DIN 12791-1:2018-12

This document lays down requirements for five basic series of constant mass glass hydrometers with built-in thermometer, i.e. thermal hydrometers (Th) or without built-in thermometer, indicating the density in kg/m3 or in g/ml at 20 °C. Each of these basic series contains hydrometers covering a total measuring range from 600 kg/m3 to 2000 kg/m3 (0,600 g/ml to 2,000 g/ml). The hydrometers are adjusted for determining the density of liquids with low, medium or high surface tension. In addition, three sub-series (Sp) are described where the reference temperature is 20 °C or 15 °C. They have narrower error limits and are limited to the range 600 kg/m3 to 1100 kg/m3 (0,600 g/ml to 1,100 g/ml). The hydrometers meet the requirements of DIN 12790.