Giant Magnetoimpedance (GMI) magnetometers are one of the most recent families of magnetic transducers, being characterized by their potential to achieve high sensitivities. The sensitivity of magnetic transducers is directly related to the sensitivity of its sensor elements. Thus, optimizing the sensitivity of these sensor elements is a critical part of the magnetometers development chain. This paper describes an automatic characterization system designed for the measurement of the electrical impedance of Giant Magneto- Impedance samples. The measurement uncertainties of the system were verified and discussed. The high speed of measurement attained with the use of this system, implemented in LabVIEW, allows for the rapid determination of the optimal operational point of GMI magnetometers.