Originally Posted by jeffmeh
Perhaps I am missing something, but are you saying you use autotune to mash? That doesn't make sense to me, as autotune should "experiment" to determine the heating and cooling characteristics of the system (e.g., overshoot as a means to subsequently determine the cooling rate). But if it ain't broke, don't fix it.
Yes, when I first started up I followed some instructions I found on this site and I auto tuned with water. Then I started mashing with the settings the PID learned.
Later I read an article stating that in most cases you could just leave auto-tune on. The article was not about mashing, it was about heating a green house, but it still used my PID controller. I tried my next batch with the auto tune left on and it held temperature just fine, so I started reading the P,I & D after each batch and they varied but not my much. Apparently the auto tune does not start over, instead it starts with the last settings.
Now I need to record the P,I & D readings through the mash process. If the PID is auto tuning based on need then I would expect the auto tune values to be different between the start of the mash and the end of the mash because the heat demand is different. Not only does my mash need more heat to raise from strike temperature to mash temperature, my basement is also a lot warmer at the end of my mash.