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We all intuitively know that in any setting, some information is more important than other information. The problem arises in how to convey the greater importance of certain data to system users. The problem is increased in most process control plants due to the large amount of data that an operator must examine.

Dr. William A. Simcox investigated a method of weighing information presented in graphic displays, "A Method for Pragmatic Communication in Graphic Displays," Human Factors, 1984, 26(4), 483-487. In looking at the slopes of bar and line charts, Dr. Simcox discovered that certain slopes gave the reader a connotation or feeling of a slightly increasing trend while other slopes with the same data gave a connotation of a sharply increasing trend.

This indicates that if it is essential to warn an operator of a changing parameter, then a display with a slope which "means" or gives the feeling of a rapidly changing condition should be utilized. Likewise, for those variables for which over reaction on the part of the operator is not desired, a slope providing a "slightly increasing" connotation should be utilized. Specific equations were developed that generate the slopes to achieve the various meanings.

Copyright 1985 Beville Engineering, Inc. , All Rights Reserved

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