RE:CO2 controller

> (FWIW, they also sold
> me a new pH probe, because the original, after 8 months, would no
> longer register under 14.3.  Unfortunately, the "new" one won't read
> above -3.5, so I'll be doing without the controller for a while.)

This definately sounds like a controller problem and not an electrode problem.
It sounds like that the reference inside the controller has a problem, and that
the amplifier is going into saturation somehow.