EC and PPM readings are wonky

Gotcha, thanks :+1::v::green_heart:

The issue people are running across is they’re going by the fox farm recommended Ppm not knowing that fox farms is on the 700 scale and most of our meters are reading on the 500 scale. 1750-2100ppm on the 700 scale is actually 1250-1500ppn on the 500 scale. I need to look to see if there’s a 500 scale version for the fox farms schedule. If not, I’ll make one so it can be passed around.

If people stay on the low end of the range on their feed schedules, the highest ppm fox farms calls for is 1500.

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And to make it all more confusing, it’s a ‘theoretical’ number as a number of solids don’t change the electrical conductivity of the solution (sugar is one) and the only reliable benchmark for determining the solution concentration is to weigh it with and without the water present. We use these as a convenience and for all practical purposes they are close enough for MJ work. That is one reason growers will say ‘around 900 ppm’.

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I personally use it as a reference. If I have a problem, I have a tangible number to look at to compare with what I plan to feed to fix it. 900ppm might be just right for one plant, and might burn the hell out of another, so I feel it’s best to go by what the plant wants.


Here we go. Forgive my poor paint skills


Thanks for taking the time to do that @BobbyDigital it will definitely benefit a lot of FF users.

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