Read Traces VI
- Updated2023-02-21
- 24 minute(s) read
Read Traces VI
Owning Palette: Historical VIs
Requires: DSC Module
Reads the historical data for a group of traces using the specified time interval, up to the max points per trace specified.
You must manually select the polymorphic instance to use.
Read Traces (Numeric)
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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. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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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:
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database URL specifies the computer name and the database name where the Citadel database resides. Enter the database URL in the format \\computer\database. For example, if you have a copy of the LabVIEW Datalogging and Supervisory Control (DSC) Module and Citadel service installed on a computer named datalogger and the name of the database on that computer is data, you can access the data on datalogger from another computer by using the path \\datalogger\data. If you provide a database name only, this VI searches for the database on the local computer. If you do not wire database URL, this VI resolves the database URL from the Shared Variable Engine (SVE). If the SVE resolution fails, this VI reads data from the database associated with the default DSC Module process. |
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trace names specifies the list of historical traces for which you want to read historical data. You can specify either Shared Variable references or existing traces for this parameter. The DSC Module uses these trace names as column headers when you convert this information into spreadsheet format. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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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.
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error in describes error conditions that occur before this node runs. This input provides standard error in functionality. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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options specifies the format settings for the data as this VI reads the traces.
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database URL out returns the computer name and the database name that specify where the Citadel database resides. The format is \\computer\database. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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historical traces is the trace data for each input trace name read from the historical database, starting at the date and time specified by start timestamp and stopping at the date and time specified by stop timestamp or up to max points per trace, whichever is smaller. If the start timestamp and stop timestamp values are unwired, all the logged data up to max points per trace for the trace is returned. If a value is a data break, this output returns a data point whose data is NaN and whose timestamp you can ignore.
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quality is the data quality of the trace(s) read. A value of zero indicates good quality. The following table lists some of the possible quality values.
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error out contains error information. This output provides standard error out functionality. |
Read Traces (Bit Array)
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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. | ||||||||||
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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:
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database URL specifies the computer name and the database name where the Citadel database resides. Enter the database URL in the format \\computer\database. For example, if you have a copy of the LabVIEW Datalogging and Supervisory Control (DSC) Module and Citadel service installed on a computer named datalogger and the name of the database on that computer is data, you can access the data on datalogger from another computer by using the path \\datalogger\data. If you provide a database name only, this VI searches for the database on the local computer. If you do not wire database URL, this VI resolves the database URL from the Shared Variable Engine (SVE). If the SVE resolution fails, this VI reads data from the database associated with the default DSC Module process. |
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trace names specifies the list of historical traces for which you want to read historical data. You can specify either Shared Variable references or existing traces for this parameter. The DSC Module uses these trace names as column headers when you convert this information into spreadsheet format. | ||||||||||
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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.
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error in describes error conditions that occur before this node runs. This input provides standard error in functionality. | ||||||||||
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options specifies the format settings for the data as this VI reads the traces.
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database URL out returns the computer name and the database name that specify where the Citadel database resides. The format is \\computer\database. | ||||||||||
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historical traces is the trace data for each input trace name read from the historical database, starting at the date and time specified by start timestamp and stopping at the date and time specified by stop timestamp or up to max points per trace, whichever is smaller. If the start timestamp and stop timestamp values are unwired, all the logged data up to max points per trace for the trace is returned. If a value is a data break, this output returns a data point whose data is NaN and whose timestamp you can ignore.
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quality is the data quality of the trace(s) read. A value of zero indicates good quality. | ||||||||||
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error out contains error information. This output provides standard error out functionality. |
Read Traces (Logical)
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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. | ||||||||||
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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:
|
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database URL specifies the computer name and the database name where the Citadel database resides. Enter the database URL in the format \\computer\database. For example, if you have a copy of the LabVIEW Datalogging and Supervisory Control (DSC) Module and Citadel service installed on a computer named datalogger and the name of the database on that computer is data, you can access the data on datalogger from another computer by using the path \\datalogger\data. If you provide a database name only, this VI searches for the database on the local computer. If you do not wire database URL, this VI resolves the database URL from the Shared Variable Engine (SVE). If the SVE resolution fails, this VI reads data from the database associated with the default DSC Module process. |
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trace names specifies the list of historical traces for which you want to read historical data. You can specify either Shared Variable references or existing traces for this parameter. The DSC Module uses these trace names as column headers when you convert this information into spreadsheet format. | ||||||||||
![]() |
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.
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error in describes error conditions that occur before this node runs. This input provides standard error in functionality. | ||||||||||
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options specifies the format settings for the data as this VI reads the traces.
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database URL out returns the computer name and the database name that specify where the Citadel database resides. The format is \\computer\database. | ||||||||||
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historical traces is the trace data for each input trace name read from the historical database, starting at the date and time specified by start timestamp and stopping at the date and time specified by stop timestamp or up to max points per trace, whichever is smaller. If the start timestamp and stop timestamp values are unwired, all the logged data up to max points per trace for the trace is returned. If a value is a data break, this output returns a data point whose data is NaN and whose timestamp you can ignore.
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quality is the data quality of the trace(s) read. A value of zero indicates good quality. | ||||||||||
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error out contains error information. This output provides standard error out functionality. |
Read Traces (String)
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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. | ||||||||||
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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:
|
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![]() |
database URL specifies the computer name and the database name where the Citadel database resides. Enter the database URL in the format \\computer\database. For example, if you have a copy of the LabVIEW Datalogging and Supervisory Control (DSC) Module and Citadel service installed on a computer named datalogger and the name of the database on that computer is data, you can access the data on datalogger from another computer by using the path \\datalogger\data. If you provide a database name only, this VI searches for the database on the local computer. If you do not wire database URL, this VI resolves the database URL from the Shared Variable Engine (SVE). If the SVE resolution fails, this VI reads data from the database associated with the default DSC Module process. |
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trace names specifies the list of historical traces for which you want to read historical data. You can specify either Shared Variable references or existing traces for this parameter. The DSC Module uses these trace names as column headers when you convert this information into spreadsheet format. | ||||||||||
![]() |
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.
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![]() |
error in describes error conditions that occur before this node runs. This input provides standard error in functionality. | ||||||||||
![]() |
options specifies the format settings for the data as this VI reads the traces.
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database URL out returns the computer name and the database name that specify where the Citadel database resides. The format is \\computer\database. | ||||||||||
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historical traces is the trace data for each input trace name read from the historical database, starting at the date and time specified by start timestamp and stopping at the date and time specified by stop timestamp or up to max points per trace, whichever is smaller. If the start timestamp and stop timestamp values are unwired, all the logged data up to max points per trace for the trace is returned. If a value is a data break, this output returns a data point whose data is NaN and whose timestamp you can ignore.
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quality is the data quality of the trace(s) read. A value of zero indicates good quality. | ||||||||||
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error out contains error information. This output provides standard error out functionality. |
Read Traces (Variant)
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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. | ||||||||||
![]() |
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:
|
||||||||||
![]() |
database URL specifies the computer name and the database name where the Citadel database resides. Enter the database URL in the format \\computer\database. For example, if you have a copy of the LabVIEW Datalogging and Supervisory Control (DSC) Module and Citadel service installed on a computer named datalogger and the name of the database on that computer is data, you can access the data on datalogger from another computer by using the path \\datalogger\data. If you provide a database name only, this VI searches for the database on the local computer. If you do not wire database URL, this VI resolves the database URL from the Shared Variable Engine (SVE). If the SVE resolution fails, this VI reads data from the database associated with the default DSC Module process. |
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![]() |
trace names specifies the list of historical traces for which you want to read historical data. You can specify either Shared Variable references or existing traces for this parameter. The DSC Module uses these trace names as column headers when you convert this information into spreadsheet format. | ||||||||||
![]() |
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.
| ||||||||||
![]() |
error in describes error conditions that occur before this node runs. This input provides standard error in functionality. | ||||||||||
![]() |
options specifies the format settings for the data as this VI reads the traces.
| ||||||||||
![]() |
database URL out returns the computer name and the database name that specify where the Citadel database resides. The format is \\computer\database. | ||||||||||
![]() |
historical traces is the trace data for each input trace name read from the historical database, starting at the date and time specified by start timestamp and stopping at the date and time specified by stop timestamp or up to max points per trace, whichever is smaller. If you do not wire the start timestamp and stop timestamp values, this VI returns all the logged data up to max points per trace for the traces. If a value is a data break, this output returns a data point whose data is NaN and whose timestamp you can ignore.
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quality is the data quality of the trace(s) read. A value of zero indicates good quality. | ||||||||||
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error out contains error information. This output provides standard error out functionality. |
Read Traces Details
If you do not wire database URL, this VI reads data 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 traces, up to the max points per trace specified. If you do not wire max points per trace, this VI returns all points between the start and stop timestamps set in time interval. If you do not wire interpolate data, the DSC Module preserves gaps in the data as invalid (NaN) values. If you set interpolate data to TRUE, the DSC Module ignores the gaps, and the trace interpolates across the gap in the data.
Example
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 Traces VI.