# Tacho input to PMU 24

**URL:** <https://community.ecumaster.com/t/tacho-input-to-pmu-24/3575>\
**Category:** GENERAL\
**Tags:** how-to\
**Created:** [April 25, 2025, 1:39pm UTC](https://community.ecumaster.com/t/tacho-input-to-pmu-24/3575 "2025-04-25T13:39:13Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![Gareth](https://avatars.discourse-cdn.com/v4/letter/g/ba8739/32.png) [@Gareth](https://community.ecumaster.com/u/Gareth)\
**Post date:** [April 25, 2025, 1:39pm UTC](https://community.ecumaster.com/t/tacho-input-to-pmu-24/3575/1 "2025-04-25T13:39:13Z")

</div>

Hi, I have a MSD ignition 6AL which has a 12v square wave output at 20% DC for the Stack dash tacho. Car is on carbs and coil so no ECU.  
What’s the best way to connect RPM to the PMU 24 for logging?

---

<div class="post-metadata">

**Author:** ![FloorItGarage](https://dub1.discourse-cdn.com/flex013/user_avatar/community.ecumaster.com/flooritgarage/32/61_2.png) [@FloorItGarage](https://community.ecumaster.com/u/FloorItGarage)\
**Post date:** [April 25, 2025, 8:46pm UTC](https://community.ecumaster.com/t/tacho-input-to-pmu-24/3575/2 "2025-04-25T20:46:24Z")

</div>

PMU unfortunately doesn’t have a digital input for this.

Does the Stack dash have a CAN connection? You’ll need a device in between the 6AL and PMU to be able to data log rpm.  
I have seen this request a few times now and hopefully in the future the PMU gets revised with a digital input or two…