Simply structured and non-electric weight scale for liquid nitrogen tanks

With the aim for the easy estimation, as a daily work, of volume of liquid nitrogen in metal tanks in which liquid nitrogen cannot be observed directly, in the present paper a simply structured and non-electric weight scale is proposed. The proposed weight scale consists only of a bedplate with vibration suppression rubber to lift liquid nitrogen tanks, an L-shape component connected to the bedplate, and a conventional ruler. The principle of the mass measurement is the following. The length of the rubber working as spring material changes depending on the amount of liquid nitrogen, i.e. the mass of a liquid nitrogen tank, following the classical Hooke’s law; hence, the height of the bedplate also changes. The L-shape component detects the vertical displacement of the bedplate, magnifies it by the ratio of the two arms of this L-shape component, and converts into a horizontal displacement. This magnified displacement is measured with the conventional ruler. With this weight scale the mass and volume of liquid nitrogen in tanks can be estimated with the accuracy of 1.0 kg and 1.2 L, respectively. This accuracy of the proposed scale is not small but within an acceptable range for the rough estimation of liquid nitrogen. Only the Hooke’s law and elemental geometry with some trigonometric functions are utilized to construct the proposed weight scale; thus, even in high school and university students can construct and repair this scale by themselves. Moreover, the proposed weight scale may also be suitable for an educational material for classical physics in the field of education in high school and university.