Magnetometer Design


Types of Magnetometers

General site about magnetomters:

Alternating Gradient Magnetometer

Anisotropic Magnetoresistance (AMR)

Made of Permalloy, a thin nickel-ironfilm deposited on silicon. The film changes resistance (2-3%) in the presence of a magnetic field.

Giant Magnetoresistance (GMR)

Hall Effect Sensor

Moving Coils

Proton Precession Magnetometer (PPM)

When molecules are aligned by a field and the field is then removed, the molecules precess at a frequency proportional to the ambient field strength.
Solenoidal or toroidal configuration.

Superconducting Quantum Interference Devices (SQUID)

Vector/Scalar Helium Magnetometer (VSHM) & Optically Pumped Magnetometer


Final Considerations

Fluxgate Magnetometer

PDF of Professor Gill Pratt's Masters Thesis: A Blind Man's Compass


Magnetoinductive magnetometers are relatively new, with the first patent issued in 1989. This sensor is simply a single winding coil on a ferromagnetic core that changes permeability within the Earth's field. The coil is the inductance element in a L/R relaxation oscillator. The oscillator's frequency is proportional to the field being measured. A static DC current is used to bias the coil in a linear region of operation (see Figure 3). As the sensor is rotated 90º from the applied magnetic field, the observed frequency shift can be as much as 100%. The oscillator frequency can be monitored by a microprocessor's capture/compare port to determine field values. These magnetometers are simple in design, inexpensive, and have low power requirements. Their temperature range is -20ºC to 70ºC, and they are repeatable to within 4 mG. Automatic assembly and axis alignment are difficult due to the sensor's small size and its physical configuration.


Mu Metal


© Olin College NASA Study 2004