Use the fields within the Significant Change section of the tab to define the amount by which a counter point’s value has to change before it is reported to the ClearSCADA server.
Use the Significant Change feature to help prevent excessive database updates. It allows you to define whether a counter point’s value change is stored in the database or is deemed as insignificant and is discarded. If ClearSCADA discards a value, the counter point’s previous recorded value is retained in the ClearSCADA database.
Configure the required settings using these fields within the Significant Change section of the tab:
- Type—Use this combo box to define the type of significant change. Choose from:
- None—The server only updates the point value in the ClearSCADA database when one or more of the following occurs:
- The point changes state
- The point’s Scan Group interval expires
- A user requests a Refresh of a display on which the point is included
- On system or driver start-up.
- Absolute—In addition to the reasons listed in ‘None’ above, the point value will be updated in the ClearSCADA database if it changes by a defined amount. You can define the amount by which the value has to change in the Deadband field.
- None—The server only updates the point value in the ClearSCADA database when one or more of the following occurs:
- Deadband—Enter the amount by which the point value has to change for it to be deemed significant.
Example:
A counter point is scanned every 5 seconds and reports a value of 10. There is no need for the database to log the same value every 5 seconds. Significant Change is used to only log the value when it changes by more than 2 (Type = Absolute, Deadband = 2). The point’s value is only updated in the ClearSCADA database when it reaches or rises above 12, and thereafter whenever the value increases by 2 or more.
- Log Event—Select this check box for any significant changes in point value to be logged in the Event Journal.
ATTENTION: Numerous messages may be logged in the Event Journal if Log Event is enabled for a point that frequently changes significantly in value.
Ensure that the Log Event check box is clear if any significant changes in point value are to be updated in the database, but not logged in the Event Journal.