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What is degaussing? How can I degauss metallic components for my magnetometer setup?
General Magnetometer Info
Gretchen Sch...
3 years ago
9 Relevance
Degaussing is a Method by which magnetic domains in Metals or magnetic inclusions in other materials are randomized so that net magnetization is minimized. One tool do accomplish this is the “Bulk Tape Eraser” designed to erase data tapes. The Method works because the “Bulk Tape Eraser” generates an alternating electromagnetic field, which flips the magnetization of the magnetic domains in the material at 100 or 120 reversals per second (50 or 60 hertz). As the operator slowly removes the “Eraser” from the vicinity of the magnetized material, the magnetic domains of the material individually freeze in one orientation or the other, leaving the domains in a randomized orientation with minimal net magnetic effect. Degaussing with a Bulk Tape Eraser *The procedure is straight forward. Plug the Eraser into an extension cord or wall socket (the Eraser cord is usually short). Holding the object to be degaussed in one hand, depress the Eraser start button and move it towards the object. Once close to the object or section of material, begin moving the Eraser with a small circular motion and then increase the radius of the circle as you draw the Eraser away from the object. DO NOT STOP the Eraser closer than three feet from the object being degaussed or it will become strongly magnetized in one direction! If this happens accidentally, just redo the degaussing procedure over again starting from the beginning. *For larger objects, run the Eraser along tubing or struts in a circular motion to “bathe” the objects in an oscillating field. Be sure to cover the entire surface area of the object being degaussed. Then slowly withdraw the eraser (while still running) until it is at least 3 feet away. Then release the power switch. *The magnetometer can be used to check the sufficiency of the degaussing procedure. After degaussing, rotate the object close to an operating magnetometer to see if there is a response from the magnetometer. This is best done with a cesium magnetometer operated in gradient mode, but it can be done with a single sensor with one person watching the result and another moving the object Near the sensor. Degaussing Sensor Mount Degaussing Pack Frame Degaussing GPS Antenna Limitations of Degaussing with a Bulk Eraser Depth of penetration: The Bulk Tape Eraser can only randomize materials to a certain depth. This is due to the size of the gap in the degaussing unit. A small gap makes for a very large degaussing field at the gap (about 2000 gauss, or 200 million nanoteslas), but also for a very rapid falloff away from the gap. Bulk tape erasers are optimized to penetrate through the thickness of a typical video tape. This gives a typical depth of an inch (2.5 cm). Deeper objects may need to be degaussed using stronger degaussing fields. Degaussing through a conductive chassis: An additional problem occurs when the object being degaussed is covered by a conductive surface (such as a sheet of aluminum). The degaussing field will generate huge eddy currents in the conductive surface which will generate its own opposing magnetic field. This will be evident to the operator because the opposing field will cause the degausser to buzz loudly. This doesn’t hurt anything, but be aware that the degaussing field on the other side of the conductive surface will be attenuated by some amount, so it may take a longer amount of time or multiple passes to degauss the object. The Bulk Tape Eraser is a short duty cycle device. It varies a little from manufacturer to manufacturer, but typically it is rated for 1 minute on and 5 to 10 minutes off. Most have an internal thermal cutout that will shut it off if it overheats, and if tripped may take 20 minutes or more to cool down enough to reset. Frequently Asked Questions Why is degaussing needed? Degaussing misaligns magnetic domains so that there is no net permanent magnetization that would give an offset or heading error to magnetic field readings. Sensitive magnetometers such as those manufactured by Geometrics can be effected by Nearby materials that are not sufficiently magnetically randomized. Degaussing does not alter the induced magnetic moment of any material. A piece of steel, when degaussed, is still magnetic because it draws and concentrates the earth’s field through it. However, a degaussed piece of steel is much less magnetic than a permanently magnetized piece. How much effect does it have on magnetic signatures? Depending on the distance from the sensor to the magnetic object and the amount of magnetization, the effects can be very large -10’s of nanoTeslas. Many materials including brass, aluminum, fiberglass and other non-ferrous materials may have some ferrous materials in them naturally or acquired during the manufacturing process. Other materials such as ‘non-magnetic’ stainless steel are hugely magnetic when compared to the sensitivity of our magnetometers. Degaussing can decrease the magnetic effect of these materials by a factor of 10 or more. What should I degauss? The operator should degauss any Metallic object that is Near the sensor. By “near”, in general we Mean within 1 Meter but certainly those Metallic and non-metallic materials within a few centimeters of the sensor must be considered (this also includes the sensor itself, which could have minute magnetic inclusions in the sensor materials). This could also include GPS antennas, magnetometer cart assemblies (including brass fittings, bolts, clamps), buckles, eyeglasses, boots and parts of backpacks. We would also do occasional degaussing of the G-858 console and batteries. Will degaussing hurt anything? This is a tough question since it is impossible to imagine every conceivable system arrangement that could be subjected to degaussing. In all our experience we have never had any electronics device hurt by the degaussing process. This is because the induced voltages from the degausser are low, and the electronics components have a fairly high impedance at low voltages. It would be safer to degauss electronics while the power to the electronics is turned off in case the small induced voltages cause the device to operate incorrectly. It is always safe to degauss any of Geometrics’ manufactured equipment (including the sensor). On the other hand, here are some things to consider when degaussing some types of objects. Large conductive planes or rings will have large circulating currents induced in them by the degausser (but the voltages are still very small). This induced current will produce an opposing magnetic field that will fight the degaussing field – causing both the degausser and the conductive plane/loop to vibrate substantially. If the device being degaussed is sensitive to this vibration (intricate Mechanical workings and the like) then this is a possible route for causing some damage. Also, sometimes objects being degaussed have embedded magnets that are necessary for the device to operate properly. A good example is a device with a permanent magnet speaker inside. Generally it is hard to degauss a magnetically hard permanent magnet, but the degausser is strong enough to at least partially do the job. A partially degaussed speaker (or other object that requires a magnet to work right) isn’t going to work the same as before – so be aware. [Things that have magnets in them shouldn’t be used Near magnetometers anyway.] When to degauss and how often? We recommend that parts close to the sensor be degaussed before every major survey event. In other words on a weekly or monthly basis or before a new survey. Remnant magnetism or “Perm” can be “picked up” (domains realigned) when the materials are static in the earth’s magnetic field for a period of time. The amount of time required to acquire a “Perm” can be from days to weeks or months depending on the magnetic “hardness” of the materials. This is also known as the materials “susceptibility”, that is, susceptibility to being magnetized. Also, magnets are everywhere, and they can easily and unknowingly ‘perm’ up parts on or Near the sensor. Magnetic screwdrivers, for example, are great for holding steel screws on the end of the driver while starting them into a threaded hole, but they are bad news Near any magnetometer sensors.
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Iron Ore Exploration
General Magnetometer Info
Gretchen Sch...
3 years ago
5 Relevance
One of the primary uses of our magnetometers is mineral exploration. Iron ore is one of the easiest targets because of its magnetic properties. Because of this, magnetometer surveys are almost always part of the initial phase of any iron exploration program. Briefly stated, the exploration strategy is to use Portable magnetometers to Measure the magnetic field strength over the entire survey area by traversing it along many parallel survey lines with the magnetometer. This field work provides Measurements that are used to construct a magnetic anomaly map. Using this map, an economic geologist or geophysicist will infer the probable location of iron concentrations. Based on their assessment, drilling or sampling sites are chosen and, using the chemical assay of the samples, the iron ore reserves are calculated. You or your customer should be working with a geologist or geophysicist who is familiar with the region where the prospect area is located. Conducting a magnetometer survey and making a useful anomaly map are inexpensive activities as compared with survey data interpretation, sampling, and assay work. If your customer wants to learn more about magnetic survey practice, a good way to start is by downloading and reading the free Application Manual for Portable Magnetometers.
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RE: What is the MagArrow GPS accuracy in position/elevation/altitude?
Hardware
Magnetics SW
2 years ago
5 Relevance
Here are a few additional details relating to the Measurement of elevation: GNSS AccuracyAccuracy depends on multiple aspects of the GNSS system: among them are clock accuracy, atmospheric effects, and satellite geometry. Satellite geometry"Satellite geometry" refers to how the currently visible satellites are distributed in the sky - close to each other or scattered around. The best satellite geometry includes satellites that are Near the axes on which you hope to locate your receiver; for example, to locate your receiver on the East/West axis, it's helpful to have good reception from satellites low in the sky in the East and in the West. If you also have satellites that are low in the sky Near the South and North horizons, you will have good accuracy on the horizontal (latitude/longitude) plane. It's best to have satellites scattered around the sky, overhead as well as Near the horizon all around. HDOPMagArrow records HDOP, a standard Measure of satellite geometry's effect on horizontal (or latitude/longitude) accuracy. A smaller number (less than 1.0 is very good) indicates that the visible satellites are in good positions to contribute to accuracy. Vertical AccuracyThe reason that GNSS systems aren't as accurate on the vertical axis as on the horizontal axes is that no satellites are visible in a full half of that axis: the half that is below the horizon. Consequently, vertical accuracy is on average about half that of horizontal accuracy; calculated offset from true elevation is on average about twice that as on the horizontal axes. While on average HDOP can therefore be used to estimate VDOP (the similar Measurement of the effect of satellite geometry on the vertical axis), that estimate is only a rule of thumb; it is possible to have an excellent HDOP, reflecting very good horizontal satellite geometry, while having poor vertical satellite geometry. In those cases, good HDOP does not indicate good VDOP. Keeping in mind that possibility, a combination of good HDOP and many satellites in view usually indicates good VDOP. Practical effects Some data processing techniques (upward continuation, for example) can include elevation as an input. Customers who are considering using GNSS elevation in those techniques should conduct a careful analysis of their data and develop test routines to verify that all their data Meet the requirements of the technique and its application to a particular survey. Some customers who require very accurate elevation data incorporate LIDAR data and drone elevation data into their analyses.
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Differences Between our Standard Cesium Magnetometers and the SX Model
General Magnetometer Info
Gretchen Sch...
3 years ago
4 Relevance
Clarification regarding Geometrics standard magnetometers SX versions and the US Govt. export regulations In this brief review magnetometer specifications are given in terms of both nT/sq-rt-Hz RMS and in Peak-to-Peak (P-P) noise values as both forms are often used to describe instrument performance. The US Government specifies that an export license is required for magnetometers that have a sensitivity of better than (noise level less than) 0.02nT/sq-rt-Hz RMS. Obtaining an export license is not difficult but it does require approximately 6-8 weeks. Not all geophysical applications require export license sensitivity and so we offer SX models that have a noise floor of 0.02nT/sq-rt-Hz RMS. Compare this with our G-858 Magnetometer at 0.008nT/sq-rt-Hz RMS and our G-882 Marine Magnetometer at 0.004nT/sq-rt-Hz RMS. What does SX performance Mean in the survey results? When the sensor is deployed at some distance from the “source” such as in above the shoulder mounting for geological surveys (G-859SX) or at some distance (several Meters) from the seafloor for G-882SX surveys, the distance from the source provides some natural filtering of the Near surface response. This Means that surveys not focused on small target detection (20mm ordnance rounds) where the sensor is deployed very close to the ground (<1m), SX performance is more than adequate. Let us consider the G-858 man-portable model. Under low noise laboratory conditions at a sample rate of 10 samples per second, the G-858SX will show approximately 0.125 nT of noise (peak-to-peak) compared to a standard G-858 of about 0.05nT P-P. To understand the significance of this, the natural earth background noise due to geomagnetic micro-pulsations is about 0.02nT/sq-rt-Hz (about 0.125 nT peak-to-peak) at the quietest of times. Micro-pulsation amplitudes of 1 or 2 nT are common and, during active periods, they may be larger than 10 nT. Any magnetometer will produce a record of the combination of the background noise (micro-pulsations, diurnal drifts, etc) and its own internal noise. If the various noise components are not correlated with each other they will add as the square root of the sum of their squared amplitudes. In the case of the G-858SX, the combination of instrument noise and background micro-pulsations will be: √(0.125nT^2 + 0.125^2) = 0.18nT. For the standard G-858, this combination will be: √(0.05nT^2 + 0.125^2) = 0.13nT. That is, the SX model will exhibit about 30% more noise amplitude compared to the standard model if the atmospheric noise is typical. Unless the survey Measurements are referenced to a high performance base station magnetometer equipped with a very accurate clock, the user will not be able to detect any difference between SX and standard performance. If such base station data were available, the greatest difference that would be seen should be no greater than about 0.05nT P-P in the average peak-to-peak amplitude. Such small differences cannot be seen or even detected in the total field contour maps made for exploration surveys which are typically contoured at 1nT or more. It should be remembered that the amplitude of the geomagnetic micro-pulsations in the frequency range from 5hz to 10hz is not constant; i.e., at most times they will be greater than 0.125nT and occasionally less than this value. Their intensity is governed by the average intensity of the instantaneous global thunderstorm activity and sunspot activity.
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Thoughts on Attaching a Magnetometer to a non-Ferrous Sled or Frame
General Magnetometer Info
Gretchen Sch...
3 years ago
3 Relevance
Regarding the deployment of magnetometers on conductive sleds or carts Near power lines: Depending on the proximity of the magnetometer to the sled, elevated field readings may be observe under power lines are a result of AC induction in the aluminum sledge you are using as the tow vehicle. The reason there can be a DC effect from an AC source is due to 1) the strength and proximity of the induced AC source and 2) the orientation of the induced AC field relative to the Earth's field (DC). Our cesium-vapor magnetometers Measure the total local field continuously but report these Measurements periodically, e.g at 10, 1000 times per second. For each reporting period, both the AC and DC components of the total field are integrated to produce the Measurement result as a time average over the Measurement cycle. If your Measurements are being reported 10 times per second (10 hz sample rate) and the AC component of the field is 50 hz, then each Measurement will include exactly 5 AC cycles. This AC component will add to the DC component as a vector sum and the magnetometer will Measure the magnitude of the resultant vector. Note that the vector component of the 50 hz AC field that is parallel to the DC component will not contribute to Measurement results: for half of each AC cycle this field is greater than the DC field and for the other half of the cycle it is less than the DC field by an equal value. This is not the case for the AC vector component that is perpendicular to the DC field: it will be adding magnitude to the DC field on each 1/2 cycle to produce a half-wave-rectified wave form. Specifically, this rectified field will add to the DC field by an amount equal to about 35% of its peak-to-peak field strength in the direction perpendicular to the DC component. The AC rectification described above is only seen on close approach to very strong AC sources (high tension power lines). An aluminum sled can act as an indirect source of the AC fields: the radiated 50 hz field from the power lines is inducing 50 hz eddy currents in the sled and, if a magnetometer is in close proximity of the sled's aluminum plates, it will detect large AC field values. Note that surveying Near other large, planar conductors under the high tension power line can produce a similar effect. These would include Metal buildings, Metal fences, and pipelines. We recommend constructing magnetometer sleds from non-conductive materials. If this is cannot be done, then conducive materials should be kept as far from the sensor as is practical and the sled's construction should not include sheets of conductive materials. Any joints between conductive structural elements should be insulated as well. You can use the magnetometer itself to Measure the effect of the sled.
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Hammer Switch vs Trigger Geophone - Considerations
General Seismograph Info
Gretchen Sch...
3 years ago
3 Relevance
A seismograph with an active trigger input like the Geode Seismograph or ES-3000 Seismograph can be triggered many different ways. The most commonly used Methods are with a trigger switch or a trigger geophone. Typically a trigger switch (known as a hammer switch) is attached to the handle of a sledgehammer Near the striking end, so when the sledgehammer is hit against a striker plate to create an active source of energy, the piezoelectric crystal in the hammer switch is activated and the seismograph is triggered to record data along the preset parameters. A trigger geophone does this too, but it is placed Near the source itself, and is more commonly used with larger energy sources like a propelled energy generator. If the seismograph isn't triggering with either a hammer switch or a trigger geophone, then the signal may be weak, so turning up the sensitivity could be a workable solution. If the sensitivity is set too high in SCS then false triggers might be encountered. In most situations having the sensitivity set to the middle works best. Depending on where the trigger geophone is it, there may be a difference between when it is triggered and when a hammer switch would have triggered. Especially in soft ground the trigger geophone signal may be delayed. In general the hammer trigger is a more reliable timing device. The differences in trigger time when using a trigger geophone could be due to things like not striking the center of the plate or differences in the strength of the impact. More trigger circuit information: The seismograph can be triggered by shorting the two input pins A and B on the trigger connector of the seismograph. In fact, that is what the hammer switch does (contact closure device) when it impacts a striker plate. The inertia of the impact causes a momentary closure in the device, which in turn, triggers the Geode. There are no internal components that need to be added. Externally, you could construct trigger device or switch, if that is what you desire. If you were to Measure the pins on the Trigger connector on your seismograph (pin A +, pin B -) you would see about 5VDC. The trigger circuit will sense a contact closure or a pulse. The Geode trigger input is capacitively coupled, with a 2mS time constant, to the midpoint of a resistive voltage divider. The voltage difference between the two ends of the divider constitute a voltage "window", which size is set by the trigger sensitivity parameter and can range from essentially zero at the highest sensitivity, to about +/- 2.5V at the lowest sensitivity. The Geode triggers (if enabled) if and when the coupled signal exceeds the window, in either direction. The signal, after the capacitor, is clamped by diodes to the range between the trigger signal ground and +5VDC. The trigger detector output is disabled when the system is disarmed, during a parameter change, and during a shot, up to the trigger hold-off time after the end of the shot. The trigger hold-off time is a parameter set by the user. Preceding the coupling capacitor (i.e., essentially the node accessible at pin A of the external connector), there is a 3.3K-Ohm pull-up resistor to +5VDC (relative to pin B). Also a fast transient suppressor clamps the input at about +/-14VDC. It is advised that the DC + AC level of any voltage applied to pin A relative to pin B be kept within the range of +/-7V, giving some margin of safety. If a DC voltage somewhat less than +5VDC is applied when the connector is first mated, the instrument may trigger at that moment. But, subsequently, because of the capacitive coupling, it will trigger on the next positive or negative going pulse that exceeds the window level. If the duration of the applied voltage pulse is less than the record length + delay time + hold-off time, then the Geode will effectively be ready to trigger on the same edge of another similar pulse.
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What source should I use for seismic reflection surveying?
General Seismograph Info
Gretchen Sch...
3 years ago
3 Relevance
The best source for seismic reflection is not always the most practical. Parameters such as cost, size, access, surface materials, and depth of penetration must all be taken into account. As always, a sledgehammer always supplies the most bang for the buck when practical. If the ground surface is too soft for a sledgehammer, you might consider a downhole seisgun. Small explosives are ideal in terms of portability and power, but for obvious reasons are often not feasible. Less Portable sources like weight drops and vibrators should be considered when access allows and required depth of penetration exceeds that of a sledgehammer or seisgun. Although depth of penetration varies widely depending on the geology and cultural noise, you can expect to see somewhere in the range of 0.25 - 0.5 seconds with the latter two sources.
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Why you Need a Magnetometer Base Station
Application
Gretchen Sch...
3 years ago
3 Relevance
Your need of a magnetometer base station like the G-862RBS depends on the objective of the survey. If one is performing a geologic survey to investigate deep structure (exploration for mineral deposits, oil/gas, geology) then the wavelengths of the "target" body are typically “long” (long in Meters, therefore long in data acquisition time). The rate at which the Earth's natural magnetic field responds to interaction with the solar wind is also typically many seconds to minutes (diurnal variations). Since the geologic and diurnal variations are of similar wavelengths, a geologic mag survey usually requires a base station. Please read the introductory sections of the Applications Manual for Portable Magnetometers offered on our website for more details. If you are moving fast (fast in the sense of a brisk walk, ~1m/s) and looking for small targets (UXO, archaeological artifacts, environmental targets like drums, pipes, etc.) then you are “up and over” them in a matter of seconds and typically the earth’s field does not change in this time frame. So there is less need for a base station for these type surveys. Of course, it never hurts to have a base station running and if you are surveying over multiple days, having a reference station will allow easier “block leveling” of multiple day surveys.
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What is the Detection Range of a Magnetometer?
General Magnetometer Info
Gretchen Sch...
3 years ago
3 Relevance
This is a very common question and for the best answer, please read page 45 of the Applications Manual for Portable Magnetometers. To give an idea, the rule of thumb is that 1 ton of steel will give 1nT at 100 ft. The distortion caused by the steel in the earth’s field falls off as the cube with distance and is linear with mass. Therefore, at 50 ft, 250 lbs will give 1nT, at 25 ft 30 lbs will give 1nT, at 12 ft 4 lbs will give 1nT. Cables and pipelines fall off at somewhat a different rate (inverse square) so can be seen further for a given mass.
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Can a Magnetometer Detect Gold
General Magnetometer Info
Gretchen Sch...
3 years ago
3 Relevance
There are basically three types of "gold": low concentration disseminated gold in ore, placer gold deposits and solid gold such as that associated with treasure. Magnetometers are used to find disseminated gold by its association with mineralized zones which also contain magnetite or other magnetic minerals. Magnetometers are often used in conjunction with airborne electromagnetic surveys to find the conductive ore bodies. Placer gold is the type found in buried stream channels such as the gold which sparked the California gold-rush in 1849. Gold dust and magnetic minerals have been concentrated in river banks over thousands of years. Where there is gold there is often magnetite and therefore the magnetometer can be used to locate placer gold deposits. Gold treasure is a different story and being non-magnetic gold, silver, and other precious minerals are not directly detectable by the magnetometer. The magnetometer can only detect ferrous (iron or steel) objects. If the gold is stored in an iron box or has iron materials next to the gold (such as colonial ship ballast stones in the marine environment), there is the possibility of detecting the iron material. This is true for land and marine (sunken galleon) gold bullion. The vast majority of target search surveys are performed on a grid in a "lawn mower" back and forth manner to cover the area of interest. Lane spacing is dependent on target size (magnetic mass). At a sensor to target distance of 2 to 3 Meters there will need to be at least 1-2 kilograms of iron. This can produce a 1-2 nT anomaly that is detectable in a magnetically clean environment. The ideal environment would be in a plowed farm field or the bottom of the ocean away from human activity i.e., away from a port or harbor. You will probably not be able to detect this small of an anomaly in a city or port location. The more iron mass there is, the better the chance of detecting it. Training to use the magnetometer can take 1-2 days depending on experience with setting up computerized survey equipment and a GPS. Processing the magnetic data requires several days of training and would require a geophysical background to interpret the final maps. We provide free software to make maps and estimate the target depth of burial (inversion). If you are unfamiliar with this procedure, we would recommend that you find a local geotechnical firm to look at the data to determine if there are anomalies that should be investigated further. Remembering that non-ferrous materials do not cause anomalies (gold, silver, copper, brass, aluminum, gems) you will be looking for anomalies either associated with the container OR associated with ground disturbance (i.e., gravesite). In this way some anomalies can be detected where there has been an excavation such as a gravesite. In order to understand the process more fully, we strongly suggest that you download and read the Applications Manual for Portable Magnetometers. Other additional resources are available. Understanding how the magnetometer functions and how the earth’s field responds to distortions due to ferrous materials will help you make good decisions about how to interpret and use the data to direct recovery or exploration efforts.
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Use and Care of G-857/G-858/G-859 Batteries
Hardware
Gretchen Sch...
3 years ago
3 Relevance
The batteries used in the Portable magnetometer instruments are lead-acid gelled electrolyte batteries. The choice of this type of battery was dictated by their non-magnetic internal construction. We “magnetically compensate” these batteries to further reduce their magnetic signature. We do this with bucking coils which are mounted against the battery surfaces and then an external wrap applied. The batteries should be charged using the charger furnished with the instrument. These chargers are fully automatic and designed to do the best job of charging and maintaining the batteries for long life. All of the chargers are equipped with lights indicating when the battery is being charged and when the charging cycle is completed. The battery packs will provide the most operating cycles when they are fully charged after each use. The number of operating cycles can vary from 250 cycles to above 1000 cycles depending on how deep the discharge was and how soon the battery is charged after use. A 30% discharge per cycle may result in a lifetime of 1000 cycles or more, whereas a 100% discharge per cycle can result in only 250 cycles. As a rule the magnetometer will shut down when the battery is discharged to about 20% of full voltage. This is to ensure proper shutdown of the instrument. It is very important to recharge the battery as soon as possible after use so the maximum life can be expected from the pack. If the discharged pack is left to charge “when we get back from the field” the pack can suffer from “sulphation”. This is a high-resistance buildup in the battery which may render the battery unusable. If a battery of this type must be stored for an extended period, it must be stored in a fully-charged condition. If such a battery is stored discharged and subject to below-freezing conditions, it is likely to freeze and be subsequently unusable. All Lead-Acid batteries must be maintained when in storage. This Means that the user must recharge each pack at least once a month. Lead Acid batteries will self-discharge due to stray internal resistances, causing very small drain currents. Thus the maintenance requirement for monthly recharging is critical to long battery life. Do not leave the charger on all the time during storage. Also it is very important to use discharge the batteries on a regular basis otherwise the lifespan will be severely shortened. For more information contact our Support Department.
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Magnetometer Exploration Depth
General Magnetometer Info
Gretchen Sch...
3 years ago
3 Relevance
In a general sense, the exploration depth of a magnetometer is unlimited. It is certainly sensitive to the Earth's field and this is generated in the Earth's Core, some 5000 km beneath our feet. But for practical purposes, the depth of exploration is determined from survey results by the spatial width of the magnetic field anomaly as observed at the Earth's surface. For discrete objects, the depth of exploration is nominally 1/2 of the width of the magnetic anomaly. This topic is discussed in our Portable Magnetometer Operation Manual. This Manual covers many topics related to survey design and interpretation including exploration depth. As you will see, survey design will have a large influence on the depth of investigation.
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How Far Can a Magnetometer 'See'?
General Magnetometer Info
Gretchen Sch...
3 years ago
3 Relevance
Total field magnetometers like the optically pumped cesium magnetometer are passive devices, they do not send out waves or pulses. They Measure distortions in the earth’s normally homogenous magnetic field and can sense distortions due to ferrous objects at great distances. The basic rule of thumb is that one ton (1000 Kg) of steel or iron will give us a 1nT anomaly at 100 ft. or 30m. Since the amount of distortion falls off as the cube with distance (compare a Metal detector which falls off as the inverse 6th power!) and is linear with mass, every time we cut the distance in half, we can see 1/8th the mass. Therefore, we can sense 250 lbs. (100kg) at 50 feet (15m), or 30lbs (15kg) at 25 feet (8m), or 4lbs (2kg) at 12 feet (4m). However this is not the whole story. The factors given above are for induced magnetic fields only. Many targets also have remnant or permanent magnetic effects (meaning they have become magnetized either in production or by the earth’s field) and can therefore have larger anomalies by a factor of 3 or 5 or more. Also many hollow objects like barrels or other tubular structures appear as though they are solid due to self-shielding from the earth’s field, and thus have much larger anomalies than their mass would predict alone. Pipes fall off as the inverse square and are thus detectable at even greater distances. Please see our Applications Manual for Portable Magnetometers for more information.
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Integrating log data in SeisImager (SPT, DCP, N-Value, Soil Logs)
SeisImager Software
Kolby Pedrie
1 year ago
2 Relevance
The Drawing Tool Menu provides functionality for integrating log file datasets—such as N-value, boring, soil, and DCP logs—with velocity profiles. Below is an example of a boring data log .txt file that includes a soil column: 0.45 8 1.45 8 2.45 1 3.45 5 4.45 5 5.45 31 6.45 21 7.45 23 8.45 31 9.45 22 10.45 8 11.45 11 12.45 12 13.45 8 14.45 3 15.45 32 16.45 33 17.45 42 4.9 C Clay 17.45 G Gravel Log files can be loaded with or without headers. To load a log file, navigate to the Drawing Tool Menu. After loading, use the Select Tool (represented by the arrow icon in the top toolbar) to interact with the objects in the plot. Attachment : image018.png The Select Tool allows you to select and edit objects such as logs. To modify a log, double-click Near the base of the comment line associated with the log. A configuration Menu will appear, where you can specify the data type—N-value, Line, or Soil Column—and adjust axis settings and labels as needed.
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RE: Error 56 occurred at TCP Open Connection in MagViewMFAM_V1_1_3_2.vi
Application
Kuldeep Dhim...
2 years ago
2 Relevance
and also there is no light blinking in the Ethernet status Near the Ethernet port of MFAM dev kit.
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