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This function is used in Python Scripting.

Description

Reads a single value directly from an OPC server connection. The address is specified as a string, for example, [MyDevice]N11/N11:0. The object returned from this function has three attributes: valuequality, and timestamp. The value attribute represents the current value for the address specified.

The quality attribute is an OPC UA status code. You can easily check a good quality vs a bad quality by calling the isGood()function on the quality object. The timestamp attribute is Date object that represents the time that the value was retrieved at.

Client Permission Restrictions

This scripting function has no Client Permission restrictions.

Syntax

system.opc.readValue(opcServer, itemPath)

  • Parameters

String opcServer - The name of the OPC server connection in which the item resides.

String itemPath - The item path, or address, to read from.

  • Returns

QualifiedValue - QualifedValue object that contains the value, quality, and timestamp returned from the OPC server for the address specified.

  • Scope

Gateway, Vision Client, Perspective Session

Code Examples
Code Snippet
server = "Ignition OPC UA Server"
path = "[SLCSim]_Meta:N7/N7:0"
qualifiedValue = system.opc.readValue(server, path)
print "Value: " + str(qualifiedValue.getValue())
print "Quality: " + qualifiedValue.getQuality().toString()
print "Timestamp: " + qualifiedValue.getTimestamp().toString()
Keywords

system opc isServerEnabled, opc.isServerEnabled