The Design Of A Measuring Device For Low Temperature System Of High Temperature Superconducting Maglev Vehicle

The liquid level of liquid nitrogen in low temperature system of high temperature superconducting maglev vehicle must be detected at real-time to ensure that high temperature superconducting maglev vehicle keeps safe running When high temperature superconducting maglev vehicle is running.As the limit of dewar and stong magnetic field, none of sensor of liquid level on market can measure liquid level of liquid nitrogen. Therefor thin film platinum resistance temperature sensor PtlOO is choosen to measure liquid level of liquid nitrogen indirectly in the way of measuring temperature.Utilizing the characteristic of temperature sensor that resistance of temperature sensor varier with temperature, supplying constant current driving and measuring the voltage of each RTD to obtain the resistance, then calculating the temperature of this point where this RTD is located. By multi poind temperature measuring, finanly, ascertaining the liquid level of liquid nitrogen in dewa.The hardware circuit of this device is composed of precision constant current which is made up by operational amplifier ICL7650, sensor of liquid level of liquid nitrogen which is constitued by PtlOO, 48 channels differential multiplexers which is made up by CD4067, voltage amplifying circuit and core module based on μPSD3251,etc.Core module is constitued by LED displaying module, RS232 communication molule, digital filtering modual and liquid level calculating module,etc. Ultimately,the device implements measuring for liquid level of liquid nitrogen, data displaying and series data sending.By installing and debugging, this device successfully implements autoreal-time detecting for low temperature system of high temperature superconducting maglev vehicle.The result of experimentation indicate that this device's precision is -4mm~+1mm with high reliability, strong mobility,high speed, easy extending and high cost performance. It meet the demand of measuring for low temperature system of high temperature superconductingmaglev vehicle. This device even can be used to measure liquid hydrogen, liquid oxygen, etc low temperature liquid and oil liquid.There is still some improvement in need of in the design, for instance, simplifying analog signal processing circuit, supplying with sigle power,enhancing integration,utilizing ADC with stronger resolution ,etc.This devie can be came into being as a kind of new type product for low temperature liquid level measuring by more optimize design.