Use VT item suffixes

This section describes how a connected client requests access to items (or attributes) of a particular OPC data source. You can configure OPC and OPC UA data sources to use the /VT item suffix to gain better control of data access in Gateway Communication Driver. The /VT item suffix determines the type of data the underlying OPC server reports to the Gateway Communication Driver.

Note: When using a VT suffix, the suffix must be specified in the Item Reference column in the Device Items tab, not in the item name subscribed from a client.

To avoid delayed item validation, apply the /VT item suffix to an item name using the following syntax: <item name> /VT_<DataType>. For example, item1 /VT_I4.

Similarly, you can apply RequestVT (/VT item suffix) to an item name using the following syntax: /VT_<DataType>

For example, to specify a 2-byte signed Integer (/VT_I2) as the data type for an OPC UA server path of <OPCUAServer>.Blower.Int2, the item name in Gateway Communication Driver is subscribed as <OPCUAServer>.Blower.Int2 /VT_I2.

For information about specific VT data types, see OPC Data Conversion and OPC UA Data Conversion.