2023 ASEE Annual Conference & Exposition

Electrical Resistivity (ER) surveys have been used to investigate soils for over a century but a “black box” traditionally surrounds commercial ER equipment. This work proposes the design of an intuitive, low-cost ER meter for hands-on geotechnical education. The prototype leverages $40 worth of integrated-circuit modules and less than 80 lines of open-source commands to inject a current into the ground and measure the site’s potential response. The device was validated against test circuits with ohmic values ranging over 4 orders of magnitude and yielded marginal mean absolute percentage error less than 3%. The proposed ER meter was thereafter implemented in a tabletop laboratory setting to perform Constant Separation Traversing (CST) surveys using Wenner array along parallel profiles. The resulting CST matrix showed values of apparent resistivity consistently in agreement with the modeled earth stratum. Over the extent of a buried Styrofoam feature, the device generated measurements up to 70% higher and identified clear lateral disruptions in subsurface conditions. Overall, the proposed ER meter proved to be a tool well suited for tabletop experiments and capable of characterizing complex test beds. Its open-science design addresses the issues of the “black box” surrounding proprietary equipment and makes it accessible to the community at large for a fraction of the cost of commercial units. With practical applications for hands-on teaching and interactive learning, this work makes geotechnical laboratory education more engaging and relevant. As such, it has the potential to modernize STEM curricula and advance the fundamental understanding at the intersection of technology and environment.