Design Pattern: RF(4) Trend displays


A set of incoming alarms has been registered. After getting an overview of the status of the controlled process, the human operator would like to access to a more detailed information. In particular, he would like to compare and understand the evolution alarms across different dimensions such as priority, typology or time in order to avoid possible occurrences and deviations in the controlled process.


The human operator needs to visualize the activity of alarms across different dimensions in order to project future states of the controlled process.


Use trend displays to show the time history of alarms. Trend displays should be displayed with sufficient resolution in time and magnitude to ensure that rapidly changing variables can be observed and accurately interpreted. The time history should cover enough time and be accurate enough to depict the onset and development of conditions that vary from preceding normal operating conditions. [19][140]. Trend displays should convey also enough information to allow the operator to interpret the data without referring to additional sources. They should form recognizable geometric patterns for specific abnormal conditions. A short time base of just a few minutes is needed to study fast changing trends, while other trends may not show significant changes for several hours.

Known uses
Fig1. Trend display showing changes in a parameter over time
Fig2.DIASYS control system provides a trend display showing the operation status of facilities, and failure alarms in a power grid

Trend displays allow operators to make decisions about the performance of a variable or variables over time (Endsley, M. R. (2003). Designing for situation awareness: An approach to user-centered design CRC Press.)