Development Of Mul-fuctional Sensor Of Water Content And Electrical Conductivity

As the basis for the growth of crops, soil’s physical and chemical parametersdirectly affect crop’s yield and quality. With the rapid development of informationtechnology, modern agriculture is gradually to digital and precision development.Sensor technology is the perception of agriculture digital systems whose workingconditions directly affect the entire system. Sensors used for soil parametersusually measure a single parameter. While the soil is a highly complex system, therelationship among its various parameters influences each other. Developing asimultaneous multi-functional sensor of which all parameters are measured in thesame place is necessary.In this paper, through studying the main parameters of the soil which affectcrop growth, I select soil volumetric water content and electrical conductivity tomeasure. By comparing and analyzing all the measurement method of thevolumetric water content and electrical conductivity, I choose heat pulse methodand the current-voltage four-terminal method which is practical and low cost todesign the soil multi-functional sensor.Firstly, I studied the theory of heat pulse and simulated it by the softwarecalled Comsol. I was sure that the design of thick-probe structures could also beapplied to the theoretical calculation of heat pulse, and given temperaturemeasuring point in the best layout range. Secondly, I analyzed the theory of“current-voltage four-electrode”, stated the difference in the conductivitymeasurement using diverse electrode structures and ultimately selected the“Wenner” electrode distribution. Finally, I designed a measurement system for mysensor and debugged it to certify that this system can effectively obtain themeasurement data.Through the sensor’s calibration and sand experiment, I determined thestructural parameters of sensor. By comparing between measured data andtheoretical data, I indicate that this multi-functional sensor which measures soilvolumetric water content and electrical conductivity can meet the requirements.