Design and Implementation of an Induction Probe for Simultaneous Measurements of Permittivity and Resistivity

Abstract

In this paper, we propose a discussion concerning the design and implementation of an induction probe for electrical SPECTROscopy which performs simultaneous and not invasive measurements on the electrical RESistivity ρ and dielectric PERmittivity εr of the terrestrial ground and concretes (SPECTRORESPER probe). In order to design a SPECTRORESPER which measures ρ and εr with inaccuracies below a prefixed limit (10%) in a band of low frequencies (B=100kHz), the probe should be connected to an appropriate analogical digital converter (ADC), which samples in uniform or in phase and quadrature (IQ) mode, otherwise to a lock-in amplifier. We develop a large number of numerical simulations, applying the Mathcad program, which provide the optimization of the height above ground, the electrode-electrode distance and working frequencies minimizing the inaccuracies of the SPECTRORESPER, in galvanic or capacitive contact with terrestrial soils or concretes, of low or high resistivity. As final findings, we underline that the performances of a lock-in amplifier are even better compared to an IQ ADC with high resolution bit, under the same operating conditions. As consequences in the practical applications: if the probe is connected to a system of data acquisition as an uniform or rather an IQ sampler, then it could be commercialized for companies of building and road paving, being employable for analyzing “in situ” only concretes; otherwise, if the data acquisition system is a lock-in amplifier, the marketing would be for companies of geophysical prospecting, involved to analyze “in situ” even terrestrial soils.