Here we define 7 levels in thereservoir. The sensed values are connected to an encoder circuit. The encoder circuit consist of a 74148 IC, which is a 8 line to 3 line encoder. Next section is the HEX Display` which is a special type of 7 segment display. It is easier to use than the regular seven-segment display because it is already decoded. Each
hexadecimal digit is displayed when its 4 bit binary equivalent is received as input, as shown in the truth table below. If it is difficulty to get a HEX Display` you can use ordinary 7 segment display with decoder driver IC 7447. Hence the encoded values are displayed. This circuit will be really helpful for your project. You can neglect the 4th input (D) of 7447 because we are using this circuit to code up to 7 level, that is upto binary 111. Hence there is no need of the 4th input of 7447.