IR tachometer, weird readings

Hi Tom, you are correct. That’s the sensor I’m using. I’ve also tried this one...

Twidec/10mm Hall Effect Proximity Sensor Inductive Switch NPN NO(Normally Open) with Magnet DC5-30V NJK-5002C https://www.amazon.com/dp/B07P1GKQRM/ref=cm_sw_r_cp_api_i_C1oEDbTBHRNA7

I’m not in front of the setup at the moment but will be happy to post a picture later when I can.

I’m not sure what software I’d use to create the circuit diagram.

And I do have a scope but haven’t broken it out and hooked it up on this yet.