Hello,
Does anyone know how devices like these work: VOLTCRAFT MF-100 Moisture indicator | Conrad.com
.... and if so how one might go about replicating this on Arduino?
I know they use capacitance and there is only one contact.... the large alluminium ball that touches the material to be measured.... beyond that I'm stumpppped.
All thoughts appreciated 
Most likely device measures absorption of energy radiated from antenna. Freq. around peaks in water spectral chart, 2.4 GHz and up to 60 GHz .
The most difficult part of course, generator and detector. Arduino can only measure and display after that.
Thanks Magician,
I have just hooked up a scope to the probe and it looks like its chucking out a nice sine wave at about 50Khz @ VRMS 90mV - both these figures reduce quite a bit when the probe gets near water based materials.
Wonder if anyone knows a circuit that would allow the sensing side to be done before passing it over to arduino for display?