The electrical RESistivity and dielectric PERmittivity measuring device (RESPER meter) for non-invasive investigation of enviroment is a survey device exploiting the electrical induction by means of a capacitive coupling with media as terrestrial soils and concretes.
Abstract RESPER meter utilizes a four-electrode probe to inject a radio frequency voltage into a medium and to register an induced current signal. Complex transfer impedance can be determined from a ratio between a potential measured across two electrodes, and an induced current flowing in the medium. Electrical parameters of resistivity and permittivity characterizing the medium can be established from the transfer impedance, using inversion formulas that also take into account the geometric ratio between the distances and position of the electrodes.
In-depth analysis RESPER exploits the in-phase and quadrature under sampling technique which, together with some numerical operations performed by a microcontroller, allows the device to attain a required performance. Indeed, it is possible to execute just a number of numerical integrations which, combined with some circuit solutions, can reduce the amplitude and phase errors of the acquired signal. The device can operate at variable frequency, even maintaining a suitable under-sampling frequency to fully exploit the analogical-digital acquisition performance both in velocity and dynamic range.