So what is Galvanic isolation? Well, the tech-answer is that it’s where two or more electric circuits must communicate, but their grounds may be at different potentials. It is an effective method of breaking ground loops by preventing unwanted current from flowing between two units sharing a ground conductor.
Now of course that is all geek-speak to most of us so let’s just put it this way: on a controller without galvanic isolation, your readings of pH, Temperature, ReDox (ORP), Conductivity/Salinity, etc. will be completely inaccurate. Of course it costs us more to add this circuitry into the Apex, but what good is a controller if it doesn’t give you accurate readings?