The last watering they would have gotten was around 5am. You can see the steady march upward as the lawn dried out starting around 14:30. The blue line is the sprinklers going off. (ignore the smaller blips, those are the drips, the one we care about is the big spike at 5am). At 5am the sprinklers fire off for 5 minutes each. You can see how two of the sensors respond to this immediately (1 and 4), but the other two are a bit more slow. 1 and 4 are the outside pair, and 2,3 are the innermost two sensors, closer to the center of the lawn.
The sensors responded within about 25 minutes on those outer pairs, especially #4. I will be watching this over the next few weeks, and start writing some code to auto-adjust the sprinklers depending on conditions.
According to the Davis sensor manual, "turf does not need to be watered until 25-40cb". I suspect that there needs to be some kind of hysterisys in there, so maybe let it rise to 60 and then knock it back down to 25? Mostly, I need to watch the graphs for a bit, so I can determine exactly how much each valve contributes to the moisture, and how much time per valve is required to move the moisture a specific amount. Once I have this data, I think I can start programming code to make everything automatic.
The benefit of course, should be that the water will automagically self-adjust to deal with the changing of the seasons. That's the theory at least.
Also, side note, given the way sensor 4 responded so radically, it makes me suspect an underground leak. Hrmm.
