基于LXI总线的热电偶采集系统设计与应用验证

Design and Application Verification of Thermocouple Acquisition System Based on LXI Bus

摘要:

针对复杂装备测试时多通道热电偶传感器的高精度高稳定性温度测试需求,设计了一种基于LXI总线的热电偶采集系统,单台设备具有48个测量通道,通过LXI总线可以实现多设备间同步测量,大幅提高了测量效率与测量精度。本系统采用高精度24位模数信号采集与调理技术,电压采集分辨率最小可达到0.032uV、温度采集分辨率达到0.04℃,电压测量精度达到0.05%；设计了一种高精度快速冷端温度补偿模块,可以有效补偿环境温度变化所带来的测量误差,T型热电偶温度测量精度达到0.25℃；集成了多种热电偶传感器电压-温度信号转换与补偿算法,支持J、K、T、E、S、R、B、N型8种热电偶；为有效解决数百通道温度采集面临的多设备同步采集问题,采用了LXI总线架构,多设备间均通过LAN进行数据通讯。为进一步验证所设计系统的性能,通过某计量实验室进行了温度准确度与电压准确度测试,R型热电偶温度测量误差在0.45℃内、S型热电偶温度测量误差在0.6℃内；最后,在某发动机综合测试试验台上进行了K型热电偶实测验证,并通过与NI公司的PXIe-4353模块进行对比测试,验证了所设计的热电偶采集系统具备较高的测量精度,K型热电偶准确度达到了0.5℃。

Abstract:

Aiming at the requirements of high-precision and high-stability temperature testing of multi-channel thermocouple sensors in complex equipment testing, this paper designs a thermocouple acquisition system based on LXI bus. And the single device has 48 measurement channels. Synchronous measurement between multiple devices can be realized through the LXI bus, which greatly improves the measurement efficiency and measurement accuracy. The system adopts high-precision 24-bit analog-to-digital signal acquisition and conditioning technology, so that the voltage acquisition resolution can reach 0.032uV, and the temperature acquisition resolution can reach 0.04°C, and the voltage measurement accuracy can reach 0.05%. A high-precision fast cold junction temperature compensation module is designed, which can effectively compensate for the measurement error caused by ambient temperature changes, and the temperature measurement accuracy of T-type thermocouple reaches 0.25°C. The voltage-temperature signal conversion and compensation algorithms of various thermocouple sensors are integrated into the system, which can support temperature measurement of eight thermocouple types of J, K, T, E, S, R, B, and N. In order to effectively solve the synchronous acquisition problem between multiple devices faced by hundreds of channels of temperature acquisition, the system adopts the LXI bus architecture, and the data communication between multiple devices is carried out through LAN. In order to further verify the performance of the designed system, a temperature accuracy and voltage accuracy test was carried out by a metrology laboratory, and the results showed that the temperature measurement error of R-type thermocouple was 0.45°C and that of S-type thermocouple was 0.6°C. Finally, the K-type thermocouple was verified on a comprehensive engine test bench, and the comparison test with NI"s PXIe-4353 module was passed. It is verified that the designed thermocouple acquisition system has high measurement accuracy, and the measurement accuracy of K-type thermocouple reaches 0.5°C.