On Fri, 08 Dec 2006 13:26:50 +0000, Nikki Casali
wrote:

snip

I was thinking of getting the Milwaukee sms122. I hesitate as I
understand it requires monthly recalibrating.

It's the pH probe that will drift that will require the controller to be
adjusted. Nothing varies within the controller itself to warrant a
recalibration on that count - unless the components are adversely
affected by ambient temperature change. A monthly recalibration is just
a guideline. I recalibrate my controllers once a week because I find the
probes can drift a bit and can be affected by algae build up.

Thanks. That makes sense. So is there a particular pH probe I should
look for that is more reliable i.e. doesn't drift so easily? I'm
assuming any pH probe with the standard BNC connector will be
compatible with the controllers we've been discussing?