A magnetometer is a device that measures magnetism. It measures the strength and direction of magnetic fields, including the ones on or near the Earth and the ones in space. The first magnetometer was created by Carl Friedrich Gauss. He devised a simple absolute magnetometer that consisted of a permanent bar magnet suspended horizontally by a gold fibre. The period of oscillation of the suspended magnet in the Earth’s magnetic field gave a measure of field strength.
Types of Magnetometer
Magnetometers are sensitive and they can be used to find archaeological sites, iron deposits, shipwrecks and other things that have a magnetic signature. There are two types of magnetometers and they are:
- Vector Magnetometers
- Scalar Magnetometers
Vector magnetometers measure the vector components of a magnetic field. Scalar magnetometers measure the magnitude of the vector magnetic field.
Magnetometers that are used to study the Earth’s magnetic field express the vector components of the field in terms of declination and the inclination.
Magnetometers may also be classified by their intended use as stationary magnetometers and mobile magnetometers. Stationary magnetometers are installed to a fixed position and measurements are taken while they are stationary. Mobile magnetometers are used while in motion and are manually carried or transported in a moving vehicle.
Specifications of Magnetometers
The performance and capabilities of magnetometers are described through their technical specifications. Following are the major specifications:
- Sample Rate – Sample rate is the amount of reading given per second. Sample rate is important in mobile magnetometers. The sample rate and the vehicle speed determine the distance between measurements.
- Resolution – It is the smallest change in a magnetic field that a magnetometer can resolve.
- Bandwidth or Bandpass – Bandwidth characterizes how well a magnetometer tracks rapid changes in magnetic field.
- Thermal Stability – The dependence of the measurement on the temperature.
- Noise – It is the random fluctuations generated by the magnetometer sensor or electronics.
- Quantization Error – It is the error caused by recording roundoff and truncation of digital expressions of the data.
- Heading Error – Heading error is the change in the measurement due to a change in the orientation of the instrument in a constant magnetic field.
- Gradient Tolerance – The ability of a magnetometer to obtain a reliable measurement in the presence of a magnetic field gradient.
Uses of Magnetometers
Magnetometers have a diverse range of applications from locating sunken ships to monitoring heart beats. Depending on the application, magnetometers can be deployed in spacecraft, aeroplanes, towed at a distance behind quad bikes and lowered into bore holes.
- For defensive purposes, navies use arrays of magnetometers laid across sea floors around ports to monitor submarine activity.
- Many smartphones make use of miniaturized magnetometers that are used to detect magnetic field strength and are used as compasses.
- A fluxgate magnetometers are used in space travel expeditions to measure the magnitude and direction of the magnetic field of a planet or a moon.
- Magnetometers are used in oil exploration to show location of geologic features that make drilling impossible.
- Magnetometers are used to detect archaeological sites, shipwreck and other submerged objects.
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