The effect of density gradients on hydrometers

Hydrometers are simple but effective instruments for measuring the density of liquids. In this work, we studied the effect of non-uniform density of liquid on a hydrometer reading. The effect induced by vertical temperature gradients was investigated theoretically and experimentally. A method for compensating for the effect mathematically was developed and tested with experimental data obtained with the MIKES hydrometer calibration system.In the tests, the method was found reliable. However, the reliability depends on the available information on the hydrometer dimensions and density gradients