says. (Again, a little more slowly: when radio waves transmitted from the reader reach the chip’s antenna, the energy of those waves is converted by the antenna into electricity that can power up the microchip in the tag; the tag then sends information stored on the chip back to the reader.)

So if a pet goes missing and ends up at clinic, animal shelter, or pound that has the right equipment, personnel can scan for a microchip and check a national registry. Then the owner gets a call.

Unfortunately, a passive RFIP microchip is not the same things as a GPS and it cannot act as a location device. “The microchip works as long as it is awake,” says Sarma. “There must be a reader close by. It’s not a location tracker.” It is, however, a useful ID tag that can be used to keep track of all kinds of animals: dogs, cats, cattle, and so on. “It has a very wide range of applications,” he says.

Sarma says “it’s sort of like a windmill,” in that a microchip responds to radio frequency like the mill does to wind. Nothing happens without it. “If the dog leaves the vicinity, that’s it,” he says.

Thanks to Catherine McGeachy, 61, from Limerick, Ireland, for the question.

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