Variable Types
OPC UA supports a number of data types for all sorts of cases. These variables are produced by one or more field devices such as sensors and actuators, then they are consumed by the OPC UA server. The OPC UA server then notifies subscribed OPC UA clients of these variables. The OPC UA clients then will consume all data produced by sensors and actuators through the OPC UA server.
Below, we have a table of current primitive variable types. Other variable types can be composed/derived from it.
| ID | Name | Nullable | Default | Description |
|---|---|---|---|---|
| 1 | Boolean | No | false | true or false |
| 2 | SByte | No | 0 | integer [−128, ..., 127] |
| 3 | Byte | No | 0 | integer [0, ..., 255] |
| 4 | Int16 | No | 0 | integer [−32,768, ..., 32,767] |
| 5 | UInt16 | No | 0 | integer [0, ..., 65,535] |
| 6 | Int32 | No | 0 | integer [−2,147,483,648, ..., 2,147,483,647] |
| 7 | UInt32 | No | 0 | integer [0, ..., 4,294,967,295] |
| 8 | Int64 | No | 0 | integer [−9,223,372,036,854,775,808, ..., 9,223,372,036,854,775,807] |
| 9 | UInt64 | No | 0 | integer [0, ..., 18,446,744,073,709,551,615] |
| 10 | Float | No | 0 | IEEE single precision floating point value (32 bit) |
| 11 | Double | No | 0 | IEEE double precision floating point value (64 bit) |
| 12 | String | Yes | null | sequence of Unicode characters |
| 13 | DateTime | Yes | DateTime.MinValue | An instance in time |
| 14 | Guid | Yes | All zeros | A 16-byte value that can be used as a globally unique identifier |
| 15 | ByteString | Yes | null | A sequence of octets |
| 16 | XmlElement | Yes | null | A sequence of Unicode characters that is an XML element |
| 17 | NodeId | Yes | All fields set to default | An identifier for a node in the address space of an OPC UA Server |
| 18 | ExpandedNodeId | Yes | All fields set to default | A NodeId that allows the namespace URI to be specified instead of an index |
| 19 | StatusCode | No | Good | A numeric identifier for an error or condition that is associated with a value or an operation |
| 20 | QualifiedName | Yes | All fields set to default | A name qualified by a namespace |
| 21 | LocalizedText | Yes | All fields set to default | Human readable text with an optional locale identifier |
| 22 | ExtensionObject | Yes | All fields set to default | A structure that contains an application specific data type that may not be recognized by the receiver |
| 23 | DataValue | Yes | All fields set to default | A data value with an associated status code and timestamps |
| 24 | Variant | Yes | Null | A union of all of the types specified above |
| 25 | DiagnosticInfo | Yes | No fields specified | A structure that contains detailed error and diagnostic information associated with a StatusCode |