What is RFID ?
stands for radio frequency identification. This is a complementary
technology to bar codes. RF tags, or "transponders" (from
TRANsmit-reSPOND), can be used to carry data about the things to
which they are attached. Thus we see RFID technology applied in
livestock farming (to trace the history of each animal), car manufacturing
(build history of each vehicle) and freight (shipping manifests),
to name a few applications.
RF Tags - There are two general types, passive and active. Active
tags have a built in power cell and have a higher communication
range, but a life limited to the life of the power cell. Passive
tags carry no on-board power, but derive it from the reader, giving
them a practically unlimited life but a shorter range.
For most general applications passive tags are usually the most
cost effective. These are made in a wide variety of sizes and materials:
there are durable plastic tags for discouraging retail theft, wafer
thin tags for use within "smart" paper labels, tiny tracking
tags which are inserted beneath an animal's skin and credit card
sized tags for access control. In most cases the amount of data
storage on a passive tag is fairly limited - capacity often being
measured in bits as opposed to bytes. However for most applications
only a relatively small amount of data usually needs to be codified
and stored on the tag, so the limited capacity does not normally
pose a major limitation. Most tags also carry an unalterable unique
electronic serial number which makes RFID tags potentially very
useful in applications where item tracking is needed or where security
aspects are important. The read/write range depends on the tag's
type, active tags generally having a longer range than passive tags.
For passive tags the most critical range aspect is the type and
size of the reading antenna.
- There are three frequency ranges
in RFID systems. Low frequency (100 to 500kHz) is the least expensive
and has a low reading rate at short to medium distances; typical
uses include vehicle immobilising, livestock identification and
access control. Intermediate frequency (10 to 15MHz) has a medium
reading rate at short to medium distances and is ideal for smart
cards. High frequency (850 to 950MHz, 2.4 to 5.8GHz) has the fastest
reading rate and long range capability, but requires a line of sight
between the reader and tag and is the most costly option; a typical
application is automated toll collection.
Reading and Writing Tags
- RF tag readers range
from desk top devices to hand held computers which can be used to
write data to the tags as well as to read them. The choice of reader
will depend on the type of application. For example, will it be
in a fixed position or does it need to be portable?
Consideration needs also to be given to the type of tags. There
are many manufacturers of RF tags and there has been little compliance
from one manufacturer to another. Efforts are being made to introduce
global standards and some form of uniformity is expected to come
about in the next few years.
- The term "Smart Labels"
basically refers to super thin RFID tags that are embedded into
otherwise conventional labels. From an application point of view
the real benefit of Smart Labels is the potential to combine human
readable printed data with data storage capability and possibly
bar code reading capability by printing a conventional bar code
on the label as well. Being able to combine these three forms of
readability with RFID "writeability" opens up a range
of opportunities for low cost tracking and traceability. Some thermal
transfer label printers are now becoming available with the additional
facility to write data to a Smart Label at the same time that the
label is printed.
Putting together systems
- RFID is a specialised
but rapidly expanding field. Organisations requiring RFID solutions
need to work closely with a systems provider which has in-depth
knowledge of the technology and is able to create a complete solution
which fits the customer's needs.