Monthly Archive: December 2010

Dec
30

Universal Concept – Deadtime

The most important parameter for process control is the easiest to identify. The time after a change in the PID output till you see a significant change in the process variable is the total loop deadtime. Deadtime is directly or indirectly a factor in all aspects of control system design and tuning for loop performance. …

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Dec
27

Process Characterization – Inverse Process Response

Process characterization is the identification of the dynamic responses of a process to changes in its inputs. As part of the chapter on process characterization in Chapter 9 of Control Loop Foundation, we address inverse process response. A few processes exhibit a behavior where for a step change in input, the output initially changes in …

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Dec
23

XY Plots for Operations and Process Analysis

Process visualization and interaction for operations are about to enter the 21st century after being stuck in the 1980s. Emerson and major companies in the process industries and universities through organizations such as the Center for Operator Performance are doing research on how to increase the effectiveness of operators to match the increased capability of …

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Dec
22

Temperature Measurement – The Most Important of the Common Measurements

Temperature is often the key measurement for composition, product quality, and energy use. Today’s temperature measurements are now capable of an accuracy and precision commensurate with the control capability of a well tuned loop. For more details see the Dec 16 post “Star Performers for Minimizing Life Cycle Costs” updated with the links to pertinent …

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Dec
20

Process Characterization – Self-regulating Process

Process characterization is the identification of the dynamic responses of a process to changes in its inputs. In Chapter 9 of Control Loop Foundation, we address process characterization. In some cases the process response may be characterized as a pure gain, lag, or deatime. However, many of the basic thermal and physical mechanisms reflected in …

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Dec
16

Star Performers in Minimizing Life Cycle Costs

Projects tend to focus on purchase price of the control and automation system even though it is a small fraction of the total life cycle cost, which in my book includes the cost of implementation, maintenance, and any adverse effects on process variability. Hunter Vegas’s #1 “Piece of Advice” in The Final Word on Instrument …

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Dec
13

Tutorial Series – Foundation Fieldbus

As noted in a previous post, when work on Foundation Fieldbus specification was completed in 1994, there were very few fieldbus products on the market and even fewer control systems that supported these devices. The Fieldbus Foundation function block team discussed the need to communicate the advantages of fieldbus to inform the industry of this …

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Dec
09

Measurement and Valve Errors – Sources and Impact

For purposes of analysis of the impact on industrial process control, the sources of a PID input error (deviation between the true process variable and the measurement signal) and a PID output error (deviation between valve-VFD signal and actual stroke-speed) are (Measurement-Valve-Errors.pdf): (1) Offset (2) Drift (3) Nonlinearity (4) Interference (5) Noise (6) Hysteresis (7) …

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Dec
08

Exceptional Opportunities in Process Control Course Presentations

The ISA course in Saint Louis went well. Emerson donated my time for this educational opportunity to provide a “hands-on-learning” experience that supports our technical society as automation engineers. Students really appreciated the process control labs, particularly the ones using the auto tuner and the PID enhanced for wireless (PIDPlus). The presentations for the 3-day …

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Dec
06

Roundtable Presentation – Life Science Industry Forum

The Food and Drug Administration issued the guideline “Guidance for Industry, PAT — A Framework for Innovative Pharmaceutical Development, Manufacturing, and Quality Assurance” in September, 2004. The objective of this guidance was to “describe a regulatory framework (Process Analytical Technology, PAT) that will encourage the voluntary development and implementation of innovative pharmaceutical development, manufacturing, and …

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