By Jeremy Pollard, CET
I was driving down the highway one day, and noticed this unbelievable, gorgeous…BMW ragtop coming up behind me at quite a clip. As she blew by, I noticed that her bonnet was loose; it was a windy day and a gust could raise the roof, and boom.
So, as a Good Samaritan, I accelerated to catch up with her, and gave her hand signals to tell her that her hood wasn't closed. She thought I was being an idiot, telling her she was going too fast. She got away from me and moved into the slow lane.
Wow, I was totally misunderstood, and the hood problem still existed. Well, I tried.
Imagine an alarm system doing the same thing. "I really tried to let the operator know that the office was going to blow up, but he thought that the furnace just forgot to shut off."
Misconceptions, misinformation, and misleading and unsubstantiated comments lead to a load of misunderstanding. And then there are the omitted details.
Alarm systems are only as good as the clarity of the message. The messenger can only pass it on. This is where we fall down sometimes.
We are the message, regardless of what we are discussing. This message could be alarming, information passing, even marketing. This column is a message.
The reader question in August's Control Design (www.controldesign.com/portability) was about IEC 61131 standards-based software and portability. I get a little tweaked when I read IEC 61131 and standards together in the same thought.
The first time I witnessed a presentation on IEC 61131, the presenter held up a floppy disk (yes, that long ago) and said the software on it could be put into any "compliant" controller. Cool. No hardware loyalty required anymore?
Some of that regrettably simplistic misinformation still exists. Don't get me wrong, portability would be a reasonable objective, and it has been a goal of PLCopen for a while. The standard, however, does not address portability, but early vendor supporters ran with the idea. In North America, some vendors try to sell the idea of IEC 61131 in order to sell hardware.
You could argue that the marketing of IEC 61131 has been used against Rockwell Automation. After all, everyone knows that Rockwell Software is used only for Rockwell products. But all other hardware vendors' programming software also can be used only with their hardware.
Standards-based software has been around for a while. Visual Basic is one of the most popular. Ladder Diagram is somewhat standards-based due to the relay associations. IEC 61131 is based on a standard. Is there a difference?
Years ago, Borland C compiler and Microsoft's C compiler didn't use the same syntax, so you couldn't compile code directly. C language is universal, but not quite. Another commercial tombstone is WordPerfect. Microsoft's Word imported the file formats directly, and all but killed WordPerfect.
Although vendors talk about portability, I think most of them do not want to become a WordPerfect. That could happen if brand loyalty in hardware were diminished, since you could then (with software portability) hop from one vendor platform to another.
There will be no exporters of code, only importers. If a Siemens Step 7 program could be imported into Rockwell's Logix platform, would Siemens PLCs become redundant at some level? This could play into product pricing, distributor agreements, and the general automation economy.
The responses to the reader's question raised my blood pressure a bit because some sounded as if they were doing a sales job for the standard. I'll discuss those next month.
We, as users, are the messenger and the sheep herders. It is up to us to be exact in our explanations as best we can. We are everyone's alarm system, particularly regarding vendor claims.
We all need to take pride in the dissemination of accurate information.
Jeremy Pollard has been writing about technology and software issues for many years. Publisher of The Software User Online, he has been involved in control system programming and training for more than 25 years.