A sensor arrangement for determining a process variable of a medium in a containment comprises a sensor apparatus, a magnetic field apparatus, and a detection apparatus. The magnetic field apparat produces a magnetic field that penetrates the sensor apparatus, the detection apparatus and partially the medium. The sensor apparatus is embodied such that a magnetic property of a component of the sensor apparatus depends on the process variable, and the magnetic field of the magnetic field apparatus is influenceable by the sensor apparatus as a function of process variable. The detection apparatus is embodied to register a variable related with the magnetic field, especially the magnetic flux density, the magnetic susceptibility or the magnetic permeability, and, based on that variable, to determine the process variable. The sensor apparatus is arranged within an internal volume of the containment and the detection apparatus is arranged outside of the containment.