High accuracy fluid PVT measurement system based on magnetic suspension densimeter

A fluid PVT measurement system based on magnetic suspension densimeter was developed. The temperature range is 20315~42315 K with standard uncertainty of 0005 K, and the pressure range is 0~70 MPa with standard uncertainty of 700 Pa. The temperature control system was modified, thus the time reaching equilibrium state was shortened and the temperature stability was improved. The developed PVT system was used to measure the density of high purity nitrogen at 271~345 K, 0~6 MPa, and the average absolute deviation between experimental results and the NIST REFPROP90 data was within 01%, and the density uncertainties due to the uncertainties of fitted virial equation and measured temperature and pressure was analyzed.