The ironless inductive position sensor is a novel linear position-sensing device that should exhibit immunity to external magnetic fields while simultaneously guaranteeing high-precision measurements in harsh environments. This paper focuses on the characterization of the sensor's working principle and magnetic field immunity. The sensor is tested, with both voltage and current supply, with different dc and slowly varying magnetic field patterns in order to prove its immunity and analyze the differences and similarities between the two supply cases. The measurements are performed with a test bench on a custom prototype, which is especially manufactured for this purpose.