Apparatus and method(s) in biomagnetic measurements

The present invention relates to apparatus and method(s) for measuring magnetic field(s), and in particular magnetic field signals which vary with time such as magnetic fields in biological systems (biomagnetic fields) and, in particular, the magnitude of magnetic field(s) which vary with time. In particular, the invention provides an apparatus for measuring magnetic fields (such as hearts in magnetocardiography (MCG)) in human and animal subjects (e.g. bovine or equine animals such as cows, or horses, or animals of similar form) comprising: at least one sensor module (50), the sensor module (50) comprising: at least one magnetometer e.g. an atomic magnetometer sensor (10) having a precessing atomic magnetisation vector (M) in a magnetic field; at least one field varying member (28) (e.g. coil(s) associated with the at least one sensor (10) configurable to restrict a magnetic field experienced by the sensor (10) (e.g. a static component of the magnetic field) in one direction or in two directions orthogonal to one another; a structure (52) for receiving a subject and configured to position the sensor module (50) with respect to a subject (e.g. with respect to a heart of a subject).