Author Archive | Greg McMillan

PID-Tuning-Rules

PID Tuning Rules

Nearly every automation system supplier, consultant, control theory professor, and user has a favorite set of PID tuning rules. Many of these experts are convinced their set is the best. A handbook devoted to tuning has over 500 pages of rules. The enthusiasm and sheer number of rules is a testament to the importance of […]

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vessel-control-loops-need-reset-time-increased-by-two-or-more-orders-of-magnitude-slider

How to Avoid Common Tuning Mistakes

The proportional, integral, derivative (PID) controller is the common key component of all control loops. Basic control systems depend upon the PID to translate the measurement signals into set points of secondary loop controllers, digital valve controllers, and speed controllers for variable frequency drives. The success of advanced control, such as model predictive control, depends […]

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industrial-applications-thermal-mass-flowmeters

The Good, Bad and Ugly of Thermal Mass Flowmeters

Thermal mass flowmeters can be a relatively inexpensive flowmeter that can handle extremely small flows (e.g., inline 1/16-inch meters) and large flows (e.g., multipoint insertion type in 60 inch ducts). Thermal flowmeters introduce heat into the flow stream and measure how much heat is absorbed using one or more temperature sensors. However, the meter requires […]

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near-integrating-process-response

PID Tuning for Near and True Integrating Processes

The most important loops on vessels and columns typically have a near or true integrating response. A self-regulating process is classified as near integrating if the process time constant is larger than four times the process dead time. The composition, pH, and temperature response of continuous columns tend to have a time constant to dead […]

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How Do You Measure Control System Performance?

For the automation profession to gain the recognition it deserves, we need to show the impact of our achievements on improving plant performance. This question is from Sridhar Dasani, a recent addition to the ISA Mentor Program, with my answer and additional input from co-founder of the program Hunter Vegas (project engineering manager at Wunderlich-Malec) […]

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