Design And Implementation Of Multi-channel Thermocouple Temperature Measuring System

With the pace of deep space exploration picking up gradually in our country,more and more spacecraft need to be sent to space to work,and spacecraft in the process of flight to heaven and earth encounter the greatest heat flux can reach 420 solar constants,the temperature can reach a maximum of 1600℃,and spacecraft will be exposed to the vacuum environment after entering preset orbit.The side exposed to the sun can reach 100℃,while the temperature of the side with the back sun can be as low as-200℃～-100℃.Therefore,facing such a complex external environment with such a large temperature change,it is necessary for spacecraft to conduct vacuum thermal tests on the ground for different space products and components before launching.According to the above background,this paper designs a multi-channel thermocouple temperature measuring system for vacuum thermal test of spacecraft.In terms of hardware,according to the design requirements,S,K and T thermocouples are selected as temperature sensing components,corresponding to the characteristics and differences of each thermocouple.Two kinds of cold end compensation schemes are used: MAX31856 internal cold end temperature sensor and AD597 special cold end compensation chip.In view of the requirement of high acquisition accuracy,Σ-Δ ADC is used to design the temperature acquisition module,and a filter is designed to remove the interference of the environment in the process of data acquisition and transmission.In order to improve the anti-interference ability of the equipment facing the complex electromagnetic environment,the electromagnetic shielding design is carried out when PCB is drawn.In programming,the Field Programmable Gate Array(FPGA)internal large number of lookup tables,RAM resources and rich wiring resources are utilized to achieve multi-channel data collection and transmission.At the same time,SCM is used to realize the storage of measured temperature data and the sliding average filtering processing,and the calculated temperature data is transmitted through the serial port to the supreme computer for display;In this paper,the combination of FPGA and single chip microcomputer as the core control unit can better solve the conflict between resource possession and algorithm processing,there are sufficient resources to improve the speed and accuracy of data processing.The test results show that the multi-channel distributed thermocouple temperature measuring system designed in this paper can realize the measurement of 16-channel T,K or S thermocouple temperature signals,the measurement range can reach-20℃～1600℃,and the temperature curve can be drawn through the upper computer.The relative error is lower than the designed ± 0.5% F.S.In addition,by comparing the relative error between different channels under the same type of thermocouple,the consistency and accuracy of measurement results between channels are verified.