News from Profibus / Profinet – Part 5 PROFIBUS — Certification Ensures Compatibility
Billions of people use their cellphones without ever thinking about the underlying communications technology. The phones are made by different manufacturers, operate on different networks and have different user interfaces, but people can communicate no matter what phone they are using. PROFIBUS users also do not need to understand the details of the communications process, but they must have the assurance that all of the devices in operation meet certain criteria such as reliability, determinism and compatibility.
The youngster smiled when he had finished the first part of his presentation and it was time for the coffee break. Two weeks previously when he had been asked to give a presentation on the current state of automation at a gathering of former system operators and technical staff, he was not exactly excited about the prospect. However as he began preparing his presentation, he discovered that he really liked the topic and was now bursting with enthusiasm. During the coffee break, he intended to sit down at a table with two of the guests who had particularly attracted his attention. He approached the older of the two and following a brief discussion invited him to sit down along with the one with the beard at a vacant table near the edge of the room. He wanted to tell them a bit more about PROFIBUS compatibility and PA Profile 3.02. As he sat down, he placed his smartphone on the table in front of him …
Billions of people use their cellphones without ever thinking about the underlying communications technology. The phones are made by different manufacturers, operate on different networks and have different user interfaces, but people can communicate no matter what phone they are using. PROFIBUS users also do not need to understand the details of the communications process, but they must have the assurance that all of the devices in operation meet certain criteria such as reliability, determinism and compatibility. Both PROFIBUS equipment manufacturers and PI (PROFIBUS & PROFINET International) ensure that this is the case. Test labs accredited by PI perform exhaustive verification of the device communications interface before issuing a test certificate. This procedure ensures that all of the devices speak the same language and understand each other, in other words that they conform to specification.
Standard and Profile
PROFIBUS is standardized in IEC 61158, creating the framework for interoperability and compatibility. In addition, the PROFIBUS PA Profile facilitates smooth interaction between process devices on the bus. The current version V 3.02 contains many functions which make working with field devices even easier, for example device replacement. When a device is replaced, the spare device (which may well feature extended functionality) automatically assumes the role of the previous device, making device swap a simple operation which can be completed without interrupting system operation. Automatic adaptation also works with devices from different generations. The new device merely needs to support compatibility mode in compliance with Profile V 3.02.
A large number of manufacturers supply PROFIBUS products to the automation technology market. The product database at www.profibus.com currently contains more than 3,000 entries, 450 of which are specifically designed for process automation. As a result of standardization and certification, all of the devices work together without problems. Users can simply choose the device which best suits their needs without dependence on any one manufacturer.
“Replacing or adding a new device in a PROFIBUS PA string is not a problem,” said the youngster as he concluded his remarks. “It is almost as easy as replacing a glass which has fallen over on the table, possibly with one that has a more stable base!” “If necessary, I can knock over a glass even if it is more stable,” growled the man with the beard before continuing. “But you reacted in the right way, young man. Minor details like that do not bother a real system operator.” …
To be continued: Part 6
Further parts of our Profibus series:
Part 1: PROFIBUS – a Proven Technology
Part 11: PROFINET for Process Automation
Watch the video to find out more about the young engineer, the older man, the man with the beard and PROFIBUS PA.