3-Axis Fluxgate

Advantages

+ High sensitivity

+ Measurements along one or multiple axes

+ Robust

+ Low power consumption

Constraints

– Unlimited range down to weak field strengths

– Relatively limited bandwidth

– Large sensor size

– Disturbs the measured field

Metrolab utilizes fluxgate sensors produced by a respected specialist to complement its Hall effect instruments, extending the range to very weak fields.

High Sensitivity for Weak Magnetic Fields

A fluxgate magnetometer consists of a soft iron core with two coils wound around it: a drive coil and a detection coil.

An alternating voltage continuously drives the core through a complete hysteresis cycle, from saturation in one direction to saturation in the other.

The detection coil measures variations in flux within the core.

An alternately saturated magnetic core produces a signal proportional to the surrounding magnetic field

The magnetic permeability of the core – the slope of the B vs H curve – is modulated as the core enters and exits saturation: when unsaturated, the core has the high permeability of soft iron, when saturated, it suddenly drops to the low permeability of vacuum.

This means that the flux density B within the core due to an external field H is also modulated; one can think of the flux due to the external field being cut off when the core saturates, and restored when the core desaturates – hence the name “fluxgate.”

Clever demodulation schemes enable the measurement of the amplitude of this field modulated by the detection coil.

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