# Same modbus address multiple devices

**URL:** <https://forum.inductiveautomation.com/t/same-modbus-address-multiple-devices/10862>\
**Category:** Ignition\
**Created:** [December 2, 2015, 7:00pm UTC](https://forum.inductiveautomation.com/t/same-modbus-address-multiple-devices/10862 "2015-12-02T19:00:45Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![codersmurf](https://avatars.discourse-cdn.com/v4/letter/c/df788c/32.png) [@codersmurf](https://forum.inductiveautomation.com/u/codersmurf)\
**Post date:** [December 2, 2015, 7:00pm UTC](https://forum.inductiveautomation.com/t/same-modbus-address-multiple-devices/10862/1 "2015-12-02T19:00:45Z")

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I have multiple units with the same software running on the hardware. Is there a way to make a tag that uses a device currently viewed, or being polled?

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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:** [December 2, 2015, 7:12pm UTC](https://forum.inductiveautomation.com/t/same-modbus-address-multiple-devices/10862/2 "2015-12-02T19:12:17Z")

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This might not be exactly what you’re asking, but since all the tags would have the same addresses for each device you could make a UDT where the device name was a parameter and the OPC item path for all the tags in the UDT are built using that device name.

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**Author:** ![codersmurf](https://avatars.discourse-cdn.com/v4/letter/c/df788c/32.png) [@codersmurf](https://forum.inductiveautomation.com/u/codersmurf)\
**Post date:** [December 2, 2015, 7:41pm UTC](https://forum.inductiveautomation.com/t/same-modbus-address-multiple-devices/10862/3 "2015-12-02T19:41:42Z")

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That sounds about right, what is a UDT and how do I get the variable replacement. Also, I want the opc server to still grab all the tags from all the devices for BI purposes.

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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:** [December 2, 2015, 8:06pm UTC](https://forum.inductiveautomation.com/t/same-modbus-address-multiple-devices/10862/4 "2015-12-02T20:06:02Z")

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[inductiveuniversity.com/course/tags/#25](https://inductiveuniversity.com/course/tags/#25)

Check out the topic “Creating User Defined Types (UDTs)”

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<div class="post-metadata">

**Author:** ![codersmurf](https://avatars.discourse-cdn.com/v4/letter/c/df788c/32.png) [@codersmurf](https://forum.inductiveautomation.com/u/codersmurf)\
**Post date:** [December 2, 2015, 8:32pm UTC](https://forum.inductiveautomation.com/t/same-modbus-address-multiple-devices/10862/5 "2015-12-02T20:32:05Z")

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Awesome, thx, I’ll check this out.