How do you determine if your moister is at its optimum? --- I am putting in automatic watering and building the entire system, including the sensors. I need to calibrate this control mechanism for best plant conditions. (I will be gone several times during the season, sometimes for days) Too wet and too dry are obvious, however is there a simple way to determine that just right range for best plant health? If I find a good way to determine this, then I can calibrate my system to help me out when I"m gone.