Performance Evaluation of a Digital Density Meter Method for High-Precision Hydrometer Calibration
摘要
Accurate calibration of density hydrometers is critical for many applications. This study evaluates an alternative calibration method using a Digital Density Meter (DDM) and compares its performance against the established hydrostatic weighing technique (Cuckow's method). Full description of the proceeding methods is described. Experiments were conducted using three reference liquids at controlled temperatures (20 °C, 23 °C, and 25 °C) to calibrate different ranges of hydrometers: three with high resolution (0.0001 g/cm3) and three with lower resolution (0.001 g/cm3). The influence of the DDM's precision was also analyzed. According to the calibration results, the errors obtained using the DDM method and the hydrostatic weighing technique range from 31 to 95 ppm. The expanded uncertainty of the DDM method is approximately twice that of the hydrostatic weighing technique. Three statistical methods are used to evaluate the performance for each method (weighted mean reference value and Chi-squared consistency test and degree of equivalence test. For the high-resolution hydrometers, calibration compared with a 6-digit DDM yielded a standard uncertainty of approximately 122 ppm. This uncertainty is projected to increase only slightly to 126 ppm and 205 ppm for 5-digit and 4-digit DDMs, respectively. For the lower-resolution hydrometers (3-digit), the hydrometer's resolution became the dominant source of uncertainty, resulting in a standard uncertainty of approximately 353 ppm, with negligible impact from the DDM's precision. The results validate the DDM-based method as a robust alternative to hydrostatic weighing and provide a clear framework for estimating the achievable uncertainty for hydrometers of different resolutions.