Q&A: Radio-frequency ID tags

Posted by Cameron Schwab on December 3rd, 2018

What are radio frequency ID tags?

They are small devices that store data that identifies the object to which they are attached. They have been called "smart barcodes" and are intended to take over many of the jobs of those ubiquitous black and white stripes.

The data onboard an RFID tag can be read at a distance via radio. They typically combine a small amount of computer memory with a radio antenna.

There are two types of radio frequency ID (RFID) tags: passive and active.

Passive tags have no battery onboard but the current generated when they are scanned with a radio reading device powers the tiny circuit and makes it emit a signal.

Because of this the data in passive tags can only be read over small distances - up to a few metres.

The small size of these tags- which often lack an antenna - mean they often only hold an identity number. The smallest passive tags are as thin as paper and about a quarter of a millimetre square - slightly larger than the full stop at the end of this sentence. Adding an antenna makes them much larger - about as big as a first class stamp.

Active tags are bigger, always have an antenna and are fitted with their own battery. These tags can be read over distances of hundreds of metres and have a lifetime of about a decade.

They hold much more data about the object or objects to which they are attached.

Active tags often have other sensors onboard that help monitor the object, such as a cow or volatile chemicals, to which they are stuck. In this way they could report the location of a cow if it wanders off or if explosive chemicals are getting too hot.

Why are they useful?

Barcodes have made big differences to business as they help to track goods, keep shelves stocked and ensure you pay the right price for what you buy.

RFID tags promise to do what barcodes do and add much more to it.

To begin with RFID tags make it much easier to keep an eye on goods as they move from where they are produced to where you buy them.

They make it possible to check what is on a particular lorry just by driving it through a really big reading device. Individual boxes no longer have to be scanned one-by-one.