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Identification Systems
Introduction
8.1 Introduction
RFID stands for “radio frequency identification,” a wireless, noncontact
technology that identifies a person or object using a radio frequency
transmission, typically 125 kHz (low frequency) or 13.56 MHz (high
frequency). Typically, identification systems consist of a control unit, read/
write heads, and tags.
The tags are embedded or attached to an item where unique identification
and customer specific information can be saved. The read/write memory
areas can range up to 16 kbits. Read/write heads can read the tag and
modify the read/write portion as required by the application. This is done
with a series of commands sent from the PLC, to the control unit, to the
read/write heads, and finally, to the tag.
Several read/write heads can be connected to one control unit, which also
serves as the interface to the PLC/PC. Communication takes place via the
dominant industrial fieldbusses such as Ethernet, PROFIBUS, DeviceNet,
or via a serial interface. Wiring between the control unit and the read/
write heads is accomplished using shielded cables in order to reduce the
influence of EMC in the environment.
8.2 Frequencies
Two different frequency ranges are available and each has its advantages
and industries where it is often used: low frequency, 125 kHz systems and
high frequency, 13.56 MHz systems.
Low-frequency systems
The low-frequency systems typically have a few inches of read range, are
highly immune to metal in the environment and have good field penetration
of water, grease and other nonmetallic substances.The wound coil required
in a low frequency systemmakes the tag moderately expensive and typically
requires the tags to be reusable and not disposable. This frequency range
is typically used in factory automation, tool identification, closed loop parts
tracking, animal tracking and inventory control.
High-frequency systems
High-frequency systems* allow a smaller coil size, which makes the tag
less expensive. It is often used in logistical applications, asset tracking,
and select factory floor applications. The low cost makes this tag perfect
for high tag volume applications. Recent advancements allow these tags
to be embedded in metal and are, therefore, also appropriate for tool
identification. In addition to being low cost, they are up to 10 times faster
than the low-frequency versions.
*Available in ISO 15693 and 14443
8.3 High-Performance Components Offer
Maximum Flexibility
IDENT
Control
interfaces
The IDENT
Control
interface is the backbone of our latest RFID system
solution. It connects directly to your PC/PLC of choice and manages all
communications to and from the read heads. Read heads are configured
on power up, and parameters, like multiplex mode and tag type, are set
automatically.
The advantage is not merely the simplicity of the system, but the easy and
universal programming. No matter which head is used, the PLC or PC
programming is the same. All heads use the same commands and all tags
have the same addressing structure.
IDENT
Control
and IDENT
Control
Compact interfaces combine various
RFID technologies and frequencies into one device. The same device
operates high- frequency or low-frequency read/write heads and trigger
sensors - unifying operation and programming. You can connect four
read/write heads on one IDENT
Control
device—two read/write heads
on one IDENT
Control
Compact device—and configure them directly on-
site through integrated web servers, DIP switchs, or display and function
keys. Connecting to the web via Ethernet is no problem whatsoever. The
advantages: Several control units can be set up via one central network PC.
And, an SMS message is sent directly to you if your processes fail to run
smoothly due to a hardware error message.
Mixed Mode vs. Separated Mode
A feature that could make you choose one interface over another is the mode
of operation. You can read and write to all heads simultaneously. The key
difference is the memory mapping in the PLC. In the mixed mode operation,
all heads are mapped into the same PLC memory area. In separated mode,
memory is set aside for each head. Mixed mode is great for reducing bus
Interface
Read Head
Field
Tag
LF
(125 kHz)
HF
(13.56 MHz)
Identification Sytems RFID
8
Identification Systems RFID,
Control Interfaces
8
.1
Identification Systems RFID,
Heads and Transponders
8
.2
Identification Systems RFID,
Handheld
8
.3
Identification Systems RFID,
Accessories
8
.4
