Level Measuring Problem

they usually use IR detectors and shine a bright IR beam across at a height. (IR penetrates dust better). Once the contents fall below the beam it can be detected by the detector and a signal given to fill. This can be automated and there can be several levels

If material to be measured has the same consistency, more or less, when loaded into the tank, meaning that it will always have the same weight per unit volume, than your best bet is capacitive measurements. This is relatively simple equipment and is easily obtainable. Load cell are also good solution, and you don't have to hang the whole tank on the load cell.

Wangito