# OPC UA Write This function block sends a value to an OPC UA server address using the provided client connection. Use it to update remote variables from your scenario with a selectable data type. ## đŸ“Ĩ Inputs `Client` OPC UA client instance to use for the write operation (typically provided by the `OPC UA Client` block) `Node Address` The target node address on the OPC UA server where the value will be written `Value` The value to send to the target node ## 📤 Outputs This function block does not provide outputs. ## 🕹ī¸ Controls `Data type` Dropdown to select the OPC UA variant type used when writing the value. Common selectable types include Float, Boolean, Integer variants, Double and String. ## 🎨 Features * Write with explicit data type selection so the target variable receives the expected type. * Works with an external OPC UA client instance to keep connectivity management separate. * Minimal UI: only requires the inputs and the data type selection for operation. ## ⚙ī¸ Running mechanism When the block is evaluated during a scenario run and the three inputs are provided, it will attempt to send the given `Value` to the specified `Node Address` using the supplied `Client` connection and the chosen `Data type`. Ensure the client is connected and the address is valid before running to avoid write failures. ## 📝 Usage instructions 1. Add and configure an `OPC UA Client` block to establish and manage the server connection. 2. Provide the client output into the `Client` input. 3. Set the target node address into the `Node Address` input. 4. Provide the data to write into the `Value` input. 5. Select the appropriate `Data type` from the dropdown that matches the server variable type. 6. Run the scenario or gate the write with a logic signal so writes happen only when desired. ## 💡 Tips and Tricks * Use the `OPC UA Client` block together with this block to manage connection lifecycle and reuse the same client for reads and writes. * Pair with the `OPC UA Read` block to verify current values before writing or to implement read-verify-write flows. * Use a `Logic Input` block to trigger writes only when a condition is met (for example, write on a button press or when a measurement exceeds a threshold). * Store or log values with `Data Write Global` / `Data Write Local` or export with `CSV Export` to keep an audit trail of writes. * When writing numeric values, prefer selecting the matching integer/float `Data type` to avoid type conversion errors on the server. ## 🛠ī¸ Troubleshooting * No client provided: make sure the `Client` input is connected (use the `OPC UA Client` block). * Connection errors: confirm the OPC UA client block shows a successful connection to the server before attempting writes. * Wrong address: verify the `Node Address` string is the exact address expected by the server. * Type mismatch: if the server rejects the value, try switching the `Data type` to the exact type of the target variable (e.g., Float vs Double, correct integer size). * Control unwanted writes: gate the input with a `Logic Input` or other logic blocks so writes only occur when intended. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.augelab.com/function-blocks/input-output/communication/opc-ua-write.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.