# System.opc.readValue/writeValue functionality question

**URL:** <https://forum.inductiveautomation.com/t/system-opc-readvalue-writevalue-functionality-question/84070>\
**Category:** Ignition\
**Created:** [January 10, 2024, 7:30pm UTC](https://forum.inductiveautomation.com/t/system-opc-readvalue-writevalue-functionality-question/84070 "2024-01-10T19:30:59Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![justin.huggins](https://avatars.discourse-cdn.com/v4/letter/j/d07c76/32.png) [@justin.huggins](https://forum.inductiveautomation.com/u/justin.huggins)\
**Post date:** [January 10, 2024, 7:30pm UTC](https://forum.inductiveautomation.com/t/system-opc-readvalue-writevalue-functionality-question/84070/1 "2024-01-10T19:30:59Z")

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I am trying to run a script using the OPC class within Ignition. When trying to read a value for the OPC item path I get 'Bad(Bad\_NodeIdUnknown....). Then I added this OPC item path to a OPC tag within Ignition. Once I do that, I can run the script and get good data as shown in the picture attached. Is this expected behavior, and if so does a way exist to do this in the script without having to create the dummy tag?

> path = 'ns=2;s=LAB\_ROC.98.1:24'  
> server = 'ACM\_04UA'
> 
> val = system.opc.readValue(server, path)  
> print(val)

 ![image](https://us1.discourse-cdn.com/inductiveautomation/original/3X/6/c/6cd9a763dffc74872fb6babe15efa2fa01d8a734.png)

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**Author:** ![Kevin.Herron](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/kevin.herron/32/7259_2.png) [@Kevin.Herron](https://forum.inductiveautomation.com/u/Kevin.Herron)\
**Post date:** [January 10, 2024, 7:39pm UTC](https://forum.inductiveautomation.com/t/system-opc-readvalue-writevalue-functionality-question/84070/2 "2024-01-10T19:39:05Z")

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No, not really expected. Seems like possibly a bug or lame implementation in the server you are connected to.

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<div class="post-metadata">

**Author:** ![justin.huggins](https://avatars.discourse-cdn.com/v4/letter/j/d07c76/32.png) [@justin.huggins](https://forum.inductiveautomation.com/u/justin.huggins)\
**Post date:** [January 10, 2024, 8:20pm UTC](https://forum.inductiveautomation.com/t/system-opc-readvalue-writevalue-functionality-question/84070/3 "2024-01-10T20:20:53Z")

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Autosol is working on a different bug fix for us in regards to OPC-UA. I can touch base to see if this might be related.