Industrial Data Communications
Field Bus
These days, most field
devices can be connected via a bus system. A large amount of machine
wiring can be avoided by the appropriate use of data communications
technology to connect switches, sensors and actuators back to the PLC. Bus
technology can be simple like the ASI standard for replacing traditional
input/output cards or more complex, like ProFiBus-DP which allows larger
volumes of data to be exchanged between the PLC and devices such as
temperature controllers and motor drives.
PLC to PLC Communications
Larger control systems often
involve more than one PLC, especially if sections of the production
equipment need to be able to operate autonomously. However, it is likely
that these will still need to communicate to allow seamless factory
automation. For higher level communication there are many options, such as
ProFiBus-FMS, ControlNet and industrial Ethernet with a whole range of
different protocol choices. We have implemented a large number of these
and have found solutions for heterogeneous environments that employ
multiple vendors' systems.
PLC to PC Communications
The Windows PC is becoming
used more and more as part of a control system, providing a graphical
display on the machine or for interfacing production systems to the
corporate network and MRP system. Data must be read from or written to the
PLC without risk to the safe and proper functioning of the control system
and sometimes large volumes at high speed. This is an area in which we have a lot of
experience, particularly for interfacing to our data collection systems
and production monitoring projects.
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