Introduction: A Proton Precession Magnetometer is an instrument that measures the scalar intensity of the local magnetic field and relies upon the proton-precision measurement technique. This is a well-established technique and is successfully implemented in classical proton precision magnetometers.
PPM derives its name from the fact that it utilizes the Precession of spinning protons or nuclei of the hydrogen atoms in a sample of hydrocarbon fluid, to measure the total magnetic field intensity. With this primary purpose of generating the ground based magnetic data, the Indian Institute of Geomagnetism IIG for the last 3 decades have been developing low cost high precision 0.
PPM utilizes the Precession of spinning protons or nuclei of the hydrogen atoms in a sample of Hexane to measure the total magnetic intensity. The spinning protons in this sample are temporarily aligned or polarized by application of a uniform magnetic field hundreds of Gauss generated by passing a current of A through a coil of inductance 30 mH [2].
So the electrical resistance is the greatest when the current is parallel to an external magnetic field so that the field can be measured correctly. The calibration of magnetometers is usually carried out using coils supplied by an electrical current to create a magnetic field.
This helps characterize the sensitivity of the magnetometer. In fact, the uniformity of the calibration coil is a key element across several applications; this explains why coils like Helmholtz coils are commonly used in a single axis or a three-axis configuration.
Also, in demanding applications a high homogeneity magnetic field is necessary. So magnetic field calibration can also be done using a Maxwell coil, cosine coils, or calibration in the highly homogenous magnetic field of the earth. Magnetometers are mainly classified under two categories: scalar and vector manometers. These scalar magnetometers can be further differentiated as proton precession, overhauled effect and ionized gas magnetometers.
A vector manometer, on the other hand, is used to measure the magnitude and direction of the magnetic field. This magnetometer measures the resonance frequency of the protons in a magnetic field by using nuclear magnetic resonance NMR. When a polarizing DC current is sent through a solenoid, it creates high magnetic flux around the hydrogen-rich fuel like kerosene and some of the protons get aligned with this flux. Upon the release of the polarizing flux, the frequency of precession of the protons to normal realignment is used to measure the magnetic field.
Here a low power radio frequency signal is used instead of the solenoid for aligning the protons. So when an electron-rich liquid combines with hydrogen, it is subjected to a radio frequency RF signal. With overhauled effect the protons get coupled to nuclei of the liquid.
Given how the precession frequency is linear with the magnetic flux density, it can be used to measure the strength of the magnetic field. Moreover, boasting faster sampling rates, these magnetometers need far less power. More accurate than the proton precession magnetometers, ionized gas magnetometers consist of vapor chambers filled with the vapors like cesium, helium, and rubidium; and photon emitter light. When the cesium atom meets the photon of the lamp, energy levels of the electrons fluctuate at a frequency corresponding to the external magnetic field, thus helping measure the intensity of the magnetic field.
Used for high sensitivity applications, here the fluxgate sensor drive -made up of a magnetically susceptible core wound by two coils of wire - has an alternating drive current running a permeable core material. One coil here has AC current running through it and the constantly changing field induces an electrical current in the second coil. This current change is based on the background field. So the alternating magnetic field, and the induced output current, are not in sync with the input current and the extent varies as per the strength of the background magnetic field.
These are made up of semiconductor devices where the electrical resistance changes as per the applied or ambient magnetic field. These comprise two superconductors separated by thin insulating layers to form two parallel junctions. Given how sensitive they are to the low range intensity fields, they are most often used to measure the magnetic fields produced by the brain or heart in medical applications. The core gets magnetized by the magnetic field lines produced inside the coils and the fluctuations in the magnetic field bring about the flow of electrical currents.
It is the changes in voltage due to this current that are then measured and recorded by the magnetometer. As the coil rotates, the magnetic field induces the sine wave signal in the coil. Given that this signal amplitude is proportional to the strength of the magnetic field, the magnetometer is thus able to measure the latter.
However, this method is outdated today. Magnetometers have several uses today. Let us look at their applications. Compasses : Today, magnetometers have been miniaturized to the point where they are easily included in integrated circuits at a low cost and they are thus increasingly being used as miniaturized compasses MEMS magnetic field sensor. They are used to find and identify magnetic anomalies of various types, and to ascertain the dipole moment of magnetic materials. Surveyors use them in geophysics applications.
Military purposes : Magnetometers are used in defense and navy to carry out submarine activities and submarine detection as well. In fact, countries such as the United States, Canada and Australia have categorized sensitive magnetometers under military technology and they thus control their distribution.
Defense and aerospace: Magnetometers are also used on land, in the air, at and under sea and in space. Oil and gas exploration: Magnetometers are used for drilling discovered wells.
They are used in drilling sensors which are used to detect the direction or path for the drilling processes. Plasma flows : Magnetometers also come in handy for studying the solar wind and planetary bodies. Archaeology : Magnetometers are used to study archaeological sites and detect buried objects.
Metal detection and coal exploration : Since they can detect magnetic ferrous metals, magnetometers make for good metal detectors. Moreover, they can detect them at greater depths when compared to conventional metal detectors.
0コメント