An ironless position sensor is a novel sensing structure which exhibits intrinsic immunity to external magnetic fields, since it is characterized by air-cored supply and sensing windings. This new solution may be of significant interest for applications where external magnetic fields are present. In this paper, an analytical model of the working principle of the sensor is proposed. The effect of the moving coil flux on the overall sensed magnetic flux is described. The modeling of such a sensor acts as a design tool of primary importance in the framework of the synthesis of the device. The model is verified by simulations of a finite element structure of the sensor, expressly prepared for this purpose.