Conductivity Sensor

Hi,

I'm constructing a Hydroponics system, and need to monitor the conductivity of the nutrient solution.

Any suggestions on what to use for the sensors for stable long-term readings?

Thanks,
--
Luhan Monat: luhanis(at)yahoo(dot)com
http://members.cox.net/berniekm
"Any sufficiently advanced magick is
indistinguishable from technology."
.