Abstract: A display apparatus which will numerically indicate the quantity of fluids removed from any tank or tanks by accepting the output from a unit inserted in each tank which varies in resistance from minimum to maximum as the tank moves from a full to an empty condition respectively. The apparatus applies a constant current to the variable resistance and develops a current which changes from minimum to maximum as the tank is emptied. An amplifier accepts the variable current along with a comparison current and converts the differential current to an output current. The current is subsequently applied to an adjusting companion fixed voltage. The display reads the different voltage, and displays the difference, which represents the level or final quantity remaining in the tank. The circuit can also indicate the level of each of several tanks with adjustment in the calibration of the system for each tank.