Abstrait

Design and Validation of an Automated Hydrometers Calibration System

M.H. Mohamed, M.A. Bayoumi, Alaaeldin A. Eltawil, A. E. Abuelezz

Liquid density measurement is an important activity in many laboratories. Usually hydrometers are used to measure the density of liquids in the range from 600 kg/m3 up to 1850 kg/m3. For the purpose of metrological traceability of Hydrometers with the international density reference standards a calibration system has been designed, constructed and validated at the National Institute for Standards, NIS, Egypt. The system covers the range from 500 kg/m3 up to 2000 kg/m3. The system is automatically operated for the intended measurements and calibrations using hydrostatic weighing (Cuckow’s method). Distilled water was used as a reference liquid. Finite element analysis using (ABAQUS) software for 3D has been used to check the stress, deformation, rigidity, stability as well, to optimize the design of the system. A laser light source and two linear encoders are used to position the standard liquid surface at the hydrometer scale mark during calibration process. For accurate measurements of scale mark position, an image processing technique combined with a high resolution CCD camera for capture the reading during calibration is used. Lab VIEW program is designed to processing the reading from measurement instruments in a fully automated mode. The calibration results present an expanded uncertainty (with a coverage factor of k= 2) less than 100 ppm. The apparatus’s performance has been validated by comparing the output results of the system versus Laboratoire National de Metrologie et d’Essais “LNE” calibration certificates of 3 standard hydrometers.