Configuring Variable Tags
- Last UpdatedFeb 06, 2025
- 3 minute read
Variable tags are addressed using the OPC UA NodeId configured in the OPC UA server.
NodeId consists of a namespace index and a unique identifier which can be a numeric value(i=), a string(s=), a globally unique identifier (g=), or an opaque value(b=).
Examples of NodeIds: "ns=2; i=12345" or "ns=3; s=SoftwareRevision"
Note: .The <Node ID> in a tag address cannot contain the following characters: "\", "!A"
and ";!E=".
"\" and "!A" characters are used for array tag addresses, and ";!E=" characters are
used for extension object tag addresses.
The following table demonstrates the variable tag address formats you can use to read and write values.
|
Address format |
OPC UA data type |
Plant SCADA data type |
Example |
|---|---|---|---|
|
<Node ID> |
BOOLEAN |
DIGITAL |
FALSE or TRUE |
|
<Node ID> |
SBYTE |
INT, LONG |
-128 to 127 |
|
<Node ID> |
BYTE |
INT, UINT, LONG, ULONG |
0 to 255 |
|
<Node ID> |
INT16 |
INT, LONG |
-32768 to 32767 |
|
<Node ID> |
UINT16 |
UINT, LONG, ULONG |
0 to 65535 |
|
<Node ID> |
INT32 |
LONG |
-2147483648 to +2147483647 |
|
<Node ID> |
UINT32 |
ULONG |
0 to 4294967295 |
|
<Node ID> |
INT64 |
<NOT SUPPORTED> |
|
|
<Node ID> |
UINT64 |
<NOT SUPPORTED> |
|
|
<Node ID> |
FLOAT |
REAL |
-3.4E38 to 3.4E38 |
|
<Node ID> |
DOUBLE |
REAL |
-3.4E38 to 3.4E38 |
|
<Node ID> |
STRING |
STRING |
ASCII string (0 to 254 characters) |
|
<Node ID> |
DATETIME |
STRING |
1990-01-01-00:00:00.000 to 2089-12-31-23:59:59.999 |
|
<Node ID> |
GUID |
<NOT SUPPORTED> |
|
|
<Node ID> |
XMLElement |
<NOT SUPPORTED> |
|
|
<Node ID> |
NodeId |
<NOT SUPPORTED> |
|
|
<Node ID> |
Expanded NodeId |
<NOT SUPPORTED> |
|
|
<Node ID> |
Qualified Name |
STRING |
Update the Qualified Name as string in the tag value |
|
<Node ID> |
Localized Text |
STRING |
Update the text in English Locale in the tag value |
|
<Node ID> |
Status Code |
LONG |
Update the Integer code in the tag value |
|
<Node ID> |
ByteString |
STRING |
Array of Bytes |
|
<Node ID> |
Enumeration |
LONG |
|
|
<Node ID> |
Variant |
<NOT SUPPORTED> |
|
|
<Node ID> |
Extension Object |
Plant SCADA data type corresponding to the Extension Object element data type. |
See the topic Extension Object Support. |
|
<Node ID> |
Number This is a Variant data type which can be FLOAT or DOUBLE. |
REAL Note: Only FLOAT OPC UA data type is supported, and the data type must not change on the server. |
|
|
<Node ID> |
Integer This is a Variant data type which can be SBYTE, INT16, INT32 or INT64. |
SBYTE: INT, LONG INT16: INT, LONG INT32: LONG Note: Only SBYTE, INT16 and INT32 OPC UA data types are supported, and the data type must not change on the server. |
|
|
<Node ID> |
UInteger This is a Variant data type which can be BYTE, UINT16, UINT32 or UINT64. |
BYTE: INT, UINT, LONG, ULONG UINT16: UINT, LONG, ULONG UINT32: ULONG Note: Only BYTE, UINT16 and UINT32 OPC UA data types are supported, and the data type must not change on the server. |
|
|
<Node ID> |
DiagnosticInfo |
<NOT SUPPORTED> |
The driver supports conversions between OPC UA data types and Plant SCADA data types. When a configured tag data type cannot be converted into OPC UA data type, the driver marks that tag with quality Bad, Configuration Error.
The following table shows supported conversions between Plant SCADA and OPC UA data types.
|
Plant SCADA data type |
OPC UA data type |
|---|---|
|
DIGITAL |
BOOLEAN |
|
INT, UINT |
SBYTE, BYTE, INT16, UINT16 |
|
LONG, UINT |
SBYTE, BYTE, INT16, UINT16, INT32,UINT32 |
|
REAL |
REAL |
|
STRING |
All OPCUA data types supported by the driver, except for BYTE, UINT16, UINT32, UINT64 |