电容液位计测量液氮气瓶液位的实验研究

Experimental study of capacitance liquid level gauge for measurement of level in liquid nitrogen cylinder

为了探究电容式液位计在液氮绝热气瓶液位测量中的精度及相对误差变化规律,利用单电容和三电容液位计进行液位测量实验,并与称重实验进行对比验证。结果显示:单电容和三电容液位计的相对误差分别为4.9%和1.9%,单电容液位计相比目前应用的圆筒电容液位计平均测量精度已提升了5%左右,三电容液位计测量精度较单电容提高3%。从信号变送器的设计方面分析精度提高的原因为三电容液位计对液氮介电常数进行了精确修正,探究得到电容液位计相对误差的变化规律及原因。实验中使用的电容液位计还可用于液氢、液氧以及液化天然气等低温容器的液位测量中,能够促进低温液体在各领域中的应用推广。

In order to explore the accuracy and relative error variation of the capacitive level gauge in liquid nitrogen adiabatic cylinder level measurement, the single capacitor and three-capacitance level gauge are used to carry out liquid level measurement experiments, and the comparative verification with the weighing experiment is conducted. The results show that the relative errors of single capacitor and three-capacitor liquid level gauges are 4.9% and 1.9% respectively. Compared with the cylindrical capacitor liquid level gauge, the average measurement accuracy of the single capacitor liquid level gauge has been improved by about 5% and that of three-capacitors liquid level gauge has been improved by 3% in comparation with the single capacitor liquid level gauge. The reason for improving the accuracy of signal transmitter design is that the dielectric constant of liquid nitrogen is corrected accurately by the three-capacitor level gauge. At the same time, the change rule and reason of relative error of the capacitive level gauge are obtained by exploration. The capacitive level gauge used in the experiment can also be used for the liquid level measurement for cryogenic vessels such as liquid hydrogen, liquid oxygen, liquefied natural gas, etc., and can promote the popularization and application of cryogenic liquid in various fields.