The Research And Design Of Automatic Water Measuring System On The Open Channel In Farmland Irrigation District

With the rapid growth of global demand for water resources and the water pollution because of environmental deterioration, water resources crisis becomes more intensified. Our country is a country with severe water shortages, and agricultural irrigation water accounts for more than60%of water resources. As the traditional water measuring methods cause a lot of waste of water resource, to save water resource and realize "using water according to plan and charging according to water quantity", there is need to accurately measure the irrigation water.On the basis of the analysis on the development process, the current research and today’s practical application of water measuring technology of irrigation district, this paper studied and designed a set of automatic water measuring system on the open channel in farmland irrigation district.The automatic water measuring system adopts the flow measuring method based on.flume, selects the airfoil-shaped flume as the basic measuring unit, uses the self-developed millimeter digital water level sensor to measure the water level signal of the flume’s upper river which is sent to the host computer monitoring system for processing and calculates the flume’s flow according to the corresponding function of water level and flow, thus reaching the purpose of flow measurement. According to the design thought, this paper completed the following work:(1) developed millimeter digital water level sensor autonomouslyAccording to the basic principle that irrigation water can conduct electricity, each part of the hardware circuit of water level sensor was designed.①Circuit of main controller and power supply module:the core chip are respectively MSP430F149and LM1117-3.3;②Circuit of signal acquisition part:including detecting circuit, voltage comparison circuit with the LM339as the core chip and a multi-channel selecting circuit with the ADG732as the core chip;③the display circuit:using three digital tube to display water level value;④the communication interface circuit:using the electric level conversion chip MAX3232to design the serial communication for the data transmission with PC.On the basis of every part of hardware circuit, the lower computer software was programmed using the C language and the modular design method, realizing the function of water level sensor. The water level sensor has the following advantages:high accuracy; low power consumption; high integration; digital acquisition and transmission of water level signal as well as high stability and reliability.(2)Design the upper computer’s monitoring software The upper computer’s monitoring software programmed by using Visual Basic6.0language can monitor the water level signal, get flow information by analyzing and processing the data and realize the following functions: calculating the flow of a variety of types of sections by inputting calculation formulas of flow of various sections of channels;②calculation of multi parameters, including water level, instantaneous flow and cumulative flow;③summarizing and storing the sum of water of the year, month and day.Finally, through the debugging test, it was proved that:the self-developed millimeter digital water level sensor operated pretty well, reaching the designed precision and displaying stably and reliably; the lower computer and PC communication was normal, which could realize monitoring by the computer and the designed function; the measured flow got relatively high precision and finally realized the automatic water measuring on open channel with a good application prospect.