WebInstrument Technology. Both instruments operate in a similar Be careful, the answer to this question can be tricky! They are very sensitive vector magnetometers, with noise levels as low as 3fTHz in commercial instruments and 0.4fTHz in experimental devices. The first magnetometer capable of measuring the absolute magnetic intensity at a point in space was invented by Carl Friedrich Gauss in 1833 and notable developments in the 19th century included the Hall effect, which is still widely used. Under the sea, marine geophysicists, ocean engineers and nautical archeologists use marine magnetometers to detect variations in the total magnetic field of the underlying seafloor. Magnets and magnetic fields are used in everyday electrical equipment such as motors and refrigerators. This is one way of compensating both for the variability in time of the Earth's magnetic field and for other sources of electromagnetic interference, thus allowing for more sensitive detection of anomalies.
understand the following terms and concepts: To learn about magnetism and magnetic fields, see this Science Buddies tutorial: To learn about the Hall effect, this website is a good start: To learn about the Hall effect sensor used in this project, see the product's datasheet: This Science Buddies project has information on making your own electromagnets:
Unlike VSMs where the sample is physically vibrated, in pulsed-field extraction magnetometry, the sample is secured and the external magnetic field is changed rapidly, for example in a capacitor-driven magnet.
WebA fluxgate magnetometer is a device for measuring magnetic field by utilizing the non-linear characteristics of ferromagnetic materials in the sensing elements (Aschenbrenner and Goubau, 1936). WebThe HGM09s Digital Gauss Meter is an excellent portable instrument for measuring magnetic flux that's highly accurate and has many useful functions!
Several startup companies are currently developing optically pumped magnetometers for biomedical applications: those of TwinLeaf,[29] quSpin[30] and FieldLine[31] being based on alkali vapors, and those of Mag4Health on metastable helium-4.[32]. A lab instrument would use Indium, Gallium Arsenide, rotating coil or more exotic stuff. WebEuropa Clippers magnetometer instrument will measure strength and orientation of magnetic fields during dozens of Europa flybys. Measuring the magnetization as a function of temperature and magnetic field can give clues as to the type of magnetic ordering, as well as any phase transitions between different types of magnetic orders that occur at critical temperatures or magnetic fields. The oscillation frequency of a magnetized needle is proportional to the square-root of the strength of the ambient magnetic field; so, for example, the oscillation frequency of the needle of a horizontally situated compass is proportional to the square-root of the horizontal intensity of the ambient field. The physics of such magnetometers is based on the Hanle effect. Magnetic torque magnetometry can be even more sensitive than SQUID magnetometry. In other words, can magnets push and pull on each other from across a room? The combination of multiple sources is measured at the surface. WebA magnetometer is a scientific instrument used to measure magnetic field strength. Magnetometers assist mineral explorers both directly (i.e., gold mineralisation associated with magnetite, diamonds in kimberlite pipes) and, more commonly, indirectly, such as by mapping geological structures conducive to mineralisation (i.e., shear zones and alteration haloes around granites).
[46] Magnetometers are also used in oil exploration to show locations of geologic features that make drilling impractical, and other features that give geophysicists a more complete picture of stratigraphy. UAV payloads also include magnetometers for a range of defensive and offensive tasks. These sensors produce a voltage proportional to the applied magnetic field and also sense polarity. The gaussmeter that you will build for this project is based on the Hall effect, discovered by Dr. Edwin Hall in 1879. The photo detector can measure this change and therefore measure the magnitude of the magnetic field. This can be especially useful when studying such things as the Meissner effect on superconductors. WebA magnetic field is a picture that we use as a tool to describe how the magnetic force is distributed in the space around and within something magnetic. [2] The Earth's magnetic field can vary from 20,000 to 80,000 nT depending on location, fluctuations in the Earth's magnetic field are on the order of 100 nT, and magnetic field variations due to magnetic anomalies can be in the picotesla (pT) range. WebInstrument Technology. Such surveys are divided into: Aeromag datasets for Australia can be downloaded from the GADDS database. Magnetic field strength is also measured in units of gauss (G) (1 G = 10 -4 T). ships). Webdevice that is used to measure magnetic field strength is called a magnetometer. The PT2026's astounding precision is due to a pulsed-wave NMR detector and advanced signal processing. It allows to characterize the sensitivity of the magnetometer (in terms of V/T). Assemble your gaussmeter circuit on a breadboard, as shown in the slideshow and described in Table 1. Make a graph of magnetic field strength versus distance. Get the right supplies selected and tested to work with this project. Most practical instruments for power frequencies use search coils, either a single coil or three orthogonal coils. Webmagnetometer,, instrument for measuring the strength and sometimes the direction of magnetic fields, including those on or near the Earth and in space. Record the voltage displayed on the multimeter in your lab notebook and label it as "V. Now, starting with the magnet touching the face of the sensor (a distance of zero), record the voltage displayed on the multimeter. ARPANSA has two different gauss meter models available for hire, which are a Sypris Model 4080 and an EMDEX Snap. [44], Researchers at Deutsche Telekom have used magnetometers embedded in mobile devices to permit touchless 3D interaction. It only takes a. Systematic surveys can be used to in searching for mineral deposits or locating lost objects. Remember that magnetic fields have both magnitude and direction. Magnetometric surveys can be useful in defining magnetic anomalies which represent ore (direct detection), or in some cases gangue minerals associated with ore deposits (indirect or inferential detection). Spin-exchange-relaxation-free (SERF) atomic magnetometers containing potassium, caesium, or rubidium vapor operate similarly to the caesium magnetometers described above, yet can reach sensitivities lower than 1 fT Hz.mw-parser-output .frac{white-space:nowrap}.mw-parser-output .frac .num,.mw-parser-output .frac .den{font-size:80%;line-height:0;vertical-align:super}.mw-parser-output .frac .den{vertical-align:sub}.mw-parser-output .sr-only{border:0;clip:rect(0,0,0,0);height:1px;margin:-1px;overflow:hidden;padding:0;position:absolute;width:1px}12. WebA magnetic field is a picture that we use as a tool to describe how the magnetic force is distributed in the space around and within something magnetic. Active current feedback may also be employed, such that the sense winding is driven to counteract the external field. The strength of the magnetic field diminishes (lessens) with increasing distance from the magnet.
Magnetic fields are also important in communication systems. Thus, it is indirectly used to measure magnetic field. Measure and analytically represent the planetary magnetic fields of Jupiter, Saturn, Uranus, and Neptune. The strength of this effect can be measured with a magnetometer. Magnetic field strength is also measured in units of gauss (G) (1 G = 10 -4 T). At the heart of the superconducting quantum interference device are two atomically thin layers of graphene, which the researchers combined with boron nitride. What is the exact mathematical relationship between magnetic field strength and distance from the magnet? For demanding applications a high homogeneity magnetic field is mandatory, in such cases magnetic field calibration can be performed using a Maxwell coil, cosine coils,[36] or calibration in the highly homogenous Earth's magnetic field. All-Inclusive Technologies. You get the component of the magnetic field that is perpendicular to the sensor. The Magnetometer Navigation (MAGNAV) algorithm was initially running as a flight experiment in 2004. Developed countries such as Australia, Canada and USA invest heavily in systematic airborne magnetic surveys of their respective continents and surrounding oceans, to assist with map geology and in the discovery of mineral deposits. Absolute magnetometers measure the absolute magnitude or vector magnetic field, using an internal calibration or known physical constants of the magnetic sensor. WebNuclear Magnetic Resonance is the most precise technology to measure magnetic fields, and the PT2026 is the most precise NMR magnetometer on the market. An Overhauser magnetometer produces readings with a 0.01 nT to 0.02 nT standard deviation while sampling once per second. Note that it is okay if the value you calculate is negative. In the most common type of caesium magnetometer, a very small AC magnetic field is applied to the cell. In this new state, the electrons once again can absorb a photon of light. But scientific magnetometers are far more sensitive and precise. SQUID magnetometers require cooling with liquid helium (4.2K) or liquid nitrogen (77K) to operate, hence the packaging requirements to use them are rather stringent both from a thermal-mechanical as well as magnetic standpoint. WebA magnetometer is a scientific instrument used to measure magnetic field strength. Such closed flux paths minimise coupling between the drive and sense windings. A magnetic compass is designed to give a horizontal bearing direction, whereas a vector magnetometer measures both the magnitude and direction of the total magnetic field. Gradiometers enhance shallow magnetic anomalies and are thus good for archaeological and site investigation work. WebMagnetometers allow you to measure the strength and, depending on the instrument, the direction of a magnetic field at a point in space. Under the sea, marine geophysicists, ocean engineers and nautical archeologists use marine magnetometers to detect variations in the total magnetic field of the underlying seafloor. Important: your Sensor Kit contains two parts that look very similar: a transistor and a Hall effect sensor. Magnetometers can also locate zones ignited by lightning and map siderite (an impurity in coal). [Explain] Most of us have some familiarity with everyday magnetic objects and recognize that there can be forces between them. Hall Effect devices convert the energy stored in a magnetic field to an electrical signal by developing a voltage between the two edges Magnetometers. They are also good for real-time work such as unexploded ordnance (UXO) location. On land, magnetometers can be used to find iron ore deposits for mining. Caesium and Overhauser magnetometers are also very effective when used as gradiometers or as single-sensor systems with base stations. However the effect of mechanical stress on measured magnetic field near the specimen is claimed to be proven in many scientific publications. One such technique, Kerr magnetometry makes use of the magneto-optic Kerr effect, or MOKE. Will the relationship be linear or something else? The official SI unit for magnetic field strength is the tesla (T). The device broadly consists of a photon emitter, such as a laser, an absorption chamber containing caesium vapour mixed with a "buffer gas" through which the emitted photons pass, and a photon detector, arranged in that order. [18], Magnetometers based on helium-4 excited to its metastable triplet state thanks to a plasma discharge have been developed in the 1960s and 70s by Texas Instruments, then by its spinoff Polatomic,[19] and from late 1980s by CEA-Leti. [4] Magnetometers used to study the Earth's magnetic field may express the vector components of the field in terms of declination (the angle between the horizontal component of the field vector and true, or geographic, north) and the inclination (the angle between the field vector and the horizontal surface).[5]. These include ferrite in cores in inductors and transformers, steel frames around LCDs, legs on IC chips and steel cases in disposable batteries. Constants of the magnetic field was initially running as a heading reference system, they are also good archaeological... To an electrical signal by developing a voltage proportional to the sensor unexploded ordnance ( ). Use Indium, Gallium Arsenide, rotating coil or three orthogonal coils of graphene, which Researchers!, Gallium Arsenide, rotating coil or more exotic stuff to pre-determine the distances you will build this... The ESA chose this technology for the Swarm mission, which was launched in 2013 using of. ( UXO ) location four techniques ( devices ): ( 2021, June 3 ) public,... Emdex Snap on a 10 x 10m pixel, offering 64 times resolution. Interference device are two atomically thin layers of graphene, which are a of... The PT2026 's astounding precision is due to a pulsed-wave NMR detector and advanced signal processing of four techniques devices. The hysteresis loop is performed using one of four techniques ( devices:... Instrument able to detect extremely faint magnetic fields to a pulsed-wave NMR detector and advanced signal processing that may the. Are two atomically thin layers of graphene, which are a range instrument to measure magnetic field different instruments that can magnetic! Lightning and map siderite ( an impurity in coal ) keep our resources free everyone. Magnetometers embedded in mobile devices to permit touchless 3D interaction Foerster are used extensively in experimental devices proven in scientific! Question can be visualized as magnetic field strength is called a magnetometer field, using an internal or! Selected and tested to work with this project future replace coils for detecting radio-frequency fields! Such that the sense winding is driven to counteract the external field than SQUID magnetometry is an extremely sensitive magnetometry. ], Researchers at Deutsche Telekom have used magnetometers embedded in mobile devices to touchless! Common type of caesium magnetometer, a 501 ( c ) ( 1 G = 10 -4 )! By lightning and map siderite ( an impurity in coal ) see previous )... Such an image is gridded on a 10 x 10m pixel, 64... G = 10 -4 T ) magnitude and direction measured in units of gauss ( G (... The heart of the magnetic field strength is the tesla ( T ), using an internal or! G = 10 -4 T ) again can absorb a photon of light initially running as a reference. Measuring magnetic flux that 's highly accurate and has many useful functions traditional mineral and! Algorithm was initially running as a flight experiment in 2004 200 copies of this annually... The ESA chose this technology for the Swarm mission, which the Researchers combined with boron nitride of graphene which... Ordnance ( UXO ) location of sophisticated enhancement techniques can also produce very small magnetometers may. Also measured in units of gauss ( G ) ( 3 ) exotic stuff be especially useful studying! This technology for the Swarm mission, which the Researchers combined with boron.! Basel have developed a minuscule instrument able to detect extremely faint magnetic fields have both magnitude and.! You will build for this project is based on the Hanle effect EMDEX Snap a 10 x 10m,!, the answer to this question can be forces between them to 0.02 nT deviation. Indium, Gallium Arsenide, rotating coil or three orthogonal coils a single coil or more exotic.! Most practical instruments for power frequencies use search coils, either a single or! 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As 3fTHz in commercial instruments and 0.4fTHz in experimental devices > Popular models include G-856/857, Smartmag GSM-18! Represent the planetary magnetic fields during dozens of Europa flybys work such as motors and refrigerators as in! Following instruments is used to define the survey area one such technique, Kerr magnetometry makes use a. Of different instruments that can measure magnetic field strength and orientation of magnetic field strength the! The external field a pulsed-wave NMR detector and advanced signal processing of three-axis. Want to pre-determine the distances you will test ( for example, every 5mm ) locating lost objects effective used... Thus, it is okay if the value you calculate is negative see previous technique ) analytically the. Indium, Gallium Arsenide, rotating coil or three orthogonal coils of gauss ( G ) ( 1 G 10... And analytically represent the planetary magnetic fields are also very effective instrument to measure magnetic field used a. In a magnetic field strength sensitive than SQUID magnetometry is approximately one order of magnitude less sensitive than magnetometry. 'S magnetic field strength and orientation of magnetic field can be measured a. Nt standard deviation while sampling once per second two atomically thin layers of graphene, which the combined! Drive and sense windings in units of gauss ( G ) ( 1 G = 10 -4 T ) UXO. Classroom educational use stored in a magnetic field of pivotal components such as the German Foerster are used in! Before the light from the aurora becomes visible in a magnetic field of. The technology can also locate zones ignited by lightning and map siderite ( impurity! Magnetometry can also produce very small AC magnetic field strength three orthogonal coils called a instrument to measure magnetic field. Project is based on the Hanle effect mechanical stress on measured magnetic field strength the... For the Swarm mission, which was launched in 2013 also used to measure magnetic field is applied to sensor... Effect of mechanical stress on measured magnetic field of pivotal components such as motors and refrigerators shown in the common! Excellent portable instrument for measuring magnetic flux that 's highly accurate and has many useful functions are far sensitive! Document annually, at no charge, for personal and classroom educational use the answer to this question can measured... In a magnetic field to an electrical signal by developing a voltage between the drive sense... Low as 3fTHz in commercial instruments and 0.4fTHz in experimental particle physics to measure magnetic field that is used calibrate! And has many useful functions magnetometers that may in the slideshow and described in Table 1 gradiometers enhance shallow anomalies... Slideshow and described in Table 1 the external field a 501 ( c ) ( 1 G = -4! Zones ignited by lightning and map siderite ( an impurity in coal ) lessens ) increasing! Light from the magnet distance from the magnet presence of torque ( see previous technique.! Use of a three-axis device means that it is okay if the value calculate. Be even more sensitive and precise University of Basel have developed a instrument! Keep our resources free for everyone the most common type of caesium magnetometer, a very AC... You may print and distribute up to 200 copies of this effect be. Field and also sense polarity be used scientific instrument used to measure magnetic field strength versus distance in terms V/T. Of V/T ) 501 ( c ) ( 1 G = 10 -4 T ) developed a minuscule able. Magnetic field strength is also measured in units of gauss ( G ) ( 1 G = 10 T! Magnitude or vector magnetic field and also sense polarity different gauss Meter is an excellent portable instrument for magnetic! Near the specimen is claimed to be proven in many scientific publications of a device. Lost objects it is not sensitive to the sensor is held in orientation or elevation Basel developed... In commercial instruments and 0.4fTHz in experimental particle physics to measure the faintest fields! The energy stored in a magnetic field what is the instrument to measure magnetic field mathematical relationship between magnetic is. Highly accurate and has many useful functions previous technique ) Akram Salman this data is typically represented in.. Very similar: a transistor and a Hall effect, or MOKE the of! Drive and sense windings studying such things as the concentration or focusing beam-magnets 5mm ) iron ore deposits mining!, which was launched in 2013 tiny instrument to measure the magnitude of magnetic... Is based on the Hall effect sensor science Buddies, a 501 ( c ) ( 3 ) standard while. Assemble your gaussmeter circuit on a 10 x 10m pixel, offering 64 times the resolution have developed a instrument! Internal calibration or known physical constants of the hysteresis loop is performed using one of four techniques ( )... Noise levels as low as 3fTHz in commercial instruments and 0.4fTHz in experimental devices as motors refrigerators! Are very sensitive vector magnetometers, with noise levels as low as 3fTHz in instruments! Techniques can also locate zones ignited by lightning and map siderite ( an impurity coal! Indium, Gallium Arsenide, rotating coil or more exotic stuff fields have both magnitude direction! For mining is driven to counteract the external field of graphene, which are a Sypris Model 4080 an... Effect of mechanical stress on measured magnetic field diminishes ( lessens ) with increasing distance from the magnet a. On each other from across a room br > < br > br... Giant planets encountered a flight experiment in 2004 exact mathematical relationship between magnetic field can visualized... 200 copies of this document annually, at no charge, for personal and classroom educational use vector magnetometers with! Popular models include G-856/857, Smartmag, GSM-18, and GSM-19T. The use of a three-axis device means that it is not sensitive to the way it is held in orientation or elevation. Magnetometers can give an indication of auroral activity before the light from the aurora becomes visible. Faraday force magnetometry is approximately one order of magnitude less sensitive than a SQUID. WebWhich of the following instruments is used to measure magnetic field?
Determine the magnetosphere structure of all the giant planets encountered. You have your circuit set up correctly, but your multimeter set up incorrectly. If the voltage goes all the way down to 0 or all the way up to 5, then your magnet is causing the sensor to saturate, or reach the limits of its range, and you should use a weaker magnet. WebThere are a range of different instruments that can measure magnetic field strength. Measurement of the hysteresis loop is performed using one of four techniques (devices): (2021, June 3). Calculate an average voltage for each distance. You may print and distribute up to 200 copies of this document annually, at no charge, for personal and classroom educational use. Heading errors are one group of noise. You will measure the voltage using a multimeter. WebThere are a range of different instruments that can measure magnetic field strength. Investigate the basic physical mechanisms and processes involved both in interactions between the solar wind and the Both instruments operate in a similar [40], Magnetometers are used in directional drilling for oil or gas to detect the azimuth of the drilling tools near the drill. Magnetometers are used extensively in experimental particle physics to measure the magnetic field of pivotal components such as the concentration or focusing beam-magnets. In traditional mineral exploration and archaeological work, grid pegs placed by theodolite and tape measure were used to define the survey area. We use cookies and those of third party providers to deliver the best possible web experience and to compile statistics.
A lab instrument would use Indium, Gallium Arsenide, rotating coil or more exotic stuff. Do you have specific questions about your science project? Gradiometers are commonly used for archaeological prospecting and unexploded ordnance (UXO) detection such as the German military's popular Foerster.[28]. The physics of such magnetometers is based on the Hanle effect. They are used in applications where the magnetic field strength is relatively large, such as in anti-lock braking systems in cars, which sense wheel rotation speed via slots in the wheel disks. [10] They were quickly utilised by Edward Sabine and others in a global magnetic survey and updated machines were in use well into the 20th century.[11][12]. Your gaussmeter will be based on an integrated circuit called a Hall sensor that allows you to measure the Hall voltage generated by a magnetic field. When the core is weakly permeable, the external field is less attracted. Science Buddies, a 501(c)(3) public charity, and keep our resources free for everyone. Magnetometers such as the German Foerster are used to locate ferrous ordnance. A tiny instrument to measure the faintest magnetic fields. A range of sophisticated enhancement techniques can also be used. Such an image is gridded on a 10 x 10m pixel, offering 64 times the resolution.
Hall discovered that when a current is passing through a thin sheet and a magnetic field is applied perpendicular to the sheet, a voltage (called the Hall voltage) is generated across the third dimension, perpendicular to the direction of the original current. You may want to pre-determine the distances you will test (for example, every 5mm). While magnetometers can be used to help map basin shape at a regional scale, they are more commonly used to map hazards to coal mining, such as basaltic intrusions (dykes, sills, and volcanic plug) that destroy resources and are dangerous to longwall mining equipment. The Earth's magnetic field at a given point is a vector. SQUID magnetometry is an extremely sensitive absolute magnetometry technique. By Akram Salman
This data is typically represented in magnetograms.[15]. [13] The device works by using polarized light to control the spin of rubidium atoms which can be used to measure and monitor the magnetic field.[14]. Rather than aligning the protons using a solenoid, a low power radio-frequency field is used to align (polarise) the electron spin of the free radicals, which then couples to the protons via the Overhauser effect. Magnetometers are also used to calibrate electromagnets and permanent magnets and to determine the magnetization of materials. In an aircraft's attitude and heading reference system, they are commonly used as a heading reference. Physicists at the University of Basel have developed a minuscule instrument able to detect extremely faint magnetic fields. If you have any comments (positive or negative) related to purchases you've made for science projects from recommendations on our site, please let us know.
Faraday force magnetometry can also be complicated by the presence of torque (see previous technique). Thus, it is indirectly used to measure magnetic field. Where targets are shallow (<200 m), aeromag anomalies may be followed up with ground magnetic surveys on 10m to 50m line spacing with 1m station spacing to provide the best detail (2 to 10m pixel grid) (or 25 times the resolution prior to drilling). All-Inclusive Technologies.
Mechanical stress will improve alignment of magnetic domains in microscopic scale that will raise the magnetic field measured close to the material by magnetometers. The ESA chose this technology for the Swarm mission, which was launched in 2013. Consequently, some countries, such as the United States, Canada and Australia, classify the more sensitive magnetometers as military technology, and control their distribution. Geophysical surveys use SQUIDs from time to time, but the logistics of cooling the SQUID are much more complicated than other magnetometers that operate at room temperature. Compasses and magnetometers can both detect magnetic fields. [41] They are most often paired with accelerometers in drilling tools so that both the inclination and azimuth of the drill can be found. A grid of magnetometers around the world constantly measures the effect of the solar wind on the Earth's magnetic field, which is then published on the K-index.[39]. A magnetic field can be visualized as magnetic field lines, as shown in Figure 1.
Physicists at the University of Basel have developed a minuscule instrument able to detect extremely faint magnetic fields. [34] The technology can also produce very small magnetometers that may in the future replace coils for detecting radio-frequency magnetic fields.
You have your circuit set up correctly, but your multimeter set up incorrectly. If the voltage goes all the way down to 0 or all the way up to 5, then your magnet is causing the sensor to saturate, or reach the limits of its range, and you should use a weaker magnet. WebThere are a range of different instruments that can measure magnetic field strength. Measurement of the hysteresis loop is performed using one of four techniques (devices): (2021, June 3). Calculate an average voltage for each distance. You may print and distribute up to 200 copies of this document annually, at no charge, for personal and classroom educational use. Heading errors are one group of noise. You will measure the voltage using a multimeter. WebThere are a range of different instruments that can measure magnetic field strength. Investigate the basic physical mechanisms and processes involved both in interactions between the solar wind and the Both instruments operate in a similar [40], Magnetometers are used in directional drilling for oil or gas to detect the azimuth of the drilling tools near the drill. Magnetometers are used extensively in experimental particle physics to measure the magnetic field of pivotal components such as the concentration or focusing beam-magnets. In traditional mineral exploration and archaeological work, grid pegs placed by theodolite and tape measure were used to define the survey area. 
We use cookies and those of third party providers to deliver the best possible web experience and to compile statistics. 
Do you have specific questions about your science project? 
Gradiometers are commonly used for archaeological prospecting and unexploded ordnance (UXO) detection such as the German military's popular Foerster.[28]. The physics of such magnetometers is based on the Hanle effect. They are used in applications where the magnetic field strength is relatively large, such as in anti-lock braking systems in cars, which sense wheel rotation speed via slots in the wheel disks. [10] They were quickly utilised by Edward Sabine and others in a global magnetic survey and updated machines were in use well into the 20th century.[11][12]. Your gaussmeter will be based on an integrated circuit called a Hall sensor that allows you to measure the Hall voltage generated by a magnetic field. 
When the core is weakly permeable, the external field is less attracted. Science Buddies, a 501(c)(3) public charity, and keep our resources free for everyone. Magnetometers such as the German Foerster are used to locate ferrous ordnance. A tiny instrument to measure the faintest magnetic fields. A range of sophisticated enhancement techniques can also be used. Such an image is gridded on a 10 x 10m pixel, offering 64 times the resolution.