Development of High Precision Level Gauge for Helium II

1.研制了一种氦Ⅱ超导连续液位计。传感元件采用锡（镀膜）与哈氏合金或分子合金（基体）的复合材料。通过溅射将锡涂覆在0.2[mm]的基板上。我们研究了三个因素的影响。（1）镀锡层的最佳涂覆深度。（2）最佳工作电流，以消除膜沸腾或爬升超流引起的误差。（3）工作电流的供给方式：为了提高测量精度，使超导体在正常状态下的电阻比哈氏合金或分子合金大得多。通过对镀锡层厚度和工作电流的选择，证实了所研制的液位计测量液位的精度在1[mm]以内。当锡的表面电阻为3.89[Ω/*]且操作电流为120[mA]时，获得最佳结果。精度在0.45[mm]以内。只有在测量完成时才提供工作电流。在此基础上，研制了一台样机.浮子式、超声波式和差压式液位计也经过了测试。浮子式压力计灵敏度过高，重复性差。超声波型测量仪需要太昂贵的电子设备。没有找到与差压计的低温和非常小的压差条件相匹配的合适材料。

1. A continuous level gauge using superconductor for helium II has been developed. Composite of tin (coated film) and hastelloy or moleculoy(substrate) were used as sensing elements. Tin was coated on substrate of 0.2[mm] by spattering. We have examined the effects of 3 factors.(1)the optimum coating depth of tin coating.(2)the optimum operating current to eliminate the error caused by film boiling or by climbing superfluid.(3)the mode of suppling the operating current to the gauge.To raise the accuracy of measurement, the electric resistance of the superconductor in normal state was made very large compared to that of hastelloy or moleculoy. By appropriate selections of coating depth of tin and operating current, it has been confirmed that the liquid level was measured with accuracy within 1[mm] by the level gauge developed. The best result was obtained when surface resistance of tin was 3.89[OMEGA/*] and the operating current was 120[mA]. The accuracy was within 0.45[mm]. The operating current was supplied only when the measurement was done. A proto-type level gauge was fabricated on the basis of these findings.2. Float-,ultrasonic- and differential pressure-type level gauges have been tested too. The float-type gauge showed poor reproducibility because of too high sensitivity. The ultrasonic-type gauge required too expensive electronics. Any appropriate material matching the condition of low temperature and very small pressure difference for a differential pressure gauge was not found.