🚀 go-pugleaf

Thanks from the original poster for all those responces....  I'll look up
the parts for the humidity sensing devices, I'm sure our VLSI lab has the
right catalogs.  Hope they come with some specs (I'm mostly new to this
field) and an example schematic would be terrific (especially the one
from Ohmic Instruments, how I turn variable capacitance into a voltage is
a tab beyond me at the moment).

I (being a former meterologist) knew about wet and dry bulb thermometers.
 One reason I did not want to use this is the life forms in the terrarium
are very dependent on a correct humitidy level.  If the wet part ever
dried out so would the frogs 'n plants as there would be no difference in
temperatures and the curcuit would think 100%RH (right?)!  Supplying
water is the problem here.  Also, at the high humidities (85-95%) found
in the tank, the differenece between wet and dry is not great (ie, not a
lot of water is evaporating) so that the accuracy is not great.  

But hey,  don't stop the ideas!

   mark