# Full Tag Path in an expression

**URL:** <https://forum.inductiveautomation.com/t/full-tag-path-in-an-expression/8861>\
**Category:** Ignition\
**Created:** [August 6, 2014, 12:30am UTC](https://forum.inductiveautomation.com/t/full-tag-path-in-an-expression/8861 "2014-08-06T00:30:55Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![matt.eaton](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/matt.eaton/32/72046_2.png) [@matt.eaton](https://forum.inductiveautomation.com/u/matt.eaton)\
**Post date:** [August 6, 2014, 12:30am UTC](https://forum.inductiveautomation.com/t/full-tag-path-in-an-expression/8861/1 "2014-08-06T00:30:55Z")

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So I’m trying to work with intermittent communication with my plcs and to solve the problem I want to get the last good value if the current state is bad quality. I wrote a script that will get me either the current value if it’s good or the last historical if its not.

But here’s my problem. If I make an expression tag that is set to this value then I have to get the full tag path to the OPC tag that contains the value using expressions and I can’t figure out what the reference is for that.

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<div class="post-metadata">

**Author:** ![matt.eaton](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/matt.eaton/32/72046_2.png) [@matt.eaton](https://forum.inductiveautomation.com/u/matt.eaton)\
**Post date:** [August 7, 2014, 3:09pm UTC](https://forum.inductiveautomation.com/t/full-tag-path-in-an-expression/8861/2 "2014-08-07T15:09:05Z")

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I ended up working around this issue by writing a script on the valueChanged event that conditionally writes it’s value and timestamp to memory tags if the quality is good.  
If the live value is returned as null I apply formatting to the display and point at the historical value.

As far as I was able to determine, there is no method to get the full tag path with expressions.