Barnard Microsystems Limited

Developing Unmanned Aircraft Systems to benefit Mankind

Precision magnetometer - Magnetometer

Magnetometer

Diagram of the Earth’s magnetic field from www.philips.com .

Applications of high sensitivity magnetometers:

A magnetometer is used to measure the strength of the Earth’s magnetic field. To get a feel for the sensitivity of these magnetometers, the earth’s magnetic field strength in London on 24 SEP 2005 was 48,489 nT, increasing by 31.43 nT per annum. The 0.1 nT accuracy of the potassium magnetometer is very close to the 0.086 nT daily increase in the earth’s magnetic field strength, in London.

  • geophysical surveys measuring the minute variations in the Earth’s magnetic field strength, to identify the location of mineral Kimberlite pipes and provide hints as to the location of hydrocarbon deposits
  • compliment seismic surveys, in oil and gas exploration work
  • detect underground metallic structures, such as pipes, tunnels, barrels, items of archaeological importance
  • detect the presence of metallic structures in dense foliage, such as trucks, pipes, crashed aircraft, artefacts from lost civilisations, using differential magnetometry
  • detect metallic structures under rivers and oceans, such as pipes, ship wrecks
  • detect the presence of intruders in dense undergrowth, such as armed militia, with metal guns, possibly travelling on metal bicycles, motorbikes, or, in metal trucks…

Magnetometer

The Earth's total magnetic field intensity in nT.

from http://www.gemsys.ca/PDFDocs/MM3_GEM_Brief_Review_of_Quantum_Magnetometers.pdf

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Sensor noise as a function of frequency

from JamesMacnae presentation at SEG 2006

Magnetometer

Magnetometer

Typical Detection Range For Common Objects

Ship 1000 tons

0.5 to 1 nT

at 244 m

Light Aircraft

0.5 to 2 nT

at 12 m

Pipeline (12 inch)

1 to 2 nT

at 60 m

Pipeline (6 inch)

1 to 2 nT

at 30 m

Automobile

1 to 2 nT

at 30 m

100 Kg of iron

1 to 2 nT

at 15 m

45 Kg of iron

0.5 to 1 nT

at 9 m

4.5 Kg of iron

0.5 to 1 nT

at 6 m

0.45 Kg of iron

0.5 to 1 nT

at 3 m

Screwdriver 125 mm

0.5 to 2 nT

at 4 m

- from http://www.heritagegeophysics.com/Magnetometers/Magnetometers.htm

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Characteristics of some magnetic field sensors

sensor

accuracy

in pT

noise level

in fT/sqrt(Hz)

solid state magnetoresistance

eg. Honeywell HMC1001 / HMC1002

350,000

180,000

Fluxgate 3 axis magnetometer

eg. Bartington Mag-03

250,000

~6,000

low noise ver

Cesium beam magnetometer

eg. Scintrex CS-3L

2,500

600

Potassium beam magnetometer

eg. Gem Systems GSMP-30A

100

700

high sens option

low temperature (liquid Helium) SQUID

eg. Supracon

only noise limited

3.5

For reference, the Earth’s magnetic field strength at London on the 24 th September 2005 was 48,489,000 pT.

Magnetic field strength is often quoted in Gauss. 1 Tesla = 10,000 Gauss.

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The Honeywell magnetoresistance sensor

Magnetometer

Magnetometer

- from Honeywell application Note An211.pdf as found on www.magneticsensors.com site.

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The Bartington Mag-01 and Mag-03 Fluxgate Magnetometer

. Magnetometer

Above: the Mag-01 instrument.

Magnetometer

- from http://www.bartington.com/

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Above and below: the Mag-01MS from http://www.bartington.com/

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Magnetometer

Above and below: the Mag-03MC from http://www.bartington.com/

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Example of a Potassium Magnetometer: GEM Systems GSMP-30

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Small experimental Cesium magnetometer from NIST

Magnetometer

- from Electronics Weekly, 9th January 2005

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The SQUID = Super Conducting Quantum Interference Device magnetic field sensor

from “LTS SQUIDS: …” by A. Chwala et al, www.supracon.com

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Magnetometer

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Comparative sensor noise during winter atmospheric (“sferic”) disturbance

Magnetometer

From James Macnae presentation at SEG 2006

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