  A new apparatus has been developed to measure the conductivity of rock
samples. The probe, which consists of multi-coil transmitters and receivers
doesn't require physical contact with the samples. The measurement is based on
the induction principle. The measurement system is validated by using saline
solutions and water-saturated sands of known conductivity. This work presents
details of the development of a system of magnetic resistivity measurements by
magnetic induction for petrophysical applications. The first application
consists of measuring the resistivity of the core plug which is 0.038 m in
diameter. Currently the system is operating properly at a frequency of 50 kHz
with a current of up to 500 mA at 20 {\deg}C. During the study two types of
samples were investigated: aqueous solutions with conductivities between 1 to
100 mS/cm and rocks. Several tests were carried out with the objective of
investigating the performance of the instrument, such as the experiment to
obtain sensitivity for the measurement system as a function of the current
applied to the transmitter coil.
