Moku:Lab's Laser Lock Box : When and how should I use the slow PID controller?

Moku:Lab has fast and slow PID controllers

When stabilizing lasers, it is common to need to provide feedback control loops to multiple actuators.

A common situation involves one fast actuator with limited range (e.g. current or piezo);  and one slow actuator with a much larger range (e.g. temperature).

The slow PID controller acts on the fast PID controller’s output, keeping it centered around zero and thus maximizing the dynamic range for the fast feedback control.