The trend extension monitors and records the changes in the behavior of an individual attribute over time, thereby assisting you with diagnosing various system-wide behavioral characteristics. The trend extension collects sample values at timed intervals or only upon changes in the given value. Trend data is still collected if the object is unreliable. The trend extension continues to log data using the previous value preceded by ???, which indicates an unreliable status.
For example, use a trend extension to collect data from the Analog Input object of a controller on the N2 Bus, which reports information such as outdoor air temperature or room air temperature.
Trend extensions are different from Trend Studies because Trend Studies query both the ADS and Network Engine for historical data. Trend extensions query only the Network Engine.
For trend performance information, refer to the Metasys System Configuration Guide (LIT-12011832).