Concept
Change of Value Trend Logs
The change of value trend log records the variable each time the difference between the current value and the last log value exceeds the delta. Use the change of value trend log to, for example, record a variable that has an unequal oscillation.
The change of value trend log is limited to 10 records per second.
Do not set the delta too small since this can quickly fill up the trend log.
For example, in the figure below, the change of value trend log records a variable every time the variable exceeds or falls below the delta of 3. The records are printed in a trend chart. Notice that the change of value trend log records the values without any time perspective between the records.
Change of value trend log schematic.
The change of value trend log, which is not a variable triggered trend log, has the function to start log records according to a given start condition. For more information, see Trend Log Activation .
You can configure the maximum log interval in a change of value trend log. The maximum log interval is the maximum time that can elapse between two recordings regardless of whether the value has changed or not. The maximum log interval is calculated from the last actual recording. When the maximum log interval is configured, it bypasses the delta and the recording is triggered when the configured time period has elapsed.
Trend Log Types
Trends Overview
Trend Units
Creating a Change of Value Trend Log
Configuring a Change of Value Trend Log
Change of Value Trend Log Properties