Water management system

[cheerio]

I filled half of the cistern with fresh water. the water level measurement was very precise <1cm. After a while we had a rainy week and the measurement screwed totally up. The deviation was about 10cm. I will calibrate the meter again when there is only rain water left.
I am curious about what parameter changed the measurement so extreme. If i knew i could make this sensor adapting.

[kam]

i totally put my money on water composition. rain water can have much much less PH and different density than normal water.

[cheerio]

absolutely kam. but what parameter of the water composition is responsible? I bet the PH has nothing to do with it. Maybe the EC?

[kam]

probably the density and the impurities which lead to non-uniform liquid

[cheerio]

Did work on this for a while longer. and right now i am rebuilding all of it because it looks like shit
i want it to be tight and nice. will put something more up here soon