History Data Multiple Read VI

Owning Palette: Historical Access VIs

Requires: OPC UA Toolkit

Reads history data for one or multiple nodes.

Example

	continuation points in specifies the continuation point and whether the history data has a continuation point. continuation point specifies the point from which this VI continues to read if the OPC UA server cannot return all values in one response. has continuation point? specifies whether the history data has a continuation point. The default is TRUE, which specifies that the history data has a continuation point.
	OPC UA client refnum in specifies the reference for the OPC UA client.
	node IDs specifies the IDs of the nodes. The format of the node ID is ns=<namespace index>;<identifier type>=<identifier>. A node ID contains the following components: namespace index is a base 10 number that indicates the namespace of the node ID. If namespace index is 0, the format of the node ID can be <identifier type>=<identifier>. The namespace index for a node that you created with the OPC UA Toolkit is 2. identifier type represents the type of the identifier and has the following values: Value Identifier Type i Numeric s String g GUID b Opaque identifier is a string value that represents the name of the identifier. The format of the node ID can also be ns=<namespace index>;<identifier type>=<identifier>@<index>:<index>. For example, ns=2;s=Folder.Array@1:2. This format only applies to the array data type and allows you to read a single element or a range of elements of an array. You cannot use @ in a node name. For backwards compatibility, node IDs also accepts node paths as input for OPC UA servers only. You can regard the node path as the string type identifier of the node ID. For example, a node path can be Device.folder.item.
	request specifies the start time, the end time, the maximum number of values to return over the time range, and whether to return bounding values. start time specifies the timestamp at which this VI reads the first history data. end time specifies the timestamp at which this VI reads the last history data. num values per node specifies the maximum number of values to return over the time range. The default is 0, which specifies that this VI returns all values over the time range. return bounds specifies whether to return bounding values. The default is FALSE, which specifies that this VI does not return bounding values. Bounding values are values associated with the starting time and the ending time. An OPC UA client can require bounding values to determine the starting and ending values when requesting data over a time range.
	error in describes error conditions that occur before this node runs. This input provides standard error in functionality.
	timeout specifies the maximum time that this VI waits to get a response from the OPC UA Server. The default value is 5000.
	OPC UA client refnum out returns the reference for the OPC UA client.
	results returns the IDs of the nodes, the history data, and the statuses of the nodes. node ID returns the ID of the node. history data returns history data that this VI reads. value returns the history data. timestamp returns the timestamp at which data is generated. node status returns the status of the node. status returns the status code.
	continuation points out returns the continuation point and whether the history data has a continuation point. continuation point returns the point from which this VI continues reading if the OPC UA server cannot return all values in one response. has continuation point? returns whether the history data has a continuation point.
	error out contains error information. This output provides standard error out functionality.
	service status returns the status of an OPC UA service call. OPC UA services contain parameters that are conveyed between an OPC UA client and an OPC UA server.

Example

Refer to the OPC UA Demo.lvproj in the labview\examples\Data Communication\OPCUA directory for an example of using the History Data Multiple Read VI.