Access to historical data
You can use any OPC UA client that supports the OPC UA Historical Access function to get historical data. In the following example, the "UA Expert" software from Unified Automation is used to read historical data from the TwinCAT OPC UA Server and display it visually.
Displaying Historical Access values in an OPC UA client
The following step-by-step instructions describe how to configure the UA Expert software in order to access historical data.
- 1. Start the UA Expert software and connect to the OPC UA Server.
- 2. Add a new History Trend View.
- 3. Browse the PLC1 namespace and use drag & drop to add the PLC variables _HistoryDB, _HistoryDBcompact, _HistoryFast and _HistorySlowPersist.
- You can now use the Start Time and End Time controls to specify the desired time period for which the symbol values are to be displayed, or you can start a Cyclic Update for these variables if necessary.
