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| # | Post Title | Result Info | Date | User | Forum |
| Battery percentage and status | 1 Relevance | 2 years ago | Magnetics SW | MagEX | |
| Overview The MagEx instrument And the MagNav app both display information about the state of the instrument's battery. Battery state And reporting exist in bands according to percentage of remaining battery capacity: 30% or higher:The instrument has good remaining capacity.The LED on the instrument's power switch glows a solid green.MagNav displays the battery percentage or voltage in black text on a white background. Between 20% And 30%:The instrument has capacity to survey for additional time, but if you will be surveying a significant amount more, start thinking about changing the battery.The LED on the power switch is blue.MagNav displays the battery percentage with a blue background. Between 5% And 20%:You can continue to survey, but the battery is running low And you should consider changing the battery soon.The LED on the power switch is red.MagNav displays the battery percentage with a red background, And periodically notifies you that the battery is running low. Below 5%:The battery is running low, And the instrument may turn off at any time in order to preserve battery health. You should change the battery as soon as possible. Temperature-related effects:Battery performance also changes as the temperature of the battery changes; as the temperature of a battery falls, the voltage it supplies also decreases, And the total energysupplied by the battery decreases. This means that in cold weather a battery will not last as long as in hot weather. The battery percentages reported in the instrument are adjusted for the effect of temperature; at a given battery voltage a cold battery will display a higher percentage than a warm battery will report. The effects of colder temperatures are not normally permanent; as a battery warms up, its output voltage And energy return to higher levels. Notes about the calculation:The MagEx instrument includes 2 batteries, And each battery includes 3 separate cells. Battery percentages are calculated from only one battery in the instrument - either the single battery if only one is connected, or from the better battery if two batteries are connected. Reported battery percentage is an estimate, based on measurements of the behavior of healthy batteries in instruments in the field And in the lab. Battery performance may change as a battery ages And as the temperature changes. The best practice for batteries is to use 2 healthy, fully charged batteries, And replace them both when the percentage falls below 20%. | |||||
| Is it possible to extend the cables between the MFAM sensors and module? | 1 Relevance | 2 years ago | Gretchen Schmauder | Hardware | |
| The cables between the sensors And the MFAM module are flexible circuit boards, And the length is limited to 20 inches. It is possible to remove the MFAM module from the Development kit box And then reconnect it using a ribbon cable. That would allow you to extend the MFAM module And sensors away from the Dev Kit box. Our engineers have tested it to 4 meters. Below are some details about the ribbon cable. The connector on the MFAM unit is Samtec FSH-110-04-F-DH. Its mating connector is Samtec SFMH-110-02-L-D-WT. The easiest option for an extender cable between the MFAM And the Dev Kit is a pair of cable assemblies from Samtec www.samtec.com which has male/female mass terminate connectors put onto a ribbon cable. These connectors plug directly into the MFAM I/O connector And also into the Development Kit. We are comfortable with lengths to 10 feet total. The samtec P/N for this cable is: FFMD-10-T-60.00-01-F-N The ‘60.00’ number specifies the cable length in inches (which equals 5 feet). We have found that there is generally a 2-4 week lead, time since they are made to order And not an off-the-shelf part. (There is another solution as well if you want to make adapter boards at each end (Dev Kit And MFAM). The exact Samtec mates for the MFAM / Dev Kit connectors are made in PCB mount connectors only, so if you make simple small adapter board to adapt the samtec connector to another connector of your choice. We've done this with ExpressPCB which is fast And inexpensive. A board set from ExpressPCB is about $70 including shipping. Our Engineering Team has a design And parts list they can send you if you're interested in going this route.) | |||||
| Differences Between our Standard Cesium Magnetometers and the SX Model | 1 Relevance | 2 years ago | Gretchen Schmauder | General Magnetometer Info | |
| 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. | |||||
| 1000 Hz Sample rate and Powerline Variations | 1 Relevance | 2 years ago | Gretchen Schmauder | Application | |
| The MFAM Magnetometer samples at 1000 Hz, which in turns captures a lot of unique waveforms. When viewing the data raw, it can therefore appear to be a bit noisy. But a closer examination of the data will reveal a real variation of the magnetic field which is caused caused by the power distribution network. Proper filtering is required to reduce the power line caused variations And reveal the strong signal of interest. It is not obvious that 60 or 50 hertz electromagnetic radiation is real, since in ordinary experience any power line “noise” is electrostatically coupled into a system (think 60 hertz hum on a stereo system) And is a fault that needs to be fixed. In this case however the variation in the magnetic field is induced by the power grid And is real. The magnetometer is simply And dutifully reporting the variation. These power line variations are to some extent present everywhere – even miles from the nearest power line. But obviously being close to power lines will increase the amplitude of the variations a lot. Often on a MagArrow survey the power line variations will be larger at one end of the survey area than the other. Poking in the GPS coordinates at the survey area nearest the larger variations into Google Earth will usually reveal the power lines from an aerial view – even if they are not visible on the ground. After applying a Fourier Frequency Transform on the MFAM data to identify the noise sources, 50 And 60 Hz noise amplitudes are easily observed. Also observable is the likely to be 20.8 Hz Schumann resonance of the third node And some other ultra-low frequency electro magnetic radiation produced naturally by the Earth. Harmonics of 60 Hz are also present. Another common question is “Why is the power line variations not a sine wave like the power line voltage?” Remember that voltages do not make magnetic fields. Only current generates magnetic fields, And the current being drawn is not a sine wave at all. Many loads, for example, only draw current at the voltage peaks. This makes for a non-sinusoidal magnetic field that is rich in harmonics. Also note that most power distribution system use a 3 phase topology. The ripple current in such a system will be 150 or 180 Hz. Thus you will often see large peaks in the power spectrum at these frequencies And their harmonics. | |||||
| 1000 Hz Sample Rate and Powerline Variations | 1 Relevance | 2 years ago | Gretchen Schmauder | MFAM | |
| The MFAM Magnetometer samples at 1000 Hz, which in turns captures a lot of unique waveforms. When viewing the data raw, it can therefore appear to be a bit noisy. But a closer examination of the data will reveal a real variation of the magnetic field which is caused caused by the power distribution network. Proper filtering is required to reduce the power line caused variations And reveal the strong signal of interest. It is not obvious that 60 or 50 hertz electromagnetic radiation is real, since in ordinary experience any power line “noise” is electrostatically coupled into a system (think 60 hertz hum on a stereo system) And is a fault that needs to be fixed. In this case however the variation in the magnetic field is induced by the power grid And is real. The magnetometer is simply And dutifully reporting the variation. These power line variations are to some extent present everywhere – even miles from the nearest power line. But obviously being close to power lines will increase the amplitude of the variations a lot. Often on a MagArrow survey the power line variations will be larger at one end of the survey area than the other. Poking in the GPS coordinates at the survey area nearest the larger variations into Google Earth will usually reveal the power lines from an aerial view – even if they are not visible on the ground. After applying a Fourier Frequency Transform on the MFAM data to identify the noise sources, 50 And 60 Hz noise amplitudes are easily observed. Also observable is the likely to be 20.8 Hz Schumann resonance of the third node And some other ultra-low frequency electro magnetic radiation produced naturally by the Earth. Harmonics of 60 Hz are also present. Another common question is “Why is the power line variations not a sine wave like the power line voltage?” Remember that voltages do not make magnetic fields. Only current generates magnetic fields, And the current being drawn is not a sine wave at all. Many loads, for example, only draw current at the voltage peaks. This makes for a non-sinusoidal magnetic field that is rich in harmonics. Also note that most power distribution system use a 3 phase topology. The ripple current in such a system will be 150 or 180 Hz. Thus you will often see large peaks in the power spectrum at these frequencies And their harmonics. | |||||
| Understanding Acquisition Filters in Seismographs - Their Use and how to Filter | 1 Relevance | 2 years ago | Gretchen Schmauder | Software | |
| Low Cut: , 10, 15, 25, 35, 50, 70, 100, 140, 200, 250, 280, 400 Notch: 50, 60, 150, 180 High Cut: 32, 64,125, 250, 500 or 1000 Hz The first recommendation for cases when you are having trouble getting sufficient signal to noise would be to increase your signal via stacking the data with multiple source events or get a more powerful seismic source. This will usually produce better results than the application of filters. Another approach would be acquire data when the noise sources are less present. That may mean collecting data at night when the area is closed or the traffic is less. Early morning can be better for areas where the wind tends to increase during the day. The selection of filters is very site dependent And can depend on a variety of factors as well as the type of survey being performed. 1) Typically the Notch filters are to remove noise due to electrical power lines (50 or 60 Hz And their harmonic frequencies depending on the country you are in). 2) Low cut filters are generally used for noise due to wind And moving vehicles, but care must be taken not to remove too much bandwidth from generated seismic signal. Often the noise sources have the same frequencies as the seismic data you are interested in And can’t be effectively removed using frequency filtering. 3) High cut filters can be used to remove noise from high frequency vibratory signals such as compressors or airplanes. In general it is best to record the data without any frequency filters And filter in post processing or only on the displayed data in our software. It will be a matter of experimentation to determine the best filters at your site. Modern 24-bit seismographs (Geode, Stratavisor, ES-3000, etc) have a much wider range of signal amplitudes that they can record accurately. This means that they can still accurately record smaller seismic signals even in the presence of larger noise signals. Therefore there is a reduced need for analog filters that are applied prior to digitization of the signals. Digital filters are more flexible And can be more specifically applied to the noise that is recorded rather than the “Broader Brush” of analog filters. Digital filters also have the benefit of being able to go back to the original data if the wrong filter is applied, which is not the case with Analog filters. The general approach in the seismic industry is now to record everything – including the noise – And the filter out what you don’t want later. | |||||
| Use and Care of G-857/G-858/G-859 Batteries | 1 Relevance | 2 years ago | Gretchen Schmauder | Hardware | |
| 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. | |||||
| Refraction and "other" modes explanation in SCS | 1 Relevance | 2 years ago | Randl Rivera | General Seismograph Info | |
| Question: Under the Geom>Survey Mode appears a window with "Refraction And Other." Before it was refraction And reflection. Now "other" means? Thanks for your help! Thank you for reaching out. The manuals And technical documentation on our website And our new forum are good resources for questions regarding your hardware And software. "When you are in Refraction Mode, the seismic software treats some of the data scaling operations differently. Autoscaling operations are done based on the amplitude of the noise before the first breaks to minimize the amount of manual scaling that may be necessary. In Reflection or Other Mode, trace autoscaling is done by normalizing each trace to the maximum value of the trace shown on the display. Note: These are display features only – they do not affect the actual data. Refraction data acquired while in reflection or other mode, And vice versa, are perfectly valid." | |||||
| RE: Geometrics preliminary MagArrow and MagEx data processing program download | 1 Relevance | 1 year ago | Ahmed Ramadan | Software | |
| Hello Dears, I'm new to Geometrics products And interested in MagArrow. I have some questions please. As a geophysicist, I examined the attached data And applied heading compensation to the measured data. My questions are after applying the 4th difference filter (the last panel in the attached figure) which is very important for measuring data noise especially comTing from the drone. I found the range to be very high And exceeding +/- 0.1, even after applying low pass filter to reduces the sampling rate of data from 20 Hz to 10 Hz. I think one of the biggest advantages of the MagArrow is that the sensor is suspended 3 meters below the drone to cancel out the effect of the noise coming from the drone, so I need to explain that. Attachment : 4th difference.jpg Secondly, in the attached file of the survey, the range of the total magnetic field data is about 43,000 nanoTesla, while when calculating the IGRF for that region based on longitude And latitude, I found that the range is about 49,000 nT, which is very far from the measured data? Could you please explain to me the answers to these questions because our goal is to explore minerals And not UXO. Kind Regards, Ahmed | |||||
| MFAM 1 PPS signal input, 10 MHz reference input and synchronization | 1 Relevance | 2 years ago | Rui Zhang | Hardware | |
| The 1PPS pulse phase locks And synchronizes the sample interval to be in lock step with the GPS. Thus once locked there will always be 1000 samples per second, with the sample beginning time precisely lined up with the 1 PPS edge. The 10 MHz input is for a different function. This input phase locks the 40 MHz master reference oscillator to the incoming 10 MHz, which is usually a GPS disciplined reference oscillator or atomic clock (in other words exactly 10 MHz). This phase locks the 40 MHz reference oscillator to exactly 40 MHz. The 40 MHz oscillator is the time base reference for calculating the Larmor frequency, And therefor the magnetic field value. Even though the 40MHz oscillator is really good even without the 10 MHz input, there is some drift in the 40 MHz over time (mostly thermal drift And some aging). For some applications where they need to measure very low frequency And low amplitude changes in the magnetic field the 10 MHz input will allow drifts in the reference oscillator to be removed. Without that it would be impossible to distinguish between reference oscillator drifts And low frequency low amplitude changes in the magnetic field. The connector for the 10 MHz input is SMB RF connector from Molex. If you must simulate the 1 PPS signal in a GPS denied environment, please be aware of certain requirements of the 1 PPS signal. 1. The lock range for the 1 PPS input pulse is very narrow. The simulated 1 PPS signal must be within 100 ppm of an exact 1 Hz PPS signal (100us). 2. Timing jitter must be small (less than 0.5 ppm, 0.5us) too. If you are setting a GPIO pin on a microcontroller, there may be some concern about timing jitter due to interrupt latency or other processor tasks delaying the I/O pin toggle. Any rectangular waveform should work but the leading edge must be very close to 1 Hertz. It is the positive edge that specifies the 1 second rollover. | |||||
| Understand Dead-zone, Heading Error, and their importance for the MagArrow | 1 Relevance | 2 years ago | Gretchen Schmauder | Application | |
| Dead-Zones The MagArrow is a dual sensor magnetometer powered by MFAM sensors, but it is configured for use so it only has a single data output. The reason Geometrics has done this is so we could ensure the MagArrow encounters no "dead-zones". A dead-zone occurs when the orientation of a magnetometer results in the magnetometer producing poor or no measurements. The dead-zone angle depends on the location of survey. Since we have the two MagArrow MFAM sensors in orthogonal orientations, the MagArrow Magnetometer has operability worldwide without affecting survey orientation, making it much easier to use for the customer. Heading Errors Heading errors are a type of noise magnetometers can experience. They come from three sources: Sensor Console Operator Magnetic materials in the sensor itself are the primary cause of heading errors. The physics of Cesium And Potassium magnetometers can contribute small amounts to the total heading error. Magnetic contamination near the sensors, operating electronics, or operator can all contribute to heading error. Heading errors look like herringbone patterns in survey images. Alternate lines can also be corrugated. Dead-Zones vs Heading Errors while these two sources of error in magnetic data are different, there is overlap between them when operating a magnetometer like the MagArrow. Heading errors can be fixed relatively easily in software, where dead zones can be much harder to manage. If a line is completely ruined because of a dead zone then they will need to re-fly the line/mission which is time consuming. Even with advanced users, these sorts of mishaps can happen. Additionally, the closer a mag sensor operates to a dead-zone, the larger a heading error will be measured. With compensation software And a pre-survey heading error flight, heading error can be reduced dramatically to around 1 nT for the MagArrow. Click to view the difference between Raw And Processed MagArrow Data The MagArrow is only outputting a single value as a means to create a “no-dead-zone” system. Obviously each sensor has a dead zone themselves, but with the sensors orientated orthogonally at least one sensor at all times will have a magnetic measurement. By combining the measurements from both sensors it is possible to generate a constant magnetic field measurement independent of orientation And location in the world. If the data from each MFAM sensor in the MagArrow was individually reported there would be gaps in the mag fields observed by either sensor as you fly, rotate, And swing. | |||||
| How fast do seismic waves travel and what controls this? | 1 Relevance | 2 years ago | Gretchen Schmauder | General Seismograph Info | |
| Different types of seismic waves travel at different velocities through any given material. In addition, different materials have different seismic properties, meaning that any one wave type can have a wide range of velocities, depending on the material properties. For instance, the p-wave velocity of shale can range from 800-3,700 m/s. Granite can range from 4,800-6,700 m/s. Because of this, by themselves, seismic velocities alone are not particularly diagnostic with regard to rock type. Ultimately, seismic velocity depends on the density And elastic properties of the material, whatever its composition. Specifically, Compressional-wave velocity depends on the “incompressibility” of the material, as embodied in the bulk modulus. The higher the bulk modulus, the less compressible the material, And the higher the p-wave velocity. Sound travels through water about four times faster than it does through air. Similarly, shear-wave velocity depends on the rigidity of the material, or the resistance to shear. The higher the shear modulus, the higher the s-wave velocity. Mathematically, where K = bulk modulus µ = shear modulus ρ = density Note that Vp depends on both the bulk And shear modulus, while Vs depends only on the shear modulus. This observation implies two things: Shear waves always travel slower than compressional waves through a given material. Materials with zero rigidity – i.e., fluids – do not carry shear waves at all. Therefore, the absence or presence of groundwater has no effect on the shear wave velocity. It is interesting to note that, in general, seismic velocity increases with density – denser rocks tend to be much harder And faster. Yet in the above equations, density is in the denominator. This is known as the “velocity-density paradox”, the answer to which can be found in the fact that the elastic moduli tend to increase with density as well, And at a faster rate. | |||||
| RE: Geometrics preliminary MagArrow and MagEx data processing program download | 1 Relevance | 5 months ago | Andre Yudhistika | Software | |
| hi, i have downloaded the .exe file. when i ran it, it showed 'trial expired' do you have new version available or new trial? thank you | |||||
| Geometrics preliminary MagArrow and MagEx data processing program download | 1 Relevance | 2 years ago | Rui Zhang | Software | |
| The zipped files can be downloaded here: Attachment : Survey_Data_Processing.zip After unzip, please keep all files And folders! Before you run the program, please download And install the LabView Runtime (free, 64-bit 2020 SP1) first: The user guide is located in the folder. It is worth mentioning that the data processing program provides 2 methods of suppressing the survey noise: 1. Through frequency filtering And line levelling (Survey Data Noise Reduction).2. Heading effect compensation (Heading Error Compensation). In general, to perform the heading error compensation, you need to collect heading effect calibration data (Instruction included in the folder). It is possible that the calibration data can be obtained from the survey data itself. If you have trouble processing your data, please share some of your data with Geometrics And we can provide help, especially in generating the calibration file. If the trial version expires, please replace the configuration file inside the Config Files folder with the new one below: Attachment : HE Configuration File.zip Leave a comment if you have questions! | |||||
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