Yes that work too. I didnt have an open PH slot on my Apex so that is why I use a PM1 module.I have the ph in the co2 already connected to the PH2 on my apex. Would I be able to ise that, instead of buying a new pm1?
Here is what I use for my code (The PH numbers would be adjusted up or down depending on your needs):
Fallback OFF
If CaRxPH > 7.10 Then ON
If CaRxPH < 7.00 Then OFF