Development of a magnetic single-sinker densimeter based on direct displacement regulation over a wide temperature range from 85 to 350 K and pressures up to 15 MPa.

A magnetic-suspension single-sinker densimeter was developed for refrigerants over a broad temperature range (85–350 K) and at pressures up to 15 MPa. The densimeter incorporates adjustable temperature-synchronized cold shields and an innovative direct displacement regulation method that sets predefined displacement parameters to dynamically regulate the electronic magnet current. This approach ensures sinker stability through controlled current adjustments, significantly enhancing operational efficiency and adaptability across diverse fluids and temperature conditions. A segmented range approach was employed for temperature regulation with uncertainties of ±0.1 K (85–150 K), ±0.05 K (150–290 K), and ±0.01 K (290–350 K). When validated against NIST REFPROP 10.0 using R290, nitrogen, and argon as specimens, the system achieved a maximum absolute relative deviation in liquid density of within 0.6 % across all temperatures.