dOPCDA.TdOPCItem.ItemID

Identifier for OPC items

Delphi

property ItemID: string;

C++

__property AnsiString ItemID;

Description

To identify OPC Items the TdOPCDAClient works with unique ItemIds. The ItemId is a string.

Here an example how to add an ItemId to a OPC group:

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G.OPCItems.AddItem('Random.String');

In OPC UA, every entity in the address space is a unique node.

Each node has a NodeId object, which is has 3 properties:

Property
NamespaceIndex	The namespace index as a number. Default is 0.
IdentifierType	The data type of the identifier. Default is string
Identifier	The identifier for a node.

Following Identifier types are supported:

IdentifierType	character
number	i
string	s
globally unique identifier (GUID)	g
opaque value (ByteString)	b

To convert a NodeId object to a string based ItemId you have to use following format:

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ItemId := ns=<NamespaceIndex>;<Identifiertype>=<Identifier>

Examples:

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  G.OPCItems.AddItem('ns=0;i=2256');    // NodeId with IdentifierType i = number and NamespaceIndex = 0
  G.OPCItems.AddItem('ns=5;s=Random1'); // NodeId with IdentifierType s = string  and NamespaceIndex = 5

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