Comparative Study of Two Soil Conductivity Meters Based on the Principle of Current-Voltage Four-Terminal Method

摘要

The measurement of soil conductivity is generally based on the theory of current-voltage four-terminal method. On the basis of this principle, field experiments and laboratory experiments were carried out with a soil conductivity meter developed based on ARM and a portable oscilloscope conductivity meter. The soil conductivity meter based on ARM is mainly composed of ARM, GPS, signal generating circuit and signal conditioning circuit. The differential circuit is introduced to improve the measurement accuracy by enhancing the feedback signal and suppressing the input of noise signal. Portable oscilloscope conductivity meter is composed of portable oscilloscope, signal generating circuit, signal conditioning circuit and computer display software. The main oscilloscope uses DSCope C20P, a digital oscilloscope based on USB developed by DreamSourceLab, which has excellent performance in waveform processing and data prefetching. The experimental data of the two instruments are compared with the laboratory measurements. The EC values obtained by portable oscilloscope soil conductivity meter were compared with result of laboratory EC values after removing the points seriously affected by noise and experimental errors, and R2was 0.6299. The EC value obtained by ARM soil conductivity meter were compared with result of chemical method, and R2was 0.5057. The experimental results show that the accuracy of the portable oscilloscope conductivity meter is significantly higher than the soil conductivity meter based on ARM.