低温液面测量用电容传感器的研制

The Development of a Capacitance Sensor Used in Cryogenic Liquid Level Measurement

本文介绍了电容式低温液面计的敏感元件——电容传感器的研制。对其工作原理、结构、实验和使用等方面做了叙述。电容传感器具有结构简单、体积较小、工作可靠、绝缘性能好、漏热小以及使用方便等优点。在内电极引出管中,增加了零位电容补偿线;在外电极与八芯密封插座之间,采用了导热系数小的尼龙材料做连接座。提高了电容传感器的性能,减小了探头上部漏热对液氦的损耗。

This article describes the development of a capacitance sensor used as a sensitive element cf a capacitive type crycgenic liquid level gauge. The cperation principle, the construction principle, the construction design, the test and the usage of it are described. The outer diameter of the sensor is 10 mm, measuring range-0～1000mm, insulance between electrodes-more than 20 megohm, liquid helium loss from heat leak of the sensor-less than ll/24h. The joint of octal scket and nylon connection can resist the vacuum of lx10^(-6) tcrr. The compensation wire for calibrating zero level is fitted in the leading tube of the inner electrode,so that the effect of distributed capacitance change of electrode leads to the measurement can be minimized. The connection between outer electrode and octal socket is made of nylon, which has low thermoconductivity. Therefore, the liquid helium loss from heat leak is reduced. After repeated tests it is proved that the structure is reasonable and the performance of the sensor is stable and reliable at 4.2 K. The error in liquid level measurement is±2% for helium and ±1% for nitrogen if the level is kept calm in Dewer. This has already met the requirements for continuous level measurements of liquid helium and nitrogen in cryogenic engineering and experiments.