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Photoelectric Sensors
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Photoelectric Sensors
Introduction
7. Optical Data Couplers
Optical data couplers are used for the cable-free
transmission of information via modulated light
between two points along a line-of-sight axis. Unlike
RF-based communication, the modulated signal is
immune to noise interference. And they replace
mechanical means of data transfer like slip rings and
drag cables that are susceptible to noise and offer little flexibility.
For optical transmission, the FSK method (Frequency Shift Keying)
is used. In other words, the bit information is coded in the carrier
frequency.
The emitted signal is shifted between two frequencies, f1 and f2,
that correspond to either logic bits 0 or 1. Narrow band filtering,
used on the receiver side to convert the data back to logic, prevents
extraneous signals from corrupting the transmitted data. The data
transmission is unaffected by signal level variation.
f
1
f
2
log „0“
log „1“
Pepperl+Fuchs offers optical data couplers for parallel as well as
serial data transfer.
•
Parallel data transfer:
An optical data coupler can transfer eight bits bidirectionally. To
do this, the signals in the device are converted into a serial bit
sequence. The data is then applied to the parallel outputs in the
receiver. FSK modulation, which is noise-resistant, is used to
transfer the binary signals.
•
Serial data transfer:
Our serial optical data couplers also use the FSK method. The
data that is available at the interface is transferred protocol free
and is then converted again at the serial interface. Many optical
data couplers with serial interface are also available with visible
red light transmitters. These devices are used with infrared data
couplers to prevent cross-talk between data routes when used
in close proximity to each other.
8.
Our guarantee for safety and reliability
The new generation of photoelectric sensors with the features
you need today - economical, easy to install, and reliable in harsh
environments.
•
Highly visible LEDs
•
Enhanced status LED indications
•
Modern outputs such as 4-in-1 or AS-Interface 2.11
•
High ambient light resistance
•
Cross-talk immunity
