Design Of RTD Data Acquisition System For Temperature Measurement

With the advancement of manufacturing technology and the development of precision testing technology,accurate ambient temperature measurement plays a vital role in control engineering and process engineering.In high precision industries such as aerospace and semiconductor,in order to adapt to the measurement scenarios,RTD data acquisition systems for temperature measurement are required to have high precision,small size and good stability.In the complex wind tunnel test environment,the system needs to meet the requirements of high accuracy,small size and practicality at the same time.The RTD measurement circuit and data processing scheme are improved to design a high accuracy and small size RTD data acquisition system for temperature measurement with display and storage function for the wind tunnel test cavity temperature measurement requirements.The functional and performance requirements of the system are determined for the application context of wind tunnel experiments,the resistive temperature measurement scheme is studied and the characteristics of the common temperature measurement methods of RTDs are analyzed.The measurement scheme is improved by the dynamic proportional measurement method in the context of the application of this design,and the measurement error of the long-wire effect is controlled by using the four-wire connection technology and the hardware platform of RTD data acquisition system based on the resistance ratio is designed.Programmable triple-operating amplifier for instrumentation is adopted in the circuit,which effectively improves the common mode rejection capability of the system.The 24-bit high-resolution analog-to-digital converter is used to realize the high-precision and multi-channel sampling conversion function.The hierarchy of the system software is divided by the actual needs of the system.Based on AC excitation measurement method,the idea of three-point delta measurement method is used to improve the measurement data processing method and reduce the influence caused by the thermal potential.Pauta criterion and the mean value algorithm are used in the software for digital filtering to reduce the random error,and the fitting correction algorithm is designed based on the least squares method to eliminate the system error.The ARM chip driver and communication interaction application are designed and implemented to form the complete test system software.According to the temperature measurement principle of RTD,a standard resistor,a high-precision resistance box and a digital multimeter are used to build a system test platform to operate the temperature measurement system testing.The designed system has an error of less than 0.19 Ω in the range of 1000 Ω to 1385.06 Ω,and the error is less than 0.05 ℃ in the range of 0 ℃ to 100 ℃ for the standard RTD which can meet the fullscale precision requirement of 0.05%FS.The volume of the designed system is less than100mm×100mm×50mm,which meets the miniaturization index requirement.The comprehensive design and realization of the system’s performance index,as well as the measurement display,graphical and storage functions,the designed system can meet the designed system can meet the demand of cavity temperature measurement in the wind tunnel test of aircraft.