Firstly you need to know the application, and any special conditions, whether you require a submersible, contact type, a Infra-red or Microwave (non-contact) type, etc...etc..
It often helps, if you describe all the details firstly and then ask questions.
my interest in this was that I too am looking for a Non-contact Moisture sensor, But I have another cheaper idea, and would want to know views of some Electronic champs around here, as I am into automation, (but not an electronic Engineer), What I want is to meaure the moisture of Product, (Contact type) by measuring the Conductivity/Resistance, draw a table, and convert them in the PLC and give out the result, PLC is no problem for me, ButI am looking for someone who could guide/assist me how to construct this SUPER DOOPER capacity Sensor (You can take an example of the Multi meter set to Conductivity/Resistance, with super sensitivity.)
Would apprecite any help at iel@cyber.net.pk [sig][/sig]