# Design, Development and Application of a Modular Electromagnetic Induction (EMI) Sensor for Near-Surface Geophysical Surveys

## TL;DR

This paper introduces a portable, modular EMI sensor for geophysical surveys that allows adjustable settings and provides precise conductivity measurements.

## Contribution

The novel contribution is an open-source, modular EMI sensor with adjustable transmitter-receiver configurations and precise conductivity measurement capabilities.

## Key findings

- The sensor measures apparent conductivity from 1 mS/m to 1000 mS/m with 1.0 mS/m resolution.
- It supports up to four receiving antennas and adjustable acquisition frequencies between 3 and 50 kHz.
- The device is portable, battery-operated for 4 hours, and includes synchronized time and location stamps for data.

## Abstract

Low-frequency electromagnetic induction (EMI) is a non-invasive geophysical method that is based on the induction of electromagnetic (EM) waves into the subsurface to quantify changes in electrical conductivity. In this study, we present an open (design details and software are accessible) and modular system for the collection of EMI data. The instrument proposed allows for the separations between the transmitter to be adjusted and up to four receiving antennas as well as the acquisition frequency (in the range between 3 and 50 kHz) to permit measurements with variable depth of investigation. The sensor provides access to raw data and the software described in this study allows control of the signal processing chain. The design specifications permit apparent conductivity measurements in the range of between 1 mS/m and 1000 mS/m, with a resolution of 1.0 mS/m and with a sampling rate of up to 10 samples per second. The sensor allows for a synchronous acquisition of a time stamp and a location stamp for each data sample. The sensor has a mass of less than 5 kg, is portable and suitable for one-person operation, provides 4 h of operation time on one battery charge, and provides sufficient rigidity for practical field operations.