Salt Level Measurement
I have been thinking about this idea of weights and strings...
In a saline solution there are likely to be problems with corrosion on any ferrous components
AND
when the salt reservoir is refilled each weight will have to be lifted so that they are supported by the salt and not still actuating the switch.
This seems to be a problematic design.
If you fabricate a carrier rod with a vertical slot in it, on one side of this slot is a row of LEDs, on the other side is a matching row of phototransistors, each pair forming a light beam that can be interrupted by the solid salt ... the whole thing can be plastic and water-tight, no corrosion, no moving parts.
It would be relatively simple to create a column with a detector every inch to give a reasonable resolution on some form of indicator panel, a 'mimic' column of LEDs or (via a simple resistor D-A) on a moving coil meter.
:?: