In this paper we use the eddy current method to detect imperfections on a carbon fiber reinforced plastic plate. The constructed eddy current probes use ferrite cores to increase the excitation field on the plate zone under them. Due to the low conductivity of the material under test, the excitation frequency was in- creased three orders of magnitude in relation to frequencies usually used for aluminum inspection. Different tests were performed by changing the probe design and by changing the excitation method. When two excita- tion coils were used, and one coil as detector, two different configurations were tested.