The 2-wire method, by taking advantage of appropriate external masses as a reference (metal surfaces, tubes, neutral conductor, etc.), is particularly useful in private environments where, because of logistic problems, it is not possible to use the 3-wire method. The device allows carrying out measurements with a wide measuring range (up to 50kOhm) with an efficient internal compensation of the disturbance effects found on the installations. GEO416 is provided with an internal memory for saving measurements and with an optical/USB interface for transferring measured data onto the PC