Who usually does your homework?

LOL, who's being a tad cheeky then, and I see that you didn't feel
confident to give an answer yourself My last pre-uni homework was a
couple of decades ago, but I agree that it does sound like a homeworky
type thing. I had looked at WP earlier, but thanks to Dave for the
other link.

I was actually wondering in relation to the irrigation aspect of a
computer controlled landscape project that I'm working on covering
irrigation, lighting, audio etc. Our irrigation controllers coupled
with techline and other devices should keep the watering nicely under
control, and the plan is to have watering schedules adjusted
automatically by the controller in part from predictive weather
forecasts from sources such as the Beeb. However I was also thinking
about getting feedback from the soil about how things are going by
adding some RF moisture sensors to remotely monitor irrigation
effectiveness and to factor that into the schedules. I knocked
together a simple proof of concept moisture sensor last night using
the most basic tried and tested method (AC resistance) and that seems
to work very well with no drift due to ionisation, but it had me
thinking about testing and calibrating. That said, due to the
limitations of the resistance technique I'm expecting to make the
sensors auto-calibrate themselves to sufficient resolution in the
field so to speak as any attempt at pre-calibration may be useless,
but I was still curious about what adding a given amount of water
actually means in terms of moisture content.