# Smallest value Ignition can read from OPC/Tag

**URL:** <https://forum.inductiveautomation.com/t/smallest-value-ignition-can-read-from-opc-tag/19563>\
**Category:** Ignition\
**Tags:** ignition79\
**Created:** [September 6, 2018, 2:58pm UTC](https://forum.inductiveautomation.com/t/smallest-value-ignition-can-read-from-opc-tag/19563 "2018-09-06T14:58:27Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![kairongsen](https://avatars.discourse-cdn.com/v4/letter/k/eb9ed0/32.png) [@kairongsen](https://forum.inductiveautomation.com/u/kairongsen)\
**Post date:** [September 6, 2018, 2:58pm UTC](https://forum.inductiveautomation.com/t/smallest-value-ignition-can-read-from-opc-tag/19563/1 "2018-09-06T14:58:28Z")

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Greeting.  
Did anyone know the smallest value Ignition can read from OPC/Tag?  
My colleague and I were working on a project that required to read the value from a Tag with 10^-17 and inside Ignition, the value obtained is 0.  
I search through this  
[https://docs.inductiveautomation.com/pages/viewpage.action?pageId=6718387](https://docs.inductiveautomation.com/pages/viewpage.action?pageId=6718387)  
but nothing is related.  
Thanks

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**Author:** ![paul-griffith](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/paul-griffith/32/37249_2.png) [@paul-griffith](https://forum.inductiveautomation.com/u/paul-griffith)\
**Post date:** [September 6, 2018, 3:18pm UTC](https://forum.inductiveautomation.com/t/smallest-value-ignition-can-read-from-opc-tag/19563/2 "2018-09-06T15:18:31Z")

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This will depend on the datatype of the tag (and is subject to scaling wherever it’s coming from) but a double tag should have a hypothetical minimum value of 2⁻¹⁰⁷⁴:  
[https://docs.oracle.com/javase/7/docs/api/java/lang/Double.html#MIN\_VALUE](https://docs.oracle.com/javase/7/docs/api/java/lang/Double.html#MIN_VALUE)

Make sure that you’re also changing the number format of the tag to actually be able to display all those digits.

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**Author:** ![kairongsen](https://avatars.discourse-cdn.com/v4/letter/k/eb9ed0/32.png) [@kairongsen](https://forum.inductiveautomation.com/u/kairongsen)\
**Post date:** [September 6, 2018, 3:20pm UTC](https://forum.inductiveautomation.com/t/smallest-value-ignition-can-read-from-opc-tag/19563/3 "2018-09-06T15:20:40Z")

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Greeting Sir. Thanks for ur reply. Can I come back to u after I try on it?

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**Author:** ![kairongsen](https://avatars.discourse-cdn.com/v4/letter/k/eb9ed0/32.png) [@kairongsen](https://forum.inductiveautomation.com/u/kairongsen)\
**Post date:** [September 10, 2018, 12:49am UTC](https://forum.inductiveautomation.com/t/smallest-value-ignition-can-read-from-opc-tag/19563/4 "2018-09-10T00:49:43Z")

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Hi I manage to solve the problem by changing the data format but I dont know why when I manually assigned the tag path to the field number it wouldn’t show the true value. The true value will only be shown when I direct drag the tag and map to the field number

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<div class="post-metadata">

**Author:** ![kairongsen](https://avatars.discourse-cdn.com/v4/letter/k/eb9ed0/32.png) [@kairongsen](https://forum.inductiveautomation.com/u/kairongsen)\
**Post date:** [September 10, 2018, 4:26am UTC](https://forum.inductiveautomation.com/t/smallest-value-ignition-can-read-from-opc-tag/19563/5 "2018-09-10T04:26:35Z")

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I modify the deadband and everything seem to work fine now. Thanks