Development of a Current Injection-Type Impedance Measurement System for Monitoring Soil Water Content and Ion Concentration

This study was conducted with the aim of developing a circuit system that enables the measurement of the moisture content and ion concentration with a simple circuit configuration. Our previous studies have shown that soil can be represented by an equivalent circuit of a parallel circuit of resistors and capacitors. We designed a circuit that can convert the voltage transient characteristics of the soil when a current is applied to it into a square wave and output frequency information and developed an algorithm to analyze the two types of square waves and calculate R and C. Normal operation was confirmed in the range of 10 k omega-1 M omega for the designed circuit, and the calculation algorithm matched within a maximum error of 5%, thus confirming the validity of the program. These successfully confirmed the changes in the water content and ionic concentration. The soil moisture content measurement succeeded in measuring a maximum error of about 10%, except at one point, and the soil ion concentration measurement succeeded in measuring a maximum error of 6.6%. A new, simple, noise-resistant moisture content and ion concentration measurement circuit system with square wave output has been realized.

Automated summary

This study aimed to develop a simple circuit system for measuring moisture content and ion concentration. By designing a specific circuit and algorithm, the voltage transient characteristics of the soil were successfully converted into square waves, from which the resistors and capacitors values were calculated. Experimental results demonstrated the effectiveness of this new circuit system in accurately measuring water content and ion concentration.