Study On Direct-driven Vibrating Tube Densimeter

Density,as an important physical and chemical parameter,is widely used in mechanics,energy and chemical engineerin filed.It is not only related the development of science and technology,but also contributes to the improvement of international trade techonology.so,accurate density metrology is essential.Vibrating-tube densimeter is recognized as one of the most accurate methods,which bases on the relationship of system mass with mechanical vibration frequency.A direct-driven apparatus for density measurement is present.The material and dimension parameters of the U shape tube were determined.Permanent magnet was used to provide the magnetic field and the vibration characteristics of the U shape tube was experimentally studied.The structure of the apparatus was optimized.A thermosatic system and a pressure system were designed and experiments showed that the stability of thermostatic system is better than ±10mK in the temperature range from 303.15 K to 323.15 K and ±2.0% for pressure system at pressures from 0.1MPa to 20 MPa.Experiment was carried out to calibrated the instrument parameter and validate the performance of the vibrating tube densimeter.The data acquision system consists of a lock in amplifier and a function generator,which communicate with a computer via GPIB cables.The experimental data were collected and shown by DAQ software from Labview.Using pure water and ethanol as the reference fluid,the instrument parameters were obtained at temperatures from 303.15 K to 323.15 K and pressures from 0.1 MPa to 20 MPa.The density of isobutanol in the corresponding temperature and pressure range were measured and compared with literature data.The final results verified the feasibility of the vibrating tube densimeter.