Numerical and experimental investigation on NbTi superconducting liquid helium level sensor based on a resistance heating

A resistance-heated NbTi superconducting liquid helium level sensor based on the principle of thermal conduction is proposed. A heat transfer model for the sensor was established, and its mathematical model was characterized. The effects of temperature, current, heating resistance value, and superconducting wire diameter on the sensor performance were investigated. It indicates that the temperature of the sensor in the vapor phase is decreased linearly from high to low, and the voltage is decreased with the increase of the liquid level. And the 45 μm diameter superconducting wire has a minimum propagation current, a minimal heat input to the system, and a small measurement error. The variation of the sensor output voltage with a level height was studied experimentally. The linear correlation coefficients R2 of the 1 Ω, 5.1 Ω, and 10 Ω sensors are all greater than 0.999, which are almost identical to the simulation results. The sensor’s response time is all less than 1s, the sensitivity is 8.7070mV/mm, 8.0110mV/mm, and 6.9660mV/mm, respectively, and the accuracy is 0.8226%, 0.8611%, and 0.9030%.