TABLE OF CONTENTS There are several ways to classify industrial networks. Each form of classification has utility for certain industries, applications, or standards bodies.
Networks used in industrial automation may be classified by the type of application:
process control
materials handling
motion control
discrete automation
They can also be classified by the type of data they transport:
ON/OFF data expressed in bits or bit strings
scalar data representing engineering units values
general database exchanges
Finally, they can be classified by level of automation:
sensor level
field level
control level
information level
With the convergence of network protocols and multiple uses for networks, none of these classifications are very productive. However, there are networks designed for efficiently transporting certain types of industrial automation data. This discussion will use these network classifications, with the following titles:
discrete sensor data
process control fieldbus
control-level networks
information technology (IT) networks
Discrete sensors such as limit switches, proximity switches, level switches, and relays of all types as well as simple actuators such as solenoid valves and motor contactors are represented by one binary bit of data. Networks designed for the distribution and collection of data to and from these types of devices usually have nodes that concentrate data from several such devices at one location: the network connection hub. Wiring for these networks focuses on reducing the cost of connection to control I/O equipment. Typically, little or no signal conditioning or data processing is possible at the network connection...
