Video: Characterization Function for Implementing Ratio Control

By Cecil Smith, president of Cecil L. Smith, Inc.

The control configuration proposed in the previous video included a characterization function whose purpose can be stated as follows: Given a value for the fuel gas valve opening, determine the fresh air damper opening required to give a hot air temperature of 210°C. The focus of this video is obtaining data points for this characterization function.

To access the entire video series from Cecil Smith, visit our video page.

Cecil Smith is president of Cecil L. Smith, Inc., Houston, a firm specializing in automation technology that he founded after leaving the faculty of Louisiana State University. Also cited as one of the 50 most influential people in the field, he teaches courses on control topics and has authored or co-authored 14 books, including “Digital Control of Industrial Processes and more than 100 articles. You can email him at He is also one of our experts in our Ask the Experts forum. You can pose your instrumentation and control questions to him here.