Research On The Rapid Detection System Of Field Soil Electrical Conductivity

Soil electrical conductivity is an important parameter of the soil environment and can be used as an important data for evaluating soil fertility and productivity and formulating precise fertilization prescriptions.This paper designs a vehicle-mounted field soil conductivity rapid detection and acquisition system based on the basic principle of the"four-terminal method",and gives a complete set of design schemes.Hardware design,software design,sensor production and experimental research are carried out around the core functions of the system.The main contents and results are as follows:(1)The measurement principle and the overall design plan are proposed.The research progress of soil conductivity detection systems at home and abroad is analyzed,and the principle of"AC four-terminal method"is selected as the basic principle of the system.The mechanical structure of the sensor,the digital AC constant current signal source,the conductivity signal detection and conditioning circuit and other related are completed.The hardware design of the data acquisition circuit.The software part is based on the system hardware,and the embedded system of constant current signal source,conductivity signal detection and multi-parameter integration embedded system and host computer are designed.Among them,the embedded system of the constant current signal source adopts pure digital control mode,the current output range is0～1000μA,the frequency range is 2～700Hz,and real-time feedback can be carried out according to the actual output current;conductivity signal detection and multi-parameter integration of the main functions of the embedded system It is the soil conductivity signal detection record,GNSS data reading record and ground surface temperature reading record.(2)Establish a prediction model for the conductivity of the soil solution.The various factors affecting the detection of the"four-terminal method"were analyzed,and a laboratory test bench was designed to simulate the working environment of the field.In the laboratory,610μS/cm,842μS/cm,1116μS/cm,1326μS/cm and 1597μS/cm,five kinds of soils with different soil solution conductivity,a four-factor five-level central combination experiment was designed,and a regression model of"soil conductivity-soil moisture content-electrode penetration depth-temperature"and sensor signals was obtained,which was used to predict soil Solution conductivity,under laboratory conditions,the model R~2 is 0.9975,and the predicted R~2 is 0.9961.(3)Field test.The stability and repeatability of the field soil conductivity rapid detection system is verified in the actual work scenario.When the detection path is close,the original signal of the detection system sensor has the same linear trend,and the average difference is less than 15%of the detection average.In the field verification test,the prediction value of the detection system is consistent with the actual value of the field soil solution conductivity,which can effectively predict the distribution of soil solution conductivity in the field and provide a reference for subsequent precise fertilization operations.