Magnetometry measures magnetic fields or magnetic responses using a specified sensor and calibration. Different instruments respond to a field component, magnitude, gradient or magnetic moment.
A Hall sensor converts a transverse charge-deflection voltage into a field estimate; a fluxgate uses a driven magnetic core; an atomic magnetometer measures field-dependent spin dynamics. Sensitivity must be stated together with bandwidth and measurement geometry. A very small noise density does not alone establish absolute accuracy, because offsets, calibration and environmental fields can remain.
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