Development and validation of a low-cost direct current resistivity meter for humanitarian geophysics applications

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 electronics 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 DC resistivity meter design and develop an optional modular Raspberry Pi data-logging system to improve the unit's functionality, usability and to ensure data integrity. Numerical modeling and physical testing demonstrates that the system is more robust than previously published low-cost designs and works in a more diverse range of geological scenarios - especially conductive environments. Our instrument was tested in a Geoscientists Without Borders (GWB) project jointly run between researchers from Colorado School of Mines (CSM) and Universit矤'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 cost 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.

Design and Implementation of a Composite Array Resistivity Data Logger for High-Resolution 2D Inversion Modeling

“…According to a study by R. Kumar et al (2016), high voltage and high current can help to overcome the limitations of low SNR and high RMS misfit in DC resistivity measurements. The authors found that increasing the current and voltage in the measurement system can improve the quality of the acquired data and reduce the uncertainty in the results (Sirota et al, 2022).…”

Fictitious Point Technique Based on Finite-Difference Method for 2.5D Direct-Current Resistivity Forward Problem

“…Direct-current resistivity is a surface geophysical method that can provide essential information for investigating subsurface geological structures by injecting electric current into the Earth and measuring the corresponding voltage. It can find applications in mineral resource exploration [1][2][3], environmental and urban geological surveys [4][5][6][7], and humanitarian geophysics [8]. Regular two-dimensional (2.5D) and three-dimensional (3D) surveys are now conducted.…”

A Legendre Spectral-Element Method to Incorporate Topography for 2.5D Direct-Current-Resistivity Forward Modeling

“…This method entails measuring the electrical resistivity of various materials and structures beneath the surface by transmitting a direct current through the ground and assessing the resulting potential differences. Due to their environmentally friendly nature and cost-effectiveness, direct-current measurements have found extensive application in diverse fields, including engineering studies [1-4], hydro-geological work [5][6][7], mineral resource exploration [8,9], and humanitarian geophysics [10]. In these geophysical explorations, the topography is typically non-flat, and the presence of the terrain will lead to false anomalies in apparent resistivity [11].…”