Development and validation of a low-cost direct current resistivity meter for humanitarian geophysics applications
Dana Sirota, Jeffrey Shragge, Richard Krahenbuhl, Andrei Swidinsky, Nicaise Yalo, John Bradford
Abstract
ABSTRACT Insufficient access to safe drinking water is one of the most challenging global humanitarian issues. The development of low-cost microcontrollers and the widespread availability of cheap electronic components raise the possibility of developing and using low-cost geophysical instrumentation with open-source designs and software solutions to circumvent geophysical instrumentation capital cost issues. To these ends, we alter an existing low-cost direct current (DC) resistivity meter design and develop an optional modular Raspberry Pi data-logging system to improve the unit’s functionality and usability and to ensure data integrity. Numerical modeling and physical testing demonstrate that the system is more robust than previously published low-cost designs and works in a more diverse range of geologic scenarios — especially conductive environments. Our instrument was tested in a Geoscientists Without Borders project jointly run between researchers from Colorado School of Mines (CSM) and Université d’Abomey-Calavi (UAC), Cotonou, Benin. A key project component involved CSM and UAC students constructing and validating two low-cost DC resistivity meters and then using these instruments for fieldwork aimed at better characterizing and monitoring the health of a local aquifer used as a groundwater source for communities in the Cotonou region. The low-cost instruments were successfully used alongside a commercial resistivity meter to acquire data for 2D inversion of aquifer hydrostratigraphy, indicating the presence of a clay-sand contact. The costs of the redesigned instrument and data logger, respectively, are $177 and $108 (in 2021 USD) with future cost reductions possible, which are fractions of the price of commercial resistivity meters.