Comment by steve_adams_86

That’s right, I’ve dissolved sulphur and potassium bicarbonate into separate containers, and peristaltic pumps dose a small amount every 15 minutes when the nutrient solution goes beyond the acceptable parameters for an hour. 15 minutes is enough time for one dose to register on a read of the pH level so that it doesn’t go too far.

As for EC, I can only correct it if it’s too low. If it’s 100 points below where I want it, I dose from two containers of pre mixed nutrient concentrate. They’re in separate containers because they’ll actually precipitate some of their constituents if they’re combined at high concentrations, which is too bad (it would be nice to use only one container).

The pH sensor I use is apparently lab grade, but only cost around $70 CAD. It has been holding up just fine for close to a year now. If I were doing this on a larger scale, I think I’d go for one that’s a bit more expensive from atlas scientific. They seem to stand by their products and claim their pH probes will operate for years if taken care of.

My EC sensor was quite a bit more — something like $150. I forget where I got it, because I had the idea to build this maybe 10 years ago and that was one of the first components I picked up! Looking around it seems like you can spend quite a bit less now, and it seems like they’re durable.