Real-time

Lets get specific!

Real-time Different things to different people?

What do we mean by real-time, and what use it anyway? We explore this question and come up with some interesting insights.

I was once told by an excited accountant that he had just installed a networked package and he was now getting the information of his corporate sales in real-time. "Yes" he said proudly, "I am informed of every transaction that takes place in any one of our offices around the country within a period of just 24 hours!"

Several months later, I was told by an engineer on a bottle production line that his system was not really real time because it only updated every 100 milliseconds!

Later I heard a computer programmer tell me that real time trends are what are held in memory whereas historical trends are what are stored on the disk or in a database.

So what is "really real-time"? Wouldn't it be convenient to say that anything faster than 1.3456 seconds update rate is real-time and anything slower is not!

Or can we define Real-time as something more absolute?

Unfortunately as the above three examples clearly demonstrate, the definition of real-time is a little slippery. We thought about the subject and came up with this definition:

Something can be said to be working in real-time when the time constants of the measurement and control loop are insignificant compared to the time constant of the process.

In fact, it has nothing to do with the person's subjective viewpoint or even the way the information is stored or manipulated in the computer. It has everything to do with the time constants and dynamics of the process. This brings us firmly back to where we as engineers should be. Thinking about the process and not semantics!

And yet, all too often, it is the semantics that drive our day to day thoughts. (Not only in engineering but in all walks of life!) Even though the only way to get real-time trends in the 70's was to store the data in memory, it does not mean that we have to continue doing this today. We look around and yes things have changed! Let's continue to question the words we use and the perceptions we have so that we can continue to create brilliant Industrial Software!

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