The paper deals with a new set of magnetic probes which has recently installed in JET in order to improve the field measurements in the proximity of the iron. The set consists of six Limb probes, attached to the upper horizontal iron yokes, and one Collar Probe, inserted in the collar region of the iron structure. The probes include pick-up coils, flux loops, Hall sensors, and a temperature sensor. The data provided by the system are regularly acquired and recorded within the set of JET Pulse Files. They are ready for use in studies implyingmeasurement of the stray field due to the residualmagnetization, as well as for all the modeling activities involving 3D studies, in particular resistive wall mode studies, more accurate modeling for the vertical stabilization, interactions between NBI and magnetic field. In addition, the experience gained with Hall transducers is considered valuable in view of their potential use in ITER. Unlike the limb probes, the collar probe did not pass the functional commissioning, due to an unexpected discrepancy between the signals from Hall sensors and pick-up coils. The analysis illustrated in the paper shows how a critical assessment of the local configuration and a suitable magnetic modeling could solve this commissioning issue. In the case of the collar probe, it is demonstrated that the measurements are acceptable, since the observed discrepancy is due to a local geometrical effect, which was not known at the time of the installation. The paper also includes some other more general information, which might be useful for JET studies.