uses bead thermistors sticked to to the tank as sensors
http://www.mitedu.freeserve.co.uk/Circuits/Misc/hwtank.htm
capacitance type
http://www.discovercircuits.com/PDF-FILES/capgage.pdf
I n most houses, water is first stored in an underground tank (UGT) and from there it is pumped up to the overhead tank (OHT) located on the roof. People generally switch on the pump when their taps go dry and switch off the pump when the overhead tank starts overflowing. This results in the unnecessary wastage and sometimes non-availability of water in the case of emergency.
http://www.electronicsforu.com/electronicsforu/Lab/freecircuitslist.asp?id=247
Here is a simple, versatile cir- cuit which indicates the level of water in a tank. This circuit produces alarm when water level is below the lowest level L1 and also when water just touches the highest level L12.
http://www.electronicsforu.com/electronicsforu/Lab/freecircuitslist.asp?id=48
Here is a simple, versatile cir- cuit which indicates the level of water in a tank. This circuit produces alarm when water level is below the lowest level L1 and also when water just touches the highest level L12.
http://www.electronicsforu.com/efylinux/circuit/cir105.htm