Displaying Trends (DSC Module)
August 2006
NI Part Number:
370246E-01
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A trend is a graph display of shared variable values over time. With the DSC Module, you have several options for displaying trends for real-time and historical data.
Displaying Real-Time Trends
A real-time trend is a display of shared variable values as they are collected in real time over a relatively short period of time. You can use the Real-Time Trend Express VI to display a real-time trend in an application.
Because the Real-Time Trend Express VI waits the specified time interval, place the VI in its own While Loop to control the execution rate of the Real-Time Trend Express VI. To run other VIs at the same rate that the real-time trend updates, place them in the same While Loop.
The Real-Time Trend Express VI updates the value for each shared variable every time the Shared Variable Engine writes to the waveform chart output of the VI. If a VI using this indicator runs several times, the real-time trend continues to display previously acquired data. You might want to initialize the Real-Time Trend Express VI before the While Loop begins executing.
Displaying Historical Trends
A historical trend is a display of project values that have been logged to the Citadel historical database, usually over a relatively long period of time. If you configure an application to log values, you can display a historical trend in several ways.