Reads the historical data for a given variable using the specified time interval, up to the max points per trace specified. You must manually select the polymorphic instance to use.

Use the pull-down menu to select an instance of this VI.


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Inputs/Outputs

  • ci32.png timeout (30 s) —

    timeout specifies the maximum time, in seconds, that this VI waits for reading data from the Citadel database. The default is 30. A timeout value of less than or equal to 0 specifies no timeout, which means this VI waits indefinitely until this VI receives data from the Citadel database.

  • ci32.png max points per trace (all) —

    max points per trace specifies the maximum number of points to read from the database. This VI returns all available points of this trace between start timestamp and stop timestamp in the following cases: max points per trace is less than zero. The number of the data points between start timestamp and stop timestamp is less than the max points per trace. If max points per trace is zero, this VI returns no point for the trace. The default is -1.

  • cpath.png database URL —

    database URL specifies the computer name and the database name where the Citadel database resides. Enter the database URL in the format \\computer\database.

  • cgenclassrntag.png trace name —

    trace name specifies the trace that this VI uses for the data operation. You can specify either a Shared Variable reference or an existing trace for this parameter. If the trace is not logged in the historical database, this VI returns an empty trace.

  • ccclst.png time interval —

    time interval is the span of time between the start timestamp and stop timestamp. If you do not wire this input, this VI reads all data logged up to now.

  • catrn.png start timestamp —

    start timestamp specifies the start date and time of data you want to retrieve from the Citadel database. If you do not wire this input, this VI uses the timestamp of the first data point in the database.

  • catrn.png stop timestamp (now) —

    stop timestamp specifies the end date and time of data you want to retrieve from the Citadel database. If you do not wire this input, this VI uses the timestamp of the last data point in the database.

  • cerrcodeclst.png error in (no error) —

    error in describes error conditions that occur before this node runs. This input provides standard error in functionality.

  • ccclst.png options —

    options specifies the format settings for the data as this VI reads the trace.

  • cbool.png —

    interpolate data? determines whether this VI estimates data values within an interpolation interval. The default is FALSE. If you set interpolate data? to TRUE, this VI estimates data values based on the data values that the DSC Module logs at the interpolation interval.

  • cbool.png —

    extrapolate to now determines whether this VI extrapolates the last data point in the database to the current system time. The default is FALSE. If you turn off logging for a shared variable, the DSC Module logs the last data point of this shared variable as a break. This VI does not extrapolate for traces that end with breaks unless you set remove data breaks? to TRUE.

  • cbool.png —

    remove data breaks determines whether to remove the value of a data break from the trace. The default is FALSE.

  • cdbl.png interpolation interval (1 s) —

    interpolation interval specifies the interval, in seconds, at which this VI interpolates the data. The default is 1.

  • cbool.png —

    maintain trending info determines whether to include the last data point before start timestamp and the first data point after stop timestamp with the returned trace. The default is TRUE. If this input is FALSE, the returned trace includes only points strictly between start timestamp and stop timestamp.

  • ipath.png database URL out —

    database URL out returns the computer name and the database name that specify where the Citadel database resides. The format is \\computer\database.

  • icclst.png historical trace —

    historical trace is the historical trace for the input trace name that is read from the historical database.

  • i1datrn.png timestamps —

    timestamps returns the timestamp of each value in the trace name array.

  • i1dstr.png data —

    data returns the data values of the data points.

  • i1di32.png quality —

    quality is the data quality of the trace(s) read. A value of zero indicates good quality.

  • ierrcodeclst.png error out —

    error out contains error information. This output provides standard error out functionality.

    • Read Trace Details

    If database URL is unwired, this VI reads the trace name from the database associated with the default DSC Module process.

    If you do not wire time interval, this VI returns all historical data for the trace, up to max points in trace specified. If you do not wire max points in trace, this VI returns all points between the start and stop timestamps set in time interval.

    Examples

    Refer to the NIHyperTrend Graph XML Configuration.lvproj in the labview\examples\lvdsc\HMI Design\NIHyperTrend Graph XML Configuration directory for an example of using the Read Trace VI.