Build a Geomagnetic Observatory ! GELLER Labs "Backyard Science"
Thoughts on a proton precession magnetometer design - a Proton Magnetometer Project. Build an Earth's field magnetometer.
The FDM MAGNETOMETER1 project is a low cost high performance proton magnetometer (a digital magnetometer) kit under development for universities and amateur scientists to be able to accurately measure and monitor changes in the Earth's total magnetic F field and to observe geomagnetic storms. Magnetic storms can cause large excursions in the field and are of concern to interests ranging from electrical power grids, radio communications, and satellite operations, to aurora watchers and amateur radio operators.
1 Filter Diagonalization Method "FDM" (harmonic inversion), see Jan 21 and Jan 23 entries, based on: Vladimir A. Mandelshtam, Howard S. Taylor, Harmonic inversion of time signals and its applications, Journal of Chemical Physics (1997), Volume 107, Issue 17, 1997, Pages 6756-6769
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I created a new Proton Magnetometer Group at Yahoo groups for those interested in discussing proton magnetometers with an emphasis on Earth's field measurements. I will try to keep it as open as possible without getting attacked by spam. I will also try first with no review of posts, let's see what happens. Please keep it friendly and professional. Use of real names is preferred, possibly required in the future.
September, 2009
Well, it seems every couple to few years I start thinking about the famous C. L. Stong Scientific American Magazine, "The Amateur Scientist" column on Nicholas Wadsworth's proton magnetometer (more to follow on the Wadsworth article). Every time I go back and re-read the project, I marvel over how competent the description is and what a challenging design it must have been back then. Here is a low resolution snap-shot view of page 1 solely for purposes of identification. (We have not been able to obtain copyright re-print rights. Scientific American told us that they do not hold the copyright re-reprint rights for the column, and the presumed present owner of these rights, the last editor of the column, has not answered our several email inquiries.) The full article can still be found for free, or perhaps for the cost of copies, in many public libraries or private collections. Also, the February, 1968 Scientific American issue occassionally shows up on eBay.
I mention the Wadsworth/Stong article since so many of us over the years have attempted to build a single bottle absolute proton precession magnetometer (including non-gradiometer, noise cancelling double bottle versions) over the years based on, or at least inspired by Wadsworth's original project from that Amateur Scientist column. As discussed in our Part II article, while brilliant in its "simplicity" of design and inspiration, in hindsight, as gradiometers go, the Wadsworth instrument was actually pretty crude as to resolution (on the order of 20 nT). That said, the Wadsworth article, now from so many years past, was for sure the source of inspiration for our current project. Also, I hasten to add that by simplicity, I am referring to Wadsworth's overall technology. Anyone who has tried to assemble a gradiometer according to Wadsworth's plans will tell you, it was anything but simple to build a working unit!
NOAA's Space Weather Prediction Center posts a webpage on Solar Cycle Progression. During this lull in solar activity before the solar cycle maximum, GELLER (Geller Labs) is working towards a low-cost proton magnetometer kit. The goal of our project is a relatively low cost / relatively easy to build / high performance proton precession magnetometer suitable for home and school magnetic observatories. We plan to offer a box of parts including one or more printed circuit boards, most or all active and passive components, executable program code (currently Windows only, possibly a LINUX version in the future), and plans to build a stand and pick up coils (the sensor assembly). We are using National Instruments USB 6008 DAQ module for digital control and data acquisition. Kit builders will buy the USB 6008 DAQ module directly from the National Instruments (NI offers an academic discount for most colleges and university groups). Users will provide a PC or laptop, which does not need to be dedicated to the magnetometer application.
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May 7-22, 2013 Road construction near the sensor, offline or very disrupted readings for some days ...
LIVE VIEW - UPSTATE, NY (UTICA AREA) EARTH'S FIELD MAGNETOMETER:
experiments in real-time images (updates every 1 minute, click refresh)
Unfortunately, our daytime magnetograms often include numerous arrived and departed parked vehicles as indicated by small step changes. Also, during snow plowing, the plow truck does some slow maneuvering at a nearby corner. On Fridays, there are often cars closer to the sensor (on street parking for Friday night get togethers in the neighborhood), ah well, they provide another peformance check. We only hope there is never a major geomagnetic event on a Friday night!
Journal Notes:
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Wednesday, May 1, 2013
Overnight: PDF, TXT. There was about a 70 nT negative excursion in the total field early this morning about 4 am NY EDST time.
Thursday, May 2, 2013
Overnight: PDF, TXT. There was about a 80 nT positive excursion in the total field yesterday afternoon (some offsets from work trucks near the sensor).
Tuesday, May 7, 2013
Some time back we were wondering if the narrow band low noise amplifier (NBLNA) total harmonic distortion (THD) was changing as a function of gain settings. Steve Faber had suggest back then that what were probably seeing was the background noise levels changing with gain. Interestingly, by reducing gain and allowing the amplitude servo to increase the polarization time, we increase the signal to noise ratio. The increased S/N is because at lower NBLNA gain, there is less amplification of the undesired inband signal which is not related to the precssion signal (e.g. EMI/RFI pickup). Tonight, I finally had some time to look at THD as a function of NBLNA gain. Steve was correct, there is very little change in THD as a function of NBLNA gain, at least over the range we checked this evening. Notes on NBLNA THD testing.
Saturday, May 18, 2013 G1 Minor Storm
Want to build your own FDM Proton Precession Magnetometer?
For those visiting from the EDN article (welcome!) here is the full NASA/ESA caption for the SOHO illustration (too long for the magazine article): figure 1 SOHO (ESA & NASA) illustration caption : "CME blast and subsequent impact at Earth" "This illustration shows a CME blasting off the Sun’s surface in the direction of Earth. [The] left portion is composed of an EIT 304 image superimposed on a LASCO C2 coronagraph. Two to four days later, the CME cloud is shown striking and beginning to be mostly deflected around the Earth’s magnetosphere. The blue paths emanating from the Earth’s poles represent some of its magnetic field lines. The magnetic cloud of plasma can extend to 30 million miles wide by the time it reaches earth. These storms, which occur frequently, can disrupt communications and navigational equipment, damage satellites, and even cause blackouts. (Objects in the illustration are not drawn to scale.)": JPG Courtesy of SOHO consortium. SOHO is a project of international cooperation between ESA and NASA.
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QUESTIONS/COMMENTS/notice of typos, etc. send email to joegeller @ gellerlabs dot com
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