Development and test of a low cost portable soil apparent electrical conductivity sensor using a Beaglebone Black

Abstract. The adoption of soil apparent electrical conductivity (ECa) sensors has increased in precision agricultural systems. The ECa sensors have low cost and generally the ECa values correlate well with soil chemical and physical attributes. The objective of this work was to develop a portable soil sensor for measuring soil apparent electrical conductivity that could be used in mountainous areas and in small farms. The developed system was based on the electrical resistivity method and uses an alternating current signal. The system measured the electrical conductivity by applying a square wave signal at a frequency defined by the user. The acquired data was georeferenced using a low cost GPS receiver. The sensor system was developed using a Beaglebone Black that is a low cost single board computer. A user interface was developed in C++ and a touch screen with a resolution of 800x480 pixels was used to display the results. This interface performed statistical analysis and the results were used to guide the user to identify more field locations to be sampled to increase mapping accurace. The system was tested in a coffee plantation located in a mountainous area in Minas Gerais, Brazil. The system worked well in mapping the apparent soil electrical conductivity.