The present invention relates to a sensor assembly arranged to be disposed in a body for measuring a physiological variable. A basic idea of the present invention is to provide a sensor and guide wire assembly which communicates with an external unit by an inductive coupling between a first coil provided in the sensor assembly and a second, external coil which is disposed in or connected to the external unit. The external unit is preferably the same unit that is used to numerically or graphically display the physiological variables that are measured with the sensor and guide wire assembly. With the terminology introduced above, it should here be clear that both the signal transfer from the sensor as well as the energy feeding from the external unit to the sensor may be accomplished through the inductive coupling between the first and second coils.