CurrentValue is available on all advanced driver points and returns, not surprisingly, the current value of the point. Along with the CurrentValue property, there are a number of other properties that describe the current value of the point, such as:
- CurrentStateDesc - the current text description for the value of the point
- CurrentTime - the time the point was last updated
- CurrentValuerFormatted - the value as a string with the units appended
- and others...
The LoggedValue property is available on advanced driver points such as DNP3 points and specifies the last Logged data. Logged data is data where the reason for logging is a value change (a change which exceeded the significant change), state change, timed report or end of period. For a protocol such as DNP3, this means all event data is considered Logged data. Along with the value, it also allows for a number of other pieces of information about this value, such as:
- LoggedStateDesc - the text description for the value of the point
- LoggedTime - the time the logged data value changed
- LoggedValueFormatted - the logged value as a string with the units appended
- LoggedReason - the reason for the logged data.
The historic compression settings allow values in the database to not be written into the historic database unless they have changed by certain amounts or meet certain time criteria. In this case, the current values in the database (and all the associated properties) would be different to the logged values.
Similarly, some advanced drivers provide functionality to determine the types of data that are logged to the historic database, independent of the historic compression settings. In DNP3, it is possible to log either Static Data Only, Event Data Only or a combination of Static and Event Data. The Logged Data values will only be updated via time-stamped events being generated in the outstation and sent to ClearSCADA.