PURPOSE: To improve displaying accuracy, by switching display segments in a non-displaying state into a displaying state when a voltage corresponding to the remaining quantity of liquid becomes lower than a specified value, and expanding and displaying the region where the remaining quantity of the liquid is few.

CONSTITUTION: A voltage V- corresponding to the remaining quantity of liquid is generated across a slider 102 and a terminal (b). The voltage V- is compared with a specified value V+, which is set by resistors 303 and 304, by a comparator 301. When V+>V-, an output voltage V0 of the comparator 301 keeps an L level, a transistor 302 is in an ON state, a resistor 305 is shorted, and a voltage V is applied to a terminal (c). The display states of display segments 401W406 become non-display state in correspondence with the outputs of comparators 211W216. When V+<V-, the transistor 302 is turned OFF. A voltage, which is decreased by the resistor 305, is applied to the terminal (c). The comparators 211W216 are switched to new reference values. Therefore the region, where the most important quantity is few, can be displayed in detail without the operation of a switch.