hsteve

I've been thinking of a new DIY project, namely a DIY pH controller. I've got a basic knowledge of electronics, and think this would be a fun project to try.
The idea is to take a standard pH probe and hook it up to an interface that connects to my computer. The output of a probe(I think) is voltage, so it should be a relatively easy task to wire the probe to a circuit that either steps up or down the output voltage to a value that my 'puter should be able to interpret...then have the computer open a solenoid to inject CO2 to lower, and close it to stop.
Does anyone have any ideas, or sources for the circuitry?
Thanks in advance,
- Steve