# Fixed rate in expression tags **URL:** \ **Category:** Ignition\ **Created:** [December 11, 2020, 3:21pm UTC](https://forum.inductiveautomation.com/t/fixed-rate-in-expression-tags/41424 "2020-12-11T15:21:20Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![deforder](https://avatars.discourse-cdn.com/v4/letter/d/aeb1de/32.png) [@deforder](https://forum.inductiveautomation.com/u/deforder)\ **Post date:** [December 11, 2020, 3:21pm UTC](https://forum.inductiveautomation.com/t/fixed-rate-in-expression-tags/41424/1 "2020-12-11T15:21:20Z")
I have an expression tag that needs to be recalculated once per second. The expression is very simple (adds the value of another memory tag). I am using a fixed rate 1000ms. But recalculation occurs every 15-20 seconds. Why might this be happening? What else affects the recalculation period? Memory and CPU are used by 20% Thanks in advance/ ---
**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:** [December 11, 2020, 3:26pm UTC](https://forum.inductiveautomation.com/t/fixed-rate-in-expression-tags/41424/2 "2020-12-11T15:26:04Z")
Possibly other tags in the scan class/tag group are stalling the rest. (What version of Ignition?) Tags use a thread pool to manage multiple tasks, so it is possible to stall, especially with tag events that execute long-running code. Consider making a tag group just for this item. Also consider using a gateway timer script to do this instead of an expression. ---
**Author:** ![enertec](https://avatars.discourse-cdn.com/v4/letter/e/e9bcb4/32.png) [@enertec](https://forum.inductiveautomation.com/u/enertec)\ **Post date:** [December 28, 2020, 11:46am UTC](https://forum.inductiveautomation.com/t/fixed-rate-in-expression-tags/41424/3 "2020-12-28T11:46:13Z")
8.0.16 Same problem Expression tag value execution with big delay consider less tag group period Please advise