Abstract: The unit is used to produce an electrical displacement-measurement signal in response to the internal movements of a core of magnetic material connected to a probe of a feeler for measuring linear magnitudes. The unit comprises, aligned within a tube (8), two coils (9), a spacer (10) of elastic material compressed between the two coils, and two end flanges (11) of the tube between which the two coils and the elastic spacer are gripped. The insertion of the elastic spacer between the two coils is provided in order to make symmetrical, in relation to the zero position of the system denoted by a median plane (P), the linearity error generated by the differing manufacturing dimensions of the elements aligned within the tube.