T-TDR传感器热电偶结点位置优化试验

Optimization Experiment of T-TDR Sensor Thermocouple Node Positions

摘要:

为提高T-TDR（Thermal-time domain reflectance）土壤水分传感器的测量准确度，优化传感器的结构参数，对比研究了热电偶结点嵌入位置和大小对T-TDR传感器热特性敏感度和测量精度的影响规律。设计热电偶结点分别在探针中点和中点下移2mm处的位置，通过点焊方式减小热电偶结点体积，制作出3种类型的T-TDR传感器及其测定系统。分别在砂土、砂质壤土、粘壤土的5种不同含水率条件下对3种传感器进行热特性试验，测定其热特性曲线并计算含水率，利用干燥法进行精度检验。结果表明，热电偶在中点位置下移2mm及采用点焊方式小结点的传感器对中间探针的辐射热量较其他两类传感器敏感，灵敏度也较高，含水量测定结果与干燥法测量值有较好的相关性（R 2 为0.981，RMSE为0.0152），测量精度比传统结构参数的传感器有所提高。

Abstract:

In order to improve the measurement accuracy of T-TDR sensor and optimize its structure parameters, the rules of the thermocouple node embedded positions and size to its sensitivity and accuracy were studied. Based on the node in the probe middle, midpoint moving down 2mm and reducing the volume thermocouple nodes by spot welding, three kinds of T-TDR sensors and their measuring system were designed. The five different water content of each sandy, sandy loam and clay loam were tested to measure the thermal characteristic curves and calculate its water content. Oven drying method was used to test accuracy. The results showed that the thermocouple on the probe midpoint moving down 2mm and spot welding junction was more sensitive to the radiant heat of the 〖JP3〗intermediate probe than the other sensors. The measurement value of moisture content had good correlation (R2 of 0.981, RMSE of 0.0152) between drying method. The measurement accuracy was higher than traditional structural parameters.