Design And Implementation Of High-precision Layered Temperature Measurement Device

During the flight test,the measurement of the temperature data of the inner side wall and the outsole of the test cabin can obtain the temperature of the surface heat-resistant structure at different depths,which is of great significance to the thermal protection work and the safety of the entire system test.Considering the complex electromagnetic environment in the test cabin,and the temperature variation in different parts of the cabin is quite different,so higher accuracy and reliability of the temperature measurement device are required.This paper studies and designs a high-precision layered temperature measurement device,The number of temperature measurement channels is 4,You can select a thermocouple or platinum resistance for temperature measurement according to the size of the temperature measurement range,The temperature signal is transformed,conditioned,collected and coded,and the sampling data is uploaded to a host computer or a telemetry device for analysis.First of all,combined with the research status of temperature acquisition at home and abroad and the use of equipment,the data transmission mode and sampling method were determined,and an overall design scheme was proposed.According to the temperature measurement range of different channels,S-type,K-type thermocouples and platinum resistance pt1000 are selected as temperature-sensitive components.According to the difference between the thermocouple temperature measurement characteristics and the graduation number,two cold circuit compensation hardware circuits with AD8495 and AD590 as the core are designed.The comparison and selection of compensation wires are also introduced to improve the equipment's adaptability to ambient temperature;According to the principle of platinum resistance temperature measurement,through analysis of its driving methods,a high-precision constant current source driven four-wire temperature measurement method is proposed and designed,the design and analysis of the key technology constant current sources are compared and optimized.It can effectively remove the influence of its own line resistance and reduce the self-heating effect,and improve the measurement accuracy.For improving the anti-interference ability of the equipment to complex electromagnetic environment,the gain adjustment is adopted in a differential manner,and filtering design is added,including RF radio frequency filtering,second-order voltage-controlled low-pass filtering,the purpose is to filter out radio frequency interference in the environment and the line transmission Crosstalk.In terms of acquisition and quantization,in view of the characteristics of low sampling frequency of temperature signals and high requirements for acquisition accuracy,a ?-? ADC is used for analog-to-digital conversion.This article introduces the oversampling,digital decimation filtering,and noise shaping techniques applied by the ?-? ADC and analyze its high-resolution and low-noise sampling mechanism.Adopt dual timer program design to optimize timing logic of analog switch switching,A/D conversion and serial communication to achieve uniform sampling and unified data framing and forwarding,And by analyzing and verifying the effect of the selection of the decimation filter and the decimation ratio on the acquisition accuracy,high-precision signal acquisition is achieved.By building a test platform,the temperature measurement device was tested comp-rehensively,and the reliability and measurement accuracy of the device were analyzed and summarized to verify the feasibility of the design.