The use of Ethernet communications in industrial applications is growing because it enables the real-time exchange of information between processing equipment and companies' Ethernet-based management systems. Some of the factors encouraging the use of Ethernet technology include:
- the speed advantages over lower baud rate protocols
- the number of tools available for troubleshooting and optimizing a network,
- the broad base of competitive vendor support and solution options and
- the large pool of trained personnel who are familiar with the technology.
In addition, the ability to bridge existing proprietary communications schemes makes it possible to phase in the use of Ethernet rather than having to replace everything at once.
When asked, engineers most frequently respond that they expect to use Ethernet to integrate control systems in the future. But a follow-up question, inquiring which Ethernet protocols they plan to use, is often met with confusion since some do not realize there are thousands of protocols that are compatible with, and can coexist on, Ethernet networks.
In attempting to navigate this sea of protocols, it is natural to look first to familiar ones that offer the functionality we are used to using on office networks, at home and on the Internet. Using such protocols, Ethernet can extend access to remote users through web browsers and e-mail. But for an engineer tasked with automating a process, the challenge is to connect devices to other devices to integrate automatic functions. For example, a temperature controller may need to get its set point from a programmable logic controller (PLC).
Ethernet protocols such as HTTP, which allows web browsers to display web pages, and SMTP by which email messages are transmitted, are ill-suited for the purpose of automation. These protocols are designed to transmit information over Ethernet, but the information is in a form that requires human interpretation. One purpose of automation is to relieve humans of the tedious task of monitoring and adjusting a process based on feedback from sources such as pressure gauges and mercury thermometers that require human interpretation. Another purpose of automation is, of course, to improve process results by removing variations in human interpretations and occasional misinterpretations from the process.