LIQUID-NITROGEN DETECTING ELEMENT AND LIQUID NITROGEN DETECTOR

摘要

PURPOSE:To make it possible to perform very stable operation and to improve reliability, by utilizing transition between superconductivity and normal conductivity, and detecting discontinuous change in resistance value. CONSTITUTION:A main body part, which comprises a material having the transition temperature of superconductivity within the range of nitrogen liquefaction temperature of -147.1--195.8 deg.C, is provided. Terminal parts for electrical connection are provided. The inside of a Dewar flask 4 is filled with liquid nitrogen 6. Then, the liquid level rises up, and a detecting element 3 is immersed in the liquid nitrogen. The normal conducting state of the element is changed into the superconducting state, and the resistance value of the element is decreased. Therefore, a voltage across an output resistor 5 is changed, and an output voltage is yielded in an amplifier 2. In this way, the liquid level of the liquid nitrogen is detected. In order to make the transition possible, it is practical that the superconductivity transition temperature of the main body of the detecting element is made to be -141.7--195.8 deg.C, which is the temperature where nitrogen is liquefied.