Study On A Practical Johnson Noise Thermometer System

As the basic unit of temperature in thermodynamics’ measurement,the value of kelvin will be changed based on the magnitude of Boltzmann constant accordingly.And the Johnson noise thermometer which can be able to measure both Boltzmann constant and thermodynamics’ temperature is a significant method.Develop a high-performance Johnson noise thermometer to measure thermodynamics’ temperature not merely have reference value to the continuous development of the international scale and it will take up a wide development prospect in industry,national defense and other fields.Based on a quantum voltage calibrated Johnson noise thermometer,a practical Johnson noise thermometer is developed.It consists of fixed points,resistance used for temperature detection,amplifier,analog-to-digital conversion circuit and filter circuit,a digital correlator and so on.It is discussed that the working principle of the system,the hardware and software’s build plan and implementation process of the core device in the paper.In this paper,the main research work is as follows:1.Design a 200 Ω high-precision fixed resistor used in-50~200℃ and its protection device is fabricated.The pricision of the resistor is 71.0 10-′ and The temperature coefficient is 64 10-′(1/K).Its resistance which is measured so many times can be stable in 5 ppm.And all of the data are concluded by experiments.2.A digital correlator is introduced.It consists of MCU processor EP4CE6E22C8 N,USB2.0 interface chip CY7C68013 A,High-speed optical transmitter and receiver HFBR-2526/1527,analog to digital conversion circuit and so on.3.Kinds of program are designed in the paper,for example,the control program of the correlator,USB firmware program,the drivers of the interface and PC program based on LabVIEW.By the hardware and software,the correlator realizes the collection of data.And the test data transmission speed can reach 27 MB/s.4.A practical Johnson noise thermometer is built and We calibrate it by quantum voltage.The result show that the different value between calibration and theory is 2.1466 mK with a random error 7.85 ppm.And the two channels’ standard combined uncertainty is 11.32uK/K.5.Gallium point’s temperature is measured by the practical Johnson noise thermometer.When measured,the noise is compared with quantum voltage and the noise of resistor maintained at the triple point of water.The result show that the different value between measurement and theory is 6.5447 mK with a random error 21.6ppm compared with quantum voltage.Meanwhile,the different value between measurement and theory is 9.97 mK with a random error 36.5ppm compared with the noise of resistor maintained at the triple point of water.6.Improve hardware circuit of the system and we achieved a 10KHz~600KHz frequency bandwidth which is 10KHz~50KHz in the past.Moreover,the measuring time reduced by 190h to 12h.