A continuous level-indicator for liquid helium

In most cases of work involving liquid helium, continuous monitoring of the liquid level is a basic requirement. Conventional liquid-level indicators suffer from a number of defects - innaccurate detection, limitations as to permissible ambient conditions, complexity of calibration, and the fact that the detecting element cannot be replaced - which make such indicators unsatisfactory for industrial application. A new continuous level indicator without these defects has been constructed using a detecting element of Nb-Ti wires having the extremely small resistivity ratios of rho300K/rho10K=1.07 and rho10K/rho77K=0.975. Standard specifications of the element are: measuring length 400mm, outside diameter 5mm, weight 20g, and a heat loss in liquid helium of zero and in gaseous helium of 0.02 W/cm. (auth.)