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# Persentation on magnetometer

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definition, working principle, types, and use of magnetometer.

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### Persentation on magnetometer

1. 1. MAGNETOMETER PRESENTED BY Ijaz Ul Haq M Bilal younis Moazam Ali 1
2. 2. MAGNETOMETER  Definition Magnetometer are measurement instruments used for two general purposes: to measure the magnetization of a magnetic material like a ferromagnet, or to measure the strength and, in some cases, the direction of the magnetic field at a point in space. 2
3. 3. OUTLINE  Magnetometer data: what are we measuring?  Ground magnetic signatures of  Earth’s magnetic field  Ring currents  Auroral currents 3
4. 4. MAGNETIC FIELD MEASUREMENT  magnetic field sensors can be divided into two components I. vector component II. Scalar magnitude types. 4
5. 5. MAGNETIC FIELD FUNDAMENTALS  The vector types can be further divided into sensors that are used to measure low fields (<1 mT) and high fields (>1 mT). 5
6. 6.  Instruments that measure low fields are commonly called magnetometers  High-field instruments are usually called gaussmeters.  Magnetic field sensors are divided into two categories based on their field strengths and measurement  Range: magnetometers measure low fields and gaussmeters measure high fields. 6
7. 7. MAGNETIC FIELD SENSOR 7
8. 8. MAGNETIC FIELD FUNDAMENTALS  An understanding of the nature of magnetic fields is necessary in order to understand the techniques used for measuring magnetic field strength. The most familiar source of a magnetic field is the bar magnet. 8
9. 9. Magnets produce magnetic fields. A magnetic field is a vector quantity with both magnitude and direction properties. 9
10. 10.  The field it produces is shown in Figure. Magnetic field is a vector quantity; that is, it has both a magnitude and a direction. The field of a bar magnet or any other magnetized object, when measured at a distance much greater than its longest dimension, is described by Equation H = 3 ( m × ar ) ar – m / r³ 10
11. 11. Magnetic fields are also produced by electric currents 11
12. 12. MAGNETOMETER  Definition Magnetometer are measurement instruments used for two general purposes: to measure the magnetization of a magnetic material like a ferromagnet, or to measure the strength and, in some cases, the direction of the magnetic field at a point in space. 12
13. 13. OBJECTIVES  Magnetometers are widely used for measuring the Earth's magnetic field and in geophysical surveys to detect magnetic anomalies of various types  They are also used militarily to detect submarines 13
14. 14. TYPES OF MAGNETOMETER  There are two basic types of magnetometer measurement 1. Vector magnetometers 2. scalar magnetometers 14
15. 15. 1. VECTOR MAGNETOMETERS  Vector magnetometers measure the vector components of a magnetic field  measure the component of the magnetic field in a particular direction, relative to the spatial orientation of the device. 15
16. 16. VECTOR MAGNETOMETERS  Low-Field Vector Magnetometers  The Induction Coil Magnetometer  The Fluxgate Magnetomete  The SQUID Magnetometer 16
17. 17. THE INDUCTION COIL MAGNETOMETER  The induction or search coil, which is one of the simplest magnetic field sensing devices, is based on Faraday’s law. 17
18. 18.  This law states that if a loop of wire is subjected to a changing magnetic flux, f, through the area enclosed by the loop, then a voltage will be induced in the loop that is proportional to the rate of change of the flux: e (t )= - dɸ / dt 18
19. 19. Induction or search coil sensors consist of a loop of wire (or a solenoid), which may or may not surround a ferromagnetic core. (a) Air core loop antenna; (b) solenoid induction coil antenna with ferromagnetic core 19
20. 20. THE FLUXGATE MAGNETOMETER  The fluxgate magnetometer has been and is the workhorse of magnetic field strength instruments both on Earth and in space. It is rugged, reliable, physically small, and requires very little power to operate. 20
21. 21. (a) and ring core (b) fluxgate sensors, the excitation field is at right angles to the signal winding axis. This configuration minimizes coupling between the excitation field and the signal winding 21
22. 22. THE FLUXGATE  The heart of the magnetometer is the fluxgate. It is the transducer that converts a magnetic field into an electric voltage 22
23. 23. 2. SCALAR MAGNETOMETERS  Total field magnetometers or scalar magnetometers measure the magnitude of the vector magnetic field  measures the total strength of the magnetic field they are subject to 23
24. 24. SCALAR MAGNETOMETERS The two most widely used scalar magnetometers are the 1. proton precession 2. optically pumped magnetometer 24
25. 25. PROTON PRECESSION  They have a limited magnetic field magnitude measurement range: typically 20 mT to 100 mT. And they have limitations with respect to the orientation of the magnetic field vector relative to the sensor element 25
26. 26. OUTLINE  Magnetometer data: what are we measuring?  Ground magnetic signatures of  Earth’s magnetic field  Ring currents  Auroral currents 26
27. 27. EARTH’S MAGNETIC FIELDS  The Earth's magnetic field is both expansive and complicated. It is generated by electric currents that are deep within the Earth and high above the surface. All of these currents contribute to the total geomagnetic field 27
28. 28. CONTINUE  In some ways, one can consider the Earth's magnetic field, measured at a particular instance and at a particular location, to be the superposition of symptoms of a myriad of physical processes occurring everywhere else in the world.  Magnetic fields are vectors: they have a strength (magnitude) and a direction just like velocity 28
29. 29. MAGNETIC FIELD STRENGTH  The strength of a magnetic field is the magnetic flux density, B.  The units of magnetic flux density is the Tesla or the Gauss 29
30. 30.  1 Tesla (T) = 104 Gauss (G)  The most powerful magnets in the world are superconducting electromagnets. These magnets have magnetic fields of around 20 T. 30
31. 31. CONTIUE • Earth’s magnetic field is  0.000 052T = 52,000 nanotesla (nT) = 0.5 gauss (G) • 1 nanotesla = 10-9 T • Changes in Earth’s magnetic field are typically 5-100 nT 31
32. 32. TESLA  The applied magnetic field will be one tesla when one coulumb charge enters in it perpendicularly with velocity 1 m/s and experience 1N magnetic force.  Also Wb/m2 is the unit of magnetic field. 32
33. 33. HOW MAGNETOMETERS WORK  Magnetometer measures the magnetic field it is applied to. The magnetometer outputs three magnitudes: X, Y and Z. From these three values you can construct the magnetic field vector (magnitude and direction) B= [X, Y, Z] 33
34. 34. COORDINATE SYSTEMS  Because magnetic fields have a direction, in order to communicate about magnetic fields, we need to define a coordinate system.  Three main coordinate systems are used for magnetometer data: – Geographic (XYZ) – Geomagnetic (XYZ or HDZ - BEWARE!!) – Compass-type (HDZ) 34
35. 35. SOME IMAGES OF EARTH MAGNETIC FIELD 35
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