Is the Harris Index Right for Your Loop Assessment Needs?

Predicting the weather is difficult – just ask a meteorologist. Even with the help of advanced analytics few seem to get it right with consistency – just ask any parent who has dealt with an unplanned snow day. In addition to more advanced tools meteorologists rely on basic measures such as Temperature, Wind Speed, and Atmospheric Pressure. Their continued reliance on these simpler metrics provides food for thought.

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Data Collection Speed is Key to the Accurate Interpretation of Process Dynamics

If you’re old enough to remember silent movies, then you know what it’s like to see the characters seemingly jiggle around the screen. Black spots would randomly appear as the story was told with the help of subtitles. Spots and subtitles aside, these movies appeared jittery due to their slow speed. The slow frame rate – a precursor of data collection speed – resulted in visual gaps.

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Using Percent Time in Normal to Uncover Tuning Issues

Even Simple Metrics Such as Percent Time in Normal Reveal Issues that Negatively Affect Performance and Signal the Need for Controller Tuning

It’s easy to get tripped up if a shoelace is untied. Just ask any child. While that’s a lesson most learn early in their lives each of us can occasionally slip up and find ourselves at risk.

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Using Mode Changes to Uncover Tuning Issues

Poor Controller Tuning.
Operator interventions and Mode Changes are often viewed negatively. When a PID loop is switched out of automatic there can be a sense that the controller wasn’t allowed to perform its job. With each change, goals related to production throughput and efficiency suffer a psychological hit. Since so much is invested in automating plant-wide production, interventions can feel like a step backwards. Viewed in a different light, however, those interventions provide potentially valuable insights that help production to move forward.

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Using the Oscillation Metric to Uncover Tuning Issues

There’s a wealth of information available in most every data historian. The data can be used to evaluate the performance of a plant’s regulatory control systems in general and to uncover PID controllers that require tuning in particular. Capitalizing on that resource can help manufacturers keep their processes within designated constraints and avoid out-of-spec production.

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What Is a Set Point Filter?

Names – like looks – can be deceiving. While jumbo shrimp are big relative to other shrimp there’s very little about them that could be considered gargantuan. So there should be no surprise to learn that in the realm of process control a Set Point Filter has nothing to do with filtering noise within a control loop’s data.

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