过去已经有几种或多或少比较复杂的装置,用来监测杜瓦中的液氦液面。一种不需象震动管那样具有判断力,但能实现相同功能的简单,便宜装置是需要的。长期以来,许多实验室都已用了碳电阻插入液氦,监测其电阻值 There have been several more or less complex devices in the past for monitoring the liquid helium level in Dewar. A simple, inexpensive device that does not require the same judgments as a vibrating tube but achieves the same function is desirable. For many years, many laboratories have used carbon resistors to insert liquid helium to monitor their resistance