Abstract
A portable soil electrical conductivity (EC) detector was developed and its performance was tested. The ECdetector adopts a four-electrode method and consists of three parts: a probe with four electrodes, a control and display unit,and the data processing software. The probe injects a constant electrical current into soil and detects the voltage drop betweentwo output electrodes. The voltage drop is then used to estimate the soil EC. The control and display unit consists of severalsections including the microprocessor, power, the constant current source sections, the A/D conversion section, the displaysection, and the communication section. All sections were designed in a circuit board to measure, display, and record signalsfrom the probe. The performance test showed that the measured voltage drop had high correlation with soil ECs obtained fromsoil extract solution. The highest correlation coefficient was obtained when the distance between an inputting electrode anda detecting in the same side was 15 cm and the distance between two detecting electrodes was 30 cm. Three nonlinearregressions were attempted to describe the correlation: the power function regression, the polynomial regression, and theexponential function regression. The best estimation was observed with the power function model (R2 = 0.994) with two modelparameters: intercept and power. These model parameters had little variation and hence the model was reliable. All resultsshowed that the developed detector was practical.
Published Version
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