PURPOSE:To detect the quantity of a liquid independently of the variation of the liquid surface by standing level gauges in four corners of a self-running measuring tank an reading and operating a maximum value and a minimum value of them when the quantity of the liquid in the tank mounted on an automobile or the other moving body. CONSTITUTION:When the quantity of the liquid stored in a rectangular parallelopiped- shaped or elliptical tank 1 mounted on the automobile or the like is measured, level gaufes 3a-3d are stuck vertically to four corners of the tank 1, and the height of an inclined liquid surface 2 is detected. If the liquid surface 2 is inclined as shown in the figure, the gauge 3a indicates the highest, value and the gauge 3d indicates the lowest value, and these values Hmax and Hmin obtained by a comparator 4 and a length A of the longer side and a length B of the shorter side of the inside face of the tank 1 are used to operate a quantity Q of the liquid. That is, the quantity of the liquid is obtained in an arithmetic unit 5 in accordance with an equation Q= AXBX(Hmax+Hmin)/2 and is displayed on a display device 6. Thus, the accurate measured value is obtained independently of the variation of the liquid surface 2.
