The LabVIEW Datalogging and Supervisory Control (DSC) Module provides OPC Client I/O servers for communicating with any server implementing the OPC Foundation OPC server interface, which is a Microsoft COM-based standard. An OPC Client I/O server lists all OPC servers installed on the computer and reads any available information about the server capabilities and items directly from the server. You can create an OPC Client I/O server to access data items on a local or remote OPC server. You also can configure a local OPC server to work with an OPC Client I/O server.
Additionally, you can use I/O servers to connect to the NI OPC Servers that the DSC Module provides. Use the NI OPC Servers application, available by selecting Start»All Programs»National Instruments»NI OPC Servers»NI OPC Servers, to transfer data from industrial devices and systems to client applications on a host computer. The NI OPC Servers application enables data sharing between a variety of applications, such as Human Machine Interface (HMI) software, manufacturing execution systems, and enterprise resource planning applications.
|Note By default, the NI OPC Servers application is installed when you install the DSC Module. You have a temporary license for a two-hour evaluation period. If you do not activate the NI OPC Servers application license, this application runs in evaluation mode for two hours. When the evaluation period expires, you must activate a valid license to continue using the NI OPC Servers application. Refer to the NI OPC Servers Help, available by selecting Start»All Programs»National Instruments»NI OPC Servers»NI OPC Servers Help, for more information about activating and using the NI OPC Servers application.|
You must verify the DCOM configuration for a local OPC server before you connect an OPC Client I/O server to the OPC server. National Instruments recommends that you configure the OPC server to run with an identity of The interactive user.
You can use an OPC Client I/O server to access OPC servers running on other computers on the network. An OPC Client I/O server enables you to access different instances of the same remote OPC server.
Logging diagnostic information about OPC Client I/O servers can help you debug an OPC system. You can use the options on the Diagnostics page of the Configure OPC Client I/O Server dialog box to log diagnostic information about the OPC Client I/O servers you create.
OPC Client I/O servers communicate with both LabVIEW and the Shared Variable Engine (SVE) and log this communication to HTML log files. The HTML file you specify in the Log file option logs the communication between the SVE and the OPC Client I/O server you create. OPC Client I/O servers generate separate log files to log the communication between LabVIEW and the OPC Client I/O servers. For example, if you specify a log file named logfile.html, the OPC Client I/O server automatically generates a logfile_LV.html file to log the communication between LabVIEW and the OPC Client I/O server. The log files highlight communication activities in blue and communication errors in red. The log files also provide explanations of the communication errors. You can use the log files to debug an OPC system.