RFID Frequently Asked
Questions
What
is Radio Frequency Identification (RFID)?
How
does RFID work?
What are the Key Components to an RFID
System?
What
is an RFID tag?
What
is a "smart label"?
What is the difference between low-,
high-, and ultra-high frequencies?
How do I know which frequency is right for my
application?
What's the difference between passive and active
tags?
What’s the difference between read-only and
read-write tags?
What is the read range for a typical RFID tag?
What is Radio Frequency Identification (RFID)?
RFID stands for radio frequency
identification. It is an automatic identification technology, which uses
wireless radio communications to uniquely identify objects or people, and is
one of the fastest growing AIDC technologies. Similar to bar code
technology, RFID creates an automatic way to collect information about a
product or transaction quickly, easily and without human error. However,
unlike barcode technology, it provides a contactless data link, without need
for line of sight—for example articles inside a cardboard box—or
concerns about harsh or dirty environments that restrict the use of bar
codes.
How
does RFID work?
RFID uses an integrated microchip and antenna
that reads information. The combination of the chip and antenna is called an
RFID transponder or tag. There are two types of tags, and therefore two
types of systems, active and passive. In a passive
system, which is the most common, an RFID reader transmits an energy field
that "wakes up" the tag and provides the power for the tag to
operate. In active systems, a battery in the tag is used to boost the
effective operating range of the tag and to offer additional features over
passive tags, such as temperature sensing. The radio waves that are sent
back and forth between tag and transmitter contain the data in the tag, and
this data is then converted by the reader and transferred into a computer
system.
What
are the Key Components to an RFID System?
Included in a RFID system are a
number of components including tags, handheld or stationary readers,
antennas, and system software.
An RFID tag consists of a microchip attached to an antenna. RFID tags are
developed using a frequency according to the needs of the system including
read range and the environment in which the tag will be read. Tags are
either active (integrating a battery) or passive (having no battery).
Passive tags derive the power to operate from the field generated by the
reader.
An RFID reader, usually
connected to a Personal Computer, serves the same purpose as a barcode
scanner. It can also be battery-powered to allow mobile transactions with
RFID tags. The RFID reader handles the communication between the Information
System and the RFID tag.
An RFID antenna connected to the
RFID reader, can be of various size and structure, depending on the
communication distance required for a given system’s performance. The
antenna activates the RFID tag and transfers data by emitting wireless
pulses.
The System Software collects,
permutes and stores the data collected from the tag. This is usually similar
to any other data collection software.
What
is an RFID tag?
RFID tags consist of an integrated circuit
(IC) attached to an antenna-typically a small coil of wires-plus some
protective packaging (like a plastic card) as determined by the application
requirements. RFID tags can come in many forms and sizes. Some can be as
small as a grain of rice. Data is stored in the IC and transmitted through
the antenna to a reader. RFID tags are either "passive" (no
battery) or "active" (self-powered by a battery). Tags also can be
read-only (stored data can be read but not changed), read/write (stored data
can be altered or re-written), or a combination, in which some data is
permanently stored while other memory is left accessible for later encoding
and updates.
What
is a "smart label"?
"Smart labels" are a
particularly innovative form of RFID tag and operate in much the same way.
However, a smart label consists of an adhesive label that is embedded with
an ultra-thin RFID tag "inlay" (the tag IC plus printed antenna).
Smart labels combine the read range and unattended processing capability of
RFID with the convenience and flexibility of on-demand label printing. Smart
labels also can be pre-printed and pre-coded for use. In on-demand
applications, the tag inlay can be encoded with fixed or variable data and
tested before the label is printed, while the label can contain all the bar
codes, text, and graphics used in established applications. Smart labels are
called "smart" because of the flexible capabilities provided by
the silicon chip embedded in the tag inlay. A read/write smart label also
can be programmed and reprogrammed in use, following initial coding during
the label production process.
What
is the difference between low-, high-, and ultra-high frequencies?
Just as your radio tunes in to
different frequency to hear different channels, RFID tags and readers have
to be tuned to the same frequency to communicate. RFID systems use many
different frequencies, but generally the most common are low- (around 125
KHz), high- (13.56 MHz) and ultra-high frequency, or UHF (850-900 MHz).
Microwave (2.45 GHz) is also used in some applications. Radio waves behave
differently at different frequency, so you have to choose the right
frequency for the right application.
How
do I know which frequency is right for my application?
Different frequencies have
different characteristics that make them more useful for different
applications. For instance, low-frequency tags are cheaper than ultra high
frequency (UHF) tags, use less power and are better able to penetrate
non-metallic substances. They are ideal for scanning objects with high-water
content, such as fruit, at close range. UHF frequencies typically offer
better range and can transfer data faster. But they use more power and are
less likely to pass through materials. And because they tend to be more
"directed," they require a clear path between the tag and reader.
UHF tags might be better for scanning boxes of goods as they pass through a
bay door into a warehouse. It is probably best to work with a consultant,
integrator or vendor that can help you choose the right frequency for your
application.
What's
the difference between passive and active tags?
Active RFID tags have a battery,
which is used to run the microchip's circuitry and to broadcast a signal to
a reader (the way a cell phone transmits signals to a base station). Passive
tags have no battery. Instead, they draw power from the reader, which sends
out electromagnetic waves that induce a current in the tag's antenna.
Semi-passive tags use a battery to run the chip's circuitry, but communicate
by drawing power from the reader. Active and semi-passive tags are useful
for tracking high-value goods that need to be scanned over long ranges, such
as railway cars on a track, but they cost a dollar or more, making them too
expensive to put on low-cost items. Companies are focusing on passive UHF
tags, which cost under a 50 cents today in volumes of 1 million tags or
more. Their read range isn't as far -- typically less than 20 feet vs. 100
feet or more for active tags -- but they are far less expensive than active
tags and can be disposed of with the product packaging.
What’s
the difference between read-only and read-write tags?
Microchips in RFID tags can be
read-write or read-only. With read-write chips, you can add information to
the tag or write over existing information when the tag is within range of a
reader, or interrogator. Read-write tags usually have a serial number that
can't be written over. Additional blocks of data can be used to store
additional information about the items the tag is attached to. Some
read-only microchips have information stored on them during the
manufacturing process. The information on such chips can never been changed.
Other tags can have a serial number written to it once and then that
information can't be overwritten later.
What
is the read range for a typical RFID tag?
The read range of passive tags
(tags without batteries) depends on many factors: the frequency of
operation, the power of the reader, interference from metal objects or other
RF devices. In general, low-frequency tags are read from a foot or less.
High frequency tags are read from about three feet and UHF tags are read
from 10 to 20 feet. Where longer ranges are needed, such as for tracking
railway cars, active tags use batteries to boost read ranges to 300 feet or
more.
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