Zero field is sometimes required, but at other times only the precise knowledge of the field at the site of the experiment is sufficient. It can allow you to discriminate between magnetically induced events, and events of interest. Additionally, methods have been developed that make it possible to predict the field at a location based on surrounding measurements. This usually requires several sensors distributed around the experimental volume. For room temperature setup, sensors such as the Mag-13, Mag612, Mag619 and Mag690 are well-suited, with each offering particular benefits. The Mag612 and Mag619 are ideal where space is constrained. For cryogenic applications, the Mag-01H and Mag F probes provide high accuracy measurements at very low temperatures. When passive shielding is also used, these sensors can be used to map the remanent magnetisation within the shield, before and after experiments, thereby increasing knowledge of the surrounding field.