What they said above, but also consider when you add more nutes it will lower PH too (as well as raising EC), so you don't really wanna be adding a specific PH down product unless PH is still way too high after a fresh feeding.
I'm not sure how this new high tech stuff works, but if possible, it might be sensible to just tell it to add PH down if it drops below say 5.5 for example and only let it bring PH up to say 5.6, as your PH will drift upward naturaly anyway as you'll be adding plain water inbetween 'feed doses' as the plant drinks but you'll not want EC to get too high.
Although, thinking about it, I might be talking crap, as if this automated system controls EC too, I guess you set a specific target PH and target EC value, and it does the rest?
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So the way the unit works is it it's a monitor for temp/pH/TDS. I'm still not 100% sure how the functionality works but it refers to the ppm level as "EC". Then you can set trigger points to have solenoids turn on and off based upon the points you set and that works for pH and the ppm level.
So what I did was hook up a tiny peristaltic pump to a reservoir of pH down and if it goes above 6.2 it turns the pump on and as soon as the meter reads 6.19 it turns it off, which usually a few drops have come out and it'll go down to like 5.7.
But honestly my pH has been super stable at 5.97-6.06 and my ppms have been fluctuating but center around 825ppm +/- 10 ppm