Measurement of soil electrical conductivity based on direct digital synthesizer(DDS)and digital oscilloscope  

作　　者：Xiaoshuai Pei Chao Meng Minzan Li Wei Yang Peng Zhou 

机构地区：[1]Key Laboratory of Modern Precision Agriculture System Integration Research,Ministry of Education,China Agricultural University,Beijing 100083,China [2]Key Laboratory of Agricultural Information Acquisition Technology,Ministry of Agriculture and Rural Affairs,China Agricultural University,Beijing 100083,China

出　　处：《International Journal of Agricultural and Biological Engineering》2019年第6期162-168,共7页国际农业与生物工程学报（英文）

基　　金：This study was supported by the Chinese National Key Research and Development Plan(2016YFD0700300-2016YFD0700304);the National Natural Science Foundation of China(31801265).

摘　　要：A soil electrical conductivity(EC)measurement system based on direct digital synthesizer(DDS)and digital oscilloscope was developed.The system took the“current-voltage four-electrode method”as the design principal and adopted a six-pin structure of the probe,two center pins to measure the soil EC in shallow layer,two outside pins to measure the soil EC in deep layer,and two middle pins for inputting the driving current.A signal generating circuit using DDS technology was adopted to generate sine signals,which was connected with the two middle pins.A digital oscilloscope was used to record and store the two soil output signals with noises in microseconds,which were from the two center pins and two outside pins,respectively.Then a digital bandpass filter was used to filter the soil output signals recorded by the digital oscilloscope.Compared with the traditional analog filter circuit,the digital filter could filter out the noises of all frequency except for the frequency of the excitation source.It could improve the effect of filtering and the accuracy of the soil EC measurement system.The DDS circuit could provide more stable sine signals with larger amplitudes.The use of digital oscilloscope enables us to analyze the soil output signals in microseconds and measure the soil EC more accurately.The new soil EC measurement system based on DDS and digital oscilloscope can provide a new effective tool for soil sensing in precision agriculture.

关 键 词：soil electrical conductivity direct digital synthesizer digital oscilloscope precision agriculture current-voltage four-electrode method 

分 类 号：TN7[电子电信—电路与系统]