I am interested in building a Master Pool Controller like Loulou74 present back in 2021. Anyone built this and if so what did you use for level indication on the chlorine and acid supplies?
For chlorine and acid supplies I would probably avoid putting any sensor into the liquid at all.
Put each container on a load cell and measure its weight, e.g. with an HX711 interface. Tare the empty container and calibrate it once when full, and you can calculate the remaining amount quite accurately.
That avoids most of the chemical compatibility and corrosion problems you would get with floats, probes, etc. — particularly with chlorine and acid.
Not sure what you mean by levels of chlorine and acid supplies.
I'm assuming you mean the concentrations of acid and free chlorine in the pool water.
Acid is straightforward with a pH probe. It should be OK for long term use at say a range of 6 to 8 pH.
How are you dosing your chlorine? Gas from a cylinder, Fichlor Sodium Dichloro Isocyanurate (SDIC) or hypochlorite solution?
I'm guessing if you need acid, you might be using hypochlorite.
Traditionally, chlorine is measured colorimetrically or with test strips. There might be a sensor that I'm not aware of.
The problem with hypochlorite is that over time the sodium concentration builds up, same with Fichlor.
pH needs regular calibration with buffer solutions and temperature compensation, so a good suite of sensors might be pH, conductivity, temperature and possibly chlorine.
Large scale chlorination is quite complex. A large dose of chlorine is added first, super chlorination, then sulphur dioxide is added to bring the chlorine concentration back down to a tolerable level.
How big is the pool? Indoors?