Chagrin:
For a load cell subjected to the elements
I'm not super worried about how to keep the thing dry and safe.
What I am worried about is extremes of temperature -- -30C .. +35C would be the range it has to deal with, and the fact that it would be installed permanently under an immovable load of 250Kg
When I use a strain-gauge load cell type scale, they always need to be zeroed out before they will give a useful readings. In my application that would not be easy. No one is going to go lift up a 1,000Kg water tank, or a 250Kg LPG tank, even every few days, just to zero out the load-cell.
Furthermore, when the mechanical linkages that transfer the weight of the tank onto the load cell are also subject to expansion and material property (elasticity) changes due to corrosion, temperature changes, fatigue, creep, age hardening and whatnot, the complexity of a permanent installation such as mine is rather high.
For measuring the water level in a 1,000L tank, it's not a winning approach for me. For measuring the fuel level in an LPG tank, it's likely the best I can hope for.