Originally Posted by Chuck
so, nobody can explain the how the circuitry of a conventional tank probe/level gauge system works?
The most likely scenario is one common probe, and two sensing probes. the common probe would be the lowest.
When the tank fluid reaches the second lowest probe, a small current would be allowed to flow between the lowest and second lowest probe due to the impurities in the water. The indicator circuitry would sense this and light the half full light. The same thing would happen when the fluid reached the highest probe and the full light would illuminate.