Portable Impedance Meter for Focused Impedance Applications

Focused Impedance Method is a technique that employes a measurement configuration with 4 to 8 electrodes to localize a small volume in a conductor by its 3D sensitivity. Thanks to this characteristic it could be therefore especially useful in biomedical applications, where an organ within a close proximity to the body surface is of interest. The availability of a medical investigation tool that is portable and easy to use would allow medical operators to carry out checks and monitoring of patients even at home, avoiding moving to patients who are particularly limited in their movements or in critical health conditions. In this paper a portable system for Focused Impedance applications is presented, that relies on a personal computer and a commercial audio board for signal generation, acquisition and elaboration. Because of this approach, the rest of the system, consisting in an analog front end and a microcontroller-based switching matrix for changing electrode configuration during measurement, is greatly simplified and can be easily reproduced by any researcher willing to experiment with the Focused Impedance technique. To this purpose, both the system software, including a simple calibration procedure for obtaining high accuracy while maintaining low complexity, and the firmware running on a Raspberry Pi Pico microcontroller required for switching operations, are freely available for encouraging experimentation with the system we propose.