Essay On Magnetometer

THE PROTON PRECESSION MAGNETOMETER

The proton precession magnetometer is most commonly used for land-based magnetic surveys.This magnetometer only measures the total amplitude (size) of the earth magnetic field. Usually these type of measurements are referred to as total field measurements.
The proton precession magnetometer is so named because it utilizes the precession of spinning protons or nuclei of the hydrogen atom in a sample of hydrocarbon fluid to measure the total magnetic intensity. The sensor component is a cylindrical container filled with a liquid rich in hydrogen atoms surrounded by a coil.kerosene, alcohol and water are the commonly liquids used. On closing the switch a DC current from the battery is directed through the coil, producing a relatively strong magnetic field in the fluid filled cylinder. The hydrogen nuclei (protons) behave like minute spinning dipole magnets ,become aligned along the direction of the applied field(i.e along the axis of the cylinder).
Upon opening the switch the power is cut to the coil, given that the earth magnetic field generates a torque on the aligned, spinning hydrogen nuclei, they begin to precess around the direction of the earth total field.As the protons precess,the precession produces a time varying magnetic field which induces a small alternating current in the coil such that the frequency of precession of the nuclei is equal to the frequency of the AC current.The proton precession measures the frequency of the oscillatin field and since its equal to the precession frequency of the protons it can be used to determine the strength of the external field.
The proportionality constant which relates frequency to field intensity is a well-known atomic constant the gy...

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...xhibit the usually pattern common to a small magnet as shown below in fig 1.

The direction of the field lines at the equator is horizontal while at the north and south magnetic poles its vertical.This geometry is important in interpretation of magnetic anomalies.The earth total field intensity is not perfectly asymmetric about the geographical northpole eg the north magnetic pole in northern Canada is more than 1000miles from the geographical pole.
The earth cannot be exactly represented by a single bar magnet but has numerous higher order poles and very large –scale anomalous features owing to unknown characteristics of the generating mechanism in the earths core. As shown in fig 1 the solar wind or constant flux of particles and electric currents from the sun distort the field lines.The deviation from asymmetric field is the anomalous set of features in the