Measurement of Liquid Nitrogen Mass in Dewar by Radio Frequency

With the wide application of liquid nitrogen in industrial manufacturing, liquid nitrogen metering based on dewar has become a focus of attention in the industry. In the past, the metrology of liquid nitrogen still remained at the stage of liquid level measurement, and no extensive research has appeared for the accurate measurement of liquid nitrogen quality. In this paper, for the measurement of liquid nitrogen quality inside dewar, an experimental system is built based on RFMG technology. Vector network analyzer with faster sweep is used to measure the return loss of the port, and the principle of this technology for liquid nitrogen quality measurement are analyzed. A numerical model of resonance frequency and liquid nitrogen filling ratio is established by simulation calculation, and then the numerical model is compared with the experimental data. It is found that the nonlinear error between the measured value of this technology and the simulated numerical model is 1.4%. RFMG has a broad prospect in the industrial application of liquid nitrogen, and it can realize the accurate measurement of the quality of liquid nitrogen in the dewar in the place of the traditional liquid level meter.