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Read OPC-UA History

Synopsis​

This operator reads historic data from a node that has the "history Read" property set, so it is storing past data values.

Description​

It is possible to specify a time window for which data should be collected. Additionally the amount of data points returned and the sampling frequency can be changed, which is useful if the data is collected at a high frequency with only small changes over time. Note that reading starts from the most recent values and then moves on to points further in the past.

Input​

connection​

Connection object specifying the connection to the OPC-UA server.

Output​

output​

ExampleSet that contains the historic data points and the time stamp at which they were collected.

Parameters​

Namespace id​

The ID of the namespace of the node from the where the browsing will start.

Node identifier​

The ID of the from the where the browsing will start. This only works for numeric node IDs.

Node id as string​

If selected the node identifier can be provided in the common OPC-UA format for example: "ns=0;i=1000". Possible options for the node identifier are: "i=" followed by a numeric identifier or "s=" followed by a string.

Start date for reading values​

Start date from when the data should be read.

End date for reading values​

Last date until data should be read. This date needs to be after (greater) the start date.

Number of values to read​

Absolut number of data points to be read. Reading begins at the start date and moves further until either the maximum number of values are read or the end date is reached. To make sure that all values in a time window are read, select a large enough number.

Read only every n-th value​

If checked, not all data values are returned, but only every n-th value. This is helpful if the data is collected at a high frequency, but the values only change gradually over time.

Selecting this option won't change the total number of data points returned. So for example if 100 data points should be read and only every tenth data point, the final example set will still contain 100 examples.

Size of interval to read values​

The number of data points to skip when collecting the historic data.