You can define one or more delta EU triggers that initiate an acquisition when a feature or spectral band changes by at least a specified amount. Both positive and negative changes in value cause a delta EU trigger to fire.
This setting can be found on the Operating States Tab of the Asset Configuration page.
The following process explains how the InsightCM Server monitors delta EU triggers.
|When a device starts running, it sets the current value of the feature or spectral band as the baseline EU value.||Consider a feature whose value is 1 upon startup. The baseline EU value is therefore 1.|
|The device monitors the feature value regularly and compares it to the baseline value to check for a difference greater than the trigger level.||Consider a delta EU trigger with a delta level of 3. Given the baseline EU value of 1, the device checks for values less than -2 and greater than 4 to see if the trigger condition is met.|
|If the current value increases or decreases by the delta level, the trigger fires and the devices performs an acquisition.||If the current value is 8, the device performs one acquisition.|
|The device sets the value that caused the trigger to fire as the new baseline value.||The new baseline EU value is 8.|
|The device continues to calculate the feature value to see if the difference from the baseline is greater than the delta level.||Given the new baseline of 8, the device checks for values less than 5 and greater than 11.|
Only the initial start-up value and values that cause delta EU triggers to fire can serve as the baseline EU value. In other words, when a device performs a time-, alarm-, or force-triggered acquisition, the device does not update the baseline EU value with the feature value from that acquisition.