Monthly Archive: May 2010

May
28

Deminar #4: On-line Process Control Lab Access and Use

I invite you to play the Recorded Deminar and download the presentation slides. The single, cascade, and feedforward loop labs are representative of 99% of the industrial processes if you scale the process gains, lags, and delays so that the controller gain setting is approximately the same and integrated errors are multiplied by a correction …

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May
20

How Fast Does Valve Position Communication Need to Be?

I got an excellent question during Deminar #3. An attendee asked how fast does the readback of actual valve position need to be as a secondary variable from a smart positioner. I said it depended on the speed of the valve. For flow loops, I thought once per second would be fast enough. However, since …

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May
13

Review of Deminar #3 – PID Control of Slow Valves and Secondary Loops (How to Eliminate Bursts of Oscillations with the “Dynamic Reset Limit” PID option)

You can click on the above to view and hear the recording of the Deminar. In Deminar #3 we explored the confusing situations that can develop for slow control valves and slow secondary loops. The loop can look fine but suddenly burst into oscillations and later go back to smooth sailing. The normal thought is …

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May
11

The Most Underutilized Component in Nearly Every Control Loop

If you look at all the features and options of a PID controller that are sitting idle, you realize only a small fraction of the power of the PID is used even if you make the big assumption that the controller is tuned. How many loops use integral deadband, nonlinear gains, dynamic reset limits, setpoint …

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