# Issue to Expression tag in Iginition 8.1

**URL:** <https://forum.inductiveautomation.com/t/issue-to-expression-tag-in-iginition-8-1/67730>\
**Category:** Ignition\
**Tags:** ignition81, perspective\
**Created:** [December 16, 2022, 7:21pm UTC](https://forum.inductiveautomation.com/t/issue-to-expression-tag-in-iginition-8-1/67730 "2022-12-16T19:21:46Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![Leandro\_Garcia\_Carva](https://avatars.discourse-cdn.com/v4/letter/l/6f9a4e/32.png) [@Leandro\_Garcia\_Carva](https://forum.inductiveautomation.com/u/Leandro_Garcia_Carva)\
**Post date:** [December 16, 2022, 7:21pm UTC](https://forum.inductiveautomation.com/t/issue-to-expression-tag-in-iginition-8-1/67730/1 "2022-12-16T19:21:46Z")

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Hi,

This is my expression tag that was workin in 7.8.

 ![image](https://us1.discourse-cdn.com/inductiveautomation/original/3X/6/b/6b7590491a54eeb214d505bca9afebd8d933933f.png)  
Now it doesn`t works in 8.1.  
The fault bellow comes up  
 ![image](https://us1.discourse-cdn.com/inductiveautomation/original/3X/9/9/996989a25741a0b161c4f61c076472bdffa99c06.png)

How can I figure it out?  
Please check the tags below:  
[image|690x166](https://forum.inductiveautomation.com/uploads/short-url/tQR3smyFWdFQUlanPhyOn0xokmj.png)

 ![image](https://us1.discourse-cdn.com/inductiveautomation/original/3X/9/4/94d8364b9f7894242b221574677ac27ab65f530d.png)  
Read and right was enabled to all tags.

Regards,

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<div class="post-metadata">

**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:** [December 16, 2022, 7:23pm UTC](https://forum.inductiveautomation.com/t/issue-to-expression-tag-in-iginition-8-1/67730/2 "2022-12-16T19:23:47Z")

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What doesn't work? When does that error message appear? It seems to be in response to something attempting to write to the expression tag, which is not and has never been allowed.

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**Author:** ![kcollins](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/kcollins/32/19646_2.png) [@kcollins](https://forum.inductiveautomation.com/u/kcollins)\
**Post date:** [December 16, 2022, 7:41pm UTC](https://forum.inductiveautomation.com/t/issue-to-expression-tag-in-iginition-8-1/67730/3 "2022-12-16T19:41:23Z")

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My guess is that trying to write to that expression tag probably just didn't produce the error dialog (in 7.8.x) you're now rightfully getting.

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<div class="post-metadata">

**Author:** ![Leandro\_Garcia\_Carva](https://avatars.discourse-cdn.com/v4/letter/l/6f9a4e/32.png) [@Leandro\_Garcia\_Carva](https://forum.inductiveautomation.com/u/Leandro_Garcia_Carva)\
**Post date:** [December 16, 2022, 8:01pm UTC](https://forum.inductiveautomation.com/t/issue-to-expression-tag-in-iginition-8-1/67730/4 "2022-12-16T20:01:32Z")

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This is the tag that expression ar located.

 ![image](https://us1.discourse-cdn.com/inductiveautomation/original/3X/5/6/565c149c94fbd51fcf39ad03b596e14bc000b55a.png)  
How can I work it arround? Its a HMI schedule time programmer.  
 ![image](https://us1.discourse-cdn.com/inductiveautomation/original/3X/5/a/5aa4b34c439735906f435b7c2c2d98236c78f00b.png)  
Its changes the tag status to level one when the time to turn it on comes, and to level zero to turn it of when the time comes if it is enabled.

DO you know how can I make it works?

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<div class="post-metadata">

**Author:** ![pturmel](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/pturmel/32/3295_2.png) [@pturmel](https://forum.inductiveautomation.com/u/pturmel)\
**Post date:** [December 16, 2022, 8:13pm UTC](https://forum.inductiveautomation.com/t/issue-to-expression-tag-in-iginition-8-1/67730/5 "2022-12-16T20:13:00Z")

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> [@Leandro\_Garcia\_Carva](#):
>
> you know how can I make it works?

Find out where something else is writing to that expression tag. Delete that part, or incorporate it into the expression. Only the calculation of the expression is allowed to provide that tag's value.