| With the development of space precision measurement technology,the application of various high-precision instruments on spacecraft is increasing.In order to ensure the high-performance instrument performance,high-precision temperature monitoring and control methods are often used to maintain the stability of the temperature environment of the instrument.At present,the temperature measurement and temperature control accuracy requirements of some precision instruments have reached the mK level.Because of its high stability and good linearity,temperature sensitive platinum resistance is the most commonly used high-precision temperature measurement sensor.Resistance measurement is a key technology in platinum resistance temperature measurement system.In view of the above situation,this project will design a Pt1000 platinum resistance measuring instrument with equivalent temperature measurement accuracy of 1mK and normal operation in satellite variable temperature environment.In this paper,we analyzed the research status of platinum resistance measurement technology at home and abroad.The effects of lead resistance,thermo-electromotive force,circuit leakage current,measurement noise and temperature drift on the measurement accuracy are considered in detail.A suitable high-precision platinum resistance measurement scheme under the satellite change environment temperature is proposed.And we developed a resistance measurement system that can measure the Pt1000 platinum resistance to 3.9ppm under variable temperature environment.The main research contents of this paper are as follows:1.For the problem that the measurement accuracy in the traditional resistance measurement system is difficult to reach the required index,this paper first analyzes and compares the various resistance measurement principles and establishes the proportional method.The structural model of the proportional method resistance measurement system is established and the error analysis of the system is completed.The structure of the partial pressure ratio is proposed to realize the further optimization of the system.The signal acquisition module with peak-to-peak noise below 2ppm and the design and development of low-noise excitation structure with peak-to-peak noise less than 2ppm are realized.The final completed system has a noise peak-to-peak value of less than 3.9 ppm when measuring resistance,which can meet the requirements of the requirement.2.For the resistance measurement system working in the variable temperature environment where the satellite is working,due to the drift of the measurement result caused by the temperature drift of the system,the system temperature drift model is established and the temperature drift characteristics of each module are analyzed to determine the system.The main source of temperature drift is the reference resistor.By measuring the temperature drift characteristics of the system,the temperature drift law is obtained.A method of temperature self-test-software fitting correction is proposed to realize the compensation of system temperature drift.When the final measurement system is operated within the operating temperature range of 10 ° C to 40 ° C,the error due to its own temperature drift is less than 3.9 ppm.3.Combined with the above design,a complete high-precision resistance measurement system was developed.At the same time,a Pt1000 simulation device based on high stability resistance combination was designed,and the comparison of system measurement accuracy was carried out with the super thermometer as the reference.The experimental results show that when the system operates in the temperature range of 10 ° C to 40 ° C,and measure the resistance in the range of 833 Ω to 1250 Ω(equivalent to Pt1000 measurement temperature range-42 ° C to 65° C),the resistance measurement accuracy is 3.9ppm compared with the super thermometer as the reference. |
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