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Search-coil Magnetometer
The search coil magnetometer or induction magnetometer, based on an inductive sensor (also known as inductive loop and inductive coil), is a magnetometer which measures the varying magnetic flux. An inductive sensor connected to a conditioning electronic circuit constitutes a search coil magnetometer. It is a vector magnetometer which can measure one or more components of the magnetic field. A classical configuration uses three orthogonal inductive sensors. The search-coil magnetometer can measure magnetic field from mHz up to hundreds of MHz. Principle The inductive sensor is based on Faraday's law of induction. The temporal variation of the Magnetic Flux \Phi through a ''N'' turns circuit will induce a voltage ''e'' which follows : e = - N\frac which can be expressed in a simpler way : e = - N\times S\frac by assuming that the induced magnetic field B is homogeneous over a section ''S'' (the Magnetic flux will be expressed \Phi = B\times S ). The induced voltage (''e'' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Inductive Sensor
An inductive sensor is a device that uses the principle of electromagnetic induction to detect or measure objects. An inductor develops a magnetic field when a current flows through it; alternatively, a current will flow through a circuit containing an inductor when the magnetic field through it changes. This effect can be used to detect metallic objects that interact with a magnetic field. Non-metallic substances such as liquids or some kinds of dirt do not interact with the magnetic field, so an inductive sensor can operate in wet or dirty conditions.Winncy Y. Du, ''Resistive, Capacitive, Inductive, and Magnetic Sensor Technologies'', CRC Press, 2014 , Chapter 4 ''Inductive Sensors'' Principle The inductive sensor is based on Faraday's law of induction. The temporal variations of the Magnetic Flux \Phi through a ''N'' turns circuit will induce a voltage ''e'' which follows: : e = - N\frac which can be expressed in a simpler way: : e = - N\times S\frac by assuming that the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnetization
In classical electromagnetism, magnetization is the vector field that expresses the density of permanent or induced magnetic dipole moments in a magnetic material. Movement within this field is described by direction and is either Axial or Diametric. The origin of the magnetic moments responsible for magnetization can be either microscopic electric currents resulting from the motion of electrons in atoms, or the spin of the electrons or the nuclei. Net magnetization results from the response of a material to an external magnetic field. Paramagnetic materials have a weak induced magnetization in a magnetic field, which disappears when the magnetic field is removed. Ferromagnetic and ferrimagnetic materials have strong magnetization in a magnetic field, and can be ''magnetized'' to have magnetization in the absence of an external field, becoming a permanent magnet. Magnetization is not necessarily uniform within a material, but may vary between different points. Magnetizatio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Waves (Juno)
Waves is an experiment on the ''Juno'' spacecraft to study radio and plasma waves. It is part of collection of various types of instruments and experiments on the spacecraft; Waves is oriented towards understanding fields and particles in Jupiter's magnetosphere. Waves is on board the unmanned ''Juno'' spacecraft, which was launched in 2011 and arrived at Jupiter in the summer of 2016. The major focus of study for Waves is Jupiter's magnetosphere, which if could be seen from Earth would be about twice the size of a full moon. It has a tear drop shape, and that tail extends away from the Sun by at least 5 AU (Earth-Sun distances). The Waves instrument is designed to help understand the interaction between Jupiter's atmosphere, its magnetic field, its magnetosphere, and to understand Jupiter's auroras. It is designed to detect radio frequencies from 50 Hz up to 40,000,000 Hz (40 MHz), and magnetic fields from 50 Hz to 20,000 Hz (20 kHz). It has tw ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Space Research
Space research is scientific study carried out in outer space, and by studying outer space. From the use of space technology to the observable universe, space research is a wide research field. Earth science, materials science, biology, medicine, and physics all apply to the space research environment. The term includes scientific payloads at any altitude from Outer space, deep space to low Earth orbit, extended to include sounding rocket research in the upper atmosphere, and high-altitude balloons. Space exploration is also a form of space research. History Rockets China, Chinese rockets were used in ceremony and as weaponry since the 13th century, but no rocket would escape velocity, overcome Earth's gravity until the latter half of the 20th century. Space-capable rocketry appeared simultaneously in the work of three scientists, in three separate countries. In Russia, Konstantin Tsiolkovsky, in the United States, Robert H. Goddard, and in Germany, Hermann Oberth. The Uni ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnetotellurics
Magnetotellurics (MT) is an electromagnetic geophysical method for inferring the earth's subsurface electrical conductivity from measurements of natural geomagnetic and geoelectric field variation at the Earth's surface. Investigation depth ranges from 300 m below ground by recording higher frequencies down to 10,000 m or deeper with long-period soundings. Proposed in Japan in the 1940s, and France and the USSR during the early 1950s, MT is now an international academic discipline and is used in exploration surveys around the world. Commercial uses include hydrocarbon (oil and gas) exploration, geothermal exploration, carbon sequestration, mining exploration, as well as hydrocarbon and groundwater monitoring. Research applications include experimentation to further develop the MT technique, long-period deep crustal exploration, deep mantle probing, sub-glacial water flow mapping, and earthquake precursor research. History The magnetotelluric technique was introduc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Non Destructive Testing
Nondestructive testing (NDT) is any of a wide group of analysis techniques used in science and technology industry to evaluate the properties of a material, component or system without causing damage. The terms nondestructive examination (NDE), nondestructive inspection (NDI), and nondestructive evaluation (NDE) are also commonly used to describe this technology. Because NDT does not permanently alter the article being inspected, it is a highly valuable technique that can save both money and time in product evaluation, troubleshooting, and research. The six most frequently used NDT methods are eddy-current, magnetic-particle, liquid penetrant, radiographic, ultrasonic, and visual testing. NDT is commonly used in forensic engineering, mechanical engineering, petroleum engineering, electrical engineering, civil engineering, systems engineering, aeronautical engineering, medicine, and art. Innovations in the field of nondestructive testing have had a profound impact on medical im ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eye Movement (sensory)
Eye movement includes the voluntary or involuntary movement of the eyes. Eye movements are used by a number of organisms (e.g. primates, rodents, flies, birds, fish, cats, crabs, octopus) to fixate, inspect and track visual objects of interests. A special type of eye movement, rapid eye movement, occurs during REM sleep. The eyes are the visual organs of the human body, and move using a system of six muscles. The retina, a specialised type of tissue containing photoreceptors, senses light. These specialised cells convert light into electrochemical signals. These signals travel along the optic nerve fibers to the brain, where they are interpreted as vision in the visual cortex. Primates and many other vertebrates use three types of voluntary eye movement to track objects of interest: smooth pursuit, vergence shifts and saccades. These types of movements appear to be initiated by a small cortical region in the brain's frontal lobe. This is corroborated by removal of the fr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eye Tracker
Eye tracking is the process of measuring either the point of gaze (where one is looking) or the motion of an eye relative to the head. An eye tracker is a device for measuring eye positions and eye movement. Eye trackers are used in research on the visual system, in psychology, in psycholinguistics, marketing, as an input device for human-computer interaction, and in product design. Eye trackers are also being increasingly used for rehabilitative and assistive applications (related,for instance, to control of wheel chairs, robotic arms and prostheses). There are a number of methods for measuring eye movement. The most popular variant uses video images from which the eye position is extracted. Other methods use search coils or are based on the electrooculogram. History In the 1800s, studies of eye movement were made using direct observations. For example, Louis Émile Javal observed in 1879 that reading does not involve a smooth sweeping of the eyes along the text, as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ferromagnetism
Ferromagnetism is a property of certain materials (such as iron) which results in a large observed magnetic permeability, and in many cases a large magnetic coercivity allowing the material to form a permanent magnet. Ferromagnetic materials are the familiar metals noticeably attracted to a magnet, a consequence of their large magnetic permeability. Magnetic permeability describes the induced magnetization of a material due to the presence of an ''external'' magnetic field, and it is this temporarily induced magnetization inside a steel plate, for instance, which accounts for its attraction to the permanent magnet. Whether or not that steel plate acquires a permanent magnetization itself, depends not only on the strength of the applied field, but on the so-called coercivity of that material, which varies greatly among ferromagnetic materials. In physics, several different types of material magnetism are distinguished. Ferromagnetism (along with the similar effect ferrimagnetis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Inductive Loop
An induction or inductive loop is an electromagnetic communication or detection system which uses a moving magnet or an alternating current to induce an electric current in a nearby wire. Induction loops are used for transmission and reception of communication signals, or for detection of metal objects in metal detectors or vehicle presence indicators. A common modern use for induction loops is to provide hearing assistance to hearing-aid users. Applications Vehicle detection Vehicle detection loops, called ''inductive-loop traffic detectors'', can detect vehicles passing or arriving at a certain point, for instance approaching a traffic light or in motorway traffic. An insulated, electrically conducting loop is installed in the pavement. The electronics unit applies alternating current electrical energy onto the wire loops at frequencies between 10 k Hz to 200 kHz, depending on the model. The inductive-loop system behaves as a tuned electrical circuit in which the lo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnetic Flux
In physics, specifically electromagnetism, the magnetic flux through a surface is the surface integral of the normal component of the magnetic field B over that surface. It is usually denoted or . The SI unit of magnetic flux is the weber (Wb; in derived units, volt–seconds), and the CGS unit is the maxwell. Magnetic flux is usually measured with a fluxmeter, which contains measuring coils and electronics, that evaluates the change of voltage in the measuring coils to calculate the measurement of magnetic flux. Description The magnetic interaction is described in terms of a vector field, where each point in space is associated with a vector that determines what force a moving charge would experience at that point (see Lorentz force). Since a vector field is quite difficult to visualize at first, in elementary physics one may instead visualize this field with field lines. The magnetic flux through some surface, in this simplified picture, is proportional to the num ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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