民勤沙区非称量式蒸渗仪组扩容及其自动化监控系统设计

Capacity expanding in non-weighed Lysimete and its automatic monitoring and control system in Minqin desert area

为解决民勤沙区非称量式蒸渗仪观测系统自动化程度低、尺度扩展性不足及可靠性差等问题,建立民勤沙区非称量蒸渗仪试验场720 m^2,更新改造30个荒漠植物个体蒸渗仪,扩容建造12个荒漠植物小群体蒸渗仪,设计非称量式蒸渗仪自动化监控系统,该系统采用分布式监控方案,以上位工控机为中心,基于智能仪表(RS485总线通讯、ISM无线)、ISM频段无线通信及TCP/IP网络协议,布设了多个下位机监控点,可自动控制蒸渗仪恒定水位,能及时补水、排水并进行水量计算,自动监测蒸渗仪土壤水分含量,同时具备实时数据采集与处理、信息通信、数据库录入、历史数据存储、数据报表打印、故障报警、现场设备运行状况显示等功能,用户可通过因特网对现场设备工作状态进行远程监控、异常情况报警处理。系统测试得到,压力传感器数据回归分析误差±2.2%,点滴计数器为±2.0%,水分传感器±12.5%。该研究扩展了荒漠植物定位观测的尺度范围,实现了荒漠植物蒸渗观测的自动化监控,为荒漠植物蒸渗研究提供可靠的试验平台。

The non-weighing lysimeter system in the Minqin desert areas was firstly used in the 1970 s, and mainly performed the orientation research on the water consumption by the transpiration of several desert plants and the evaporation on the surface of sand, which aimed to provide the theoretical guide for the selection of afforestation density and the utilization of sand and water in Chinese sand areas. At present the system has been running for 30 years, most of the lysimeters showed the jam and leakage phenomenon, and the observation was by conventional artificial means. All the factors seriously affected the accuracy of the data monitoring. However, on the basis of the non-weighing lysimeter system structure and its testing principle, the evapotranspiration area could be extended, the capacity of testing soil column could be increased, more real natural environment conditions could be simulated and the limitations of weighing lysimeter could be overcome, in sum, the lysimeter’s application field and adaptability were extended. Owing to the problems of low automation, and lack of scalability and reliability, the non-weighed lysimeter monitoring and control system in the Minqin desert areas has been retrofitted to improve its performance based on structure characteristics. The non-weighed lysimeter proving ground of 720 m2 was designed in Minqin sand areas, where 30 individual lysimeters (120 cm×120 cm) of desert plant were upgraded and 12 small groups of desert plant lysimeters (400 cm×400 cm) were expanded and built, at the same time, the lysimeter groups in different types could be used to carry out the test of water supply for plant under the constant water level of 190, 290 and 390 cm. The lysimeter proving ground upgraded and expanding-built could realize synchronous observation for evapotranspiration test from the desert plant individual scale to small group scale, and the experiment platform was provided for studying water consumption of desert plants transpiration in different scale and its coupling relationship. The distributed monitoring scheme was adopted in the new automatic monitoring system, in which the superior industrial computer was set up as the center with multiple lower machine monitoring points, such as lysimeter constant water level control and water-supplying measurement system, drainage measurement system, atmospheric precipitation monitoring system, soil moisture monitoring system, environment temperature measurement and control system, SMS cat alarm system, data remote transmission and monitoring system, and UPS over-voltage protection system, and the RS485 bus, ISM wireless communication and TCP/IP network structure were used in the system. The automatic control of the lysimeter water level, water supply and drainage, the automatic monitoring of water metering, and the soil water content were designed, and the atmospheric rainfall and the temperature indoor were monitored in real time in the new system; the system also had the functions of real-time data collection and processing, information communication and data entering, historical data storage, data report printing and remote transmission download, and the power supply system was protected against over-voltage to enhance the reliability of system operation and the stability of data acquisition. Additionally, the internet-based remote monitoring and control system was used, and the users could process the abnormal situation. According to the monitoring data analysis by the regression method, we could know that the errors of data regression analysis were ±2.2% for the pressure sensor, ±2.0% for the drop counter and ±12.5% for the moisture sensors. The research extended the scale for locating observation of the desert plant and implemented the automatic monitoring for evapotranspiration of the desert plant.