LIQUID HE LEVEL DETECTING APPARATUS

PURPOSE:To monitor the surface of liquid He continuously, by automatically selecting only resistor elements at the upper part and the lower part of the liquid surface among a plurality of resistor elements, which are provided in an He container. CONSTITUTION:Resistor elements 7a-7g, which are provided in an He container 2, are connected to preamplifiers 4a and 4b through a measuring signal switching relay 12. Whether two resistor elements 7, which are performing measurement at present, are placed in a liquid He 6 or not is judged by temperature setting devices 10a and 10b through linearizers 8a and 8b. By using contact signals 13a and 13b, which are generated by the judged result, the switching relay 12 is controlled so that the two resistor elements to be measured are positioned on both sides of the level of the liquid He. Lamps 14 are turned ON and OFF by using the signals from the switching relay 12. Thus the surface of the liquid He can be continuously monitored.