# How to log and graph a variable only on specific conditions (non-periodic Tag Historian) **URL:** \ **Category:** Ignition\ **Tags:** vision, ignition81\ **Created:** [July 4, 2025, 8:53pm UTC](https://forum.inductiveautomation.com/t/how-to-log-and-graph-a-variable-only-on-specific-conditions-non-periodic-tag-historian/108149 "2025-07-04T20:53:55Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![maury.sanchez](https://avatars.discourse-cdn.com/v4/letter/m/91b2a8/32.png) [@maury.sanchez](https://forum.inductiveautomation.com/u/maury.sanchez)\ **Post date:** [July 4, 2025, 8:53pm UTC](https://forum.inductiveautomation.com/t/how-to-log-and-graph-a-variable-only-on-specific-conditions-non-periodic-tag-historian/108149/1 "2025-07-04T20:53:56Z")
Hi all, I’m using Ignition 8.1.48 with the Vision, Tag Historian and SQL Brigde modules, and I need help setting up historical logging for a tag only when a certain condition is true — for example, when a tag is 1.. Here’s what I need to do: - Start logging a tag value only while a condition is true. - Stop logging when the condition goes false. - Plot the logged values later in an Easy Chart. - Make sure the data is stored in the database, not just in memory. I don’t want the tag to be logged continuously. I only want to store values while something is happening, like when a tag is ON, and stop when that tag is OFF. What’s the best way to approach this in **Vision**? Things I’ve considered: - Enabling/disabling the historian dynamically (not sure if that’s possible in Vision). - Using a memory tag with history enabled and writing to it conditionally. - Using `system.tag.storeTagHistory()` to manually push values into the historian. Any examples or recommendations would be much appreciated! Thanks! ---
**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:** [July 4, 2025, 9:57pm UTC](https://forum.inductiveautomation.com/t/how-to-log-and-graph-a-variable-only-on-specific-conditions-non-periodic-tag-historian/108149/2 "2025-07-04T21:57:39Z")
The tag historian doesn't directly support this. The SQL Bridge module is designed to do exactly this, with a suitable trigger and period. You can also use a gateway timer event script to do this. ---
**Author:** ![Rick\_de\_Man](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/rick_de_man/32/75670_2.png) [@Rick\_de\_Man](https://forum.inductiveautomation.com/u/Rick_de_Man)\ **Post date:** [July 5, 2025, 5:55am UTC](https://forum.inductiveautomation.com/t/how-to-log-and-graph-a-variable-only-on-specific-conditions-non-periodic-tag-historian/108149/3 "2025-07-05T05:55:57Z")
What if we toggle the Enabled property for Historian using scripting? ---
**Author:** ![Chris\_Bingham](https://avatars.discourse-cdn.com/v4/letter/c/e5b9ba/32.png) [@Chris\_Bingham](https://forum.inductiveautomation.com/u/Chris_Bingham)\ **Post date:** [July 5, 2025, 1:32pm UTC](https://forum.inductiveautomation.com/t/how-to-log-and-graph-a-variable-only-on-specific-conditions-non-periodic-tag-historian/108149/4 "2025-07-05T13:32:41Z")
If you're okay with the tag not updating at all when the condition is not met, you could utilize a driven tag group, configured so that the tag only scans (and stores history) based on your condition. Follow the [Driven Tag Group Examples](https://www.docs.inductiveautomation.com/docs/8.1/platform/tags/tag-groups/driven-tag-group-example), except set the `Rate` to 0 seconds. ---
**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:** [July 5, 2025, 3:46pm UTC](https://forum.inductiveautomation.com/t/how-to-log-and-graph-a-variable-only-on-specific-conditions-non-periodic-tag-historian/108149/5 "2025-07-05T15:46:40Z")
> [@Rick\_de\_Man](#): > > What if we toggle the Enabled property? That should work, with some changeover delay. But note that is a tag **configuration** property, and there is overhead and internal DB churn for doing that. ---
**Author:** ![robertm](https://avatars.discourse-cdn.com/v4/letter/r/ea5d25/32.png) [@robertm](https://forum.inductiveautomation.com/u/robertm)\ **Post date:** [July 5, 2025, 4:12pm UTC](https://forum.inductiveautomation.com/t/how-to-log-and-graph-a-variable-only-on-specific-conditions-non-periodic-tag-historian/108149/6 "2025-07-05T16:12:44Z")
Seems to me it woud be better to do this at the tag value source level. If it's a PLC, clear the tag that's historized when the condition is false.