# Scale reading value with engineering limit for historical trend

**URL:** <https://forum.inductiveautomation.com/t/scale-reading-value-with-engineering-limit-for-historical-trend/47749>\
**Category:** Ignition\
**Tags:** ignition79, scripting\
**Created:** [June 14, 2021, 3:16pm UTC](https://forum.inductiveautomation.com/t/scale-reading-value-with-engineering-limit-for-historical-trend/47749 "2021-06-14T15:16:04Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![jamshidzade](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/jamshidzade/32/24927_2.png) [@jamshidzade](https://forum.inductiveautomation.com/u/jamshidzade)\
**Post date:** [June 14, 2021, 3:16pm UTC](https://forum.inductiveautomation.com/t/scale-reading-value-with-engineering-limit-for-historical-trend/47749/1 "2021-06-14T15:16:04Z")

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I am reading two value from the Modbus device, whenever the pH device is calibrating the trend show 327  
I was scaling the value in the device 0-14, but when they shut down or calibrate the device it’s how 327  
I scale value in engineering unit low 0, and high 14 and engineering limit enforcement enable for both  
but still reading high or negative  
do you have any idea  
do you think I have to write the script for the tag event

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**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:** [June 14, 2021, 3:46pm UTC](https://forum.inductiveautomation.com/t/scale-reading-value-with-engineering-limit-for-historical-trend/47749/2 "2021-06-14T15:46:00Z")

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Engineering limit enforcement applies only to **writes** , if I recall correctly. Consider using a derived tag to yield a clamped value.

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**Author:** ![jamshidzade](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/jamshidzade/32/24927_2.png) [@jamshidzade](https://forum.inductiveautomation.com/u/jamshidzade)\
**Post date:** [June 14, 2021, 4:40pm UTC](https://forum.inductiveautomation.com/t/scale-reading-value-with-engineering-limit-for-historical-trend/47749/3 "2021-06-14T16:40:45Z")

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Thanks

Clamped both 0 to 14 and will let you know the result