Journal notes, BETA Kit!
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
(be sure to hit refresh to pick up our latest changes and entries)
Project Documentation (very early stages)
Journal Notes:
Monday, December 6, 2010
Overnight: PDF, TXT. The spikes are the usual garbage trucks, school buses, and now with the onset of winter, snow plows (they often pause and turn at a nearby corner, sometimes several times). The snow came late to our area this year, and so far only a few inches at a time, well under our normal for this time of year.
Tuesday, December 7, 2010
NBLNA Parts List: I added a parts list for the FDM proton precession magnetometer narrow band low noise amplifier (NBLNA) module on the project documentation page (lower down under PCBs and schematics).
Wednesday, December 8, 2010
Overnight: PDF, TXT. There is a slight increase in activity as indicated by the NOAA Costello Index PDF, only significant in comparison with the quiet magnetograms of recent days and weeks.
SWCTRL Parts List: I added a parts list for the FDM proton precession magnetometer switch control (SWCTRL) module on the project documentation page (lower down under PCBs and schematics) If you have visited the docs page before, remember to do a refresh on your browser (typically the F5 key on a PC browser) to see the latest version.Please do not hesitate to tell us if you are following the project and notice errors.
Thursday, December 9, 2010 First Beta kit!
Overnight: PDF, TXT. Improved the organization of the Project Docs page. Packing a BETA kit! JPG It takes a LOT of time to pack a FDM magnetometer kit! The kit includes all parts to build the NBLNA and SWCTRL modules. The kit does not include power supplies or the NI USB-6008 module (experimenters do not need lab supplies, many relatively simple power supplies, including home brew power supplies will work fine), the USB-6008 module is available from National Instruments (under $200, and there are academic discounts from NI). The kit also does not include the counter-wound coil pair, PVC parts, cable to the outdoor sensor (four wires, shielded two twisted pair is best, other four wire cables will probably work okay), or the wood sensor stand.
I corrected an error on the SWCTRL parts list. The resonating capacitor bank is set to resonate with the inductance of the series combination of the center-tapped counter-wound coil pair for your local nominal total F field (the nominal Larmor frequency, f (Hz)=field nT/~23.49446). There is some mutual inductance between the two coils, so you can do a first cut estimate using the NOAA field calculator (allows geographic entry by lat. lon. or by country and city, or zip code) and an RLC calculator f=1/(2pi Sqrt (LC)), then fine tune by trial and error for the maximum signal strength (e.g. as observed on the precession waveform filtered envelope display graph).
Friday, December 10, 2010
Overnight: PDF, TXT, several day view PDF. It is interesting to see that our average field value has fallen to about 53730 nT now. The large positive offsets were caused by one of our vehicles (normally parked within about 33 feet (10 meters) of our counter-wound coil sensor pair) going out (a +18 nT offset which is otherwise accounted for in our reported field values). The increased number of spikes is not noise, but snow plows running on two adjoining roads and stopped to navigate a tight corner.
Saturday, December 11, 2010 First Draft: PART IV Article on the sensor stand and coils
Overnight: PDF, TXT another relatively quiet magnetogram. Several day view, PDF (5 nT/div).
I added a first rough draft of the Part IV article on building the sensor stand and winding the counter-wound coil pair sensor to our Project Articles page. I also corrected the frequency and field information in the Part II discussion of the Wadsworth article. It should have read: "Wadsworth reported his nominal precession frequency was about 2,025 cycles, which corresponds by the Larmor constant to about 47,576 nT. He reported being able to detect a change of about 2x10^-4 Oersteds (20 nT). A 1 Hz change to 2,026 Hz corresponds by Larmor to about 47,600 nT or a delta of 23 nT, so ~20 nT sounds about right." (Please feel free to tell us if you notice typos or mistakes.)
Sunday, December 12, 2010
Overnight: PDF, TXT, several day view PDF. Evening, some increased activity after 1500 UTC 12/12, particularly after 8:00 pm est (0100 UTC, 12/13) PDF, expanded vertical (1 nT/div) and time scales PDF.
Project Documentation (very early stages)
QUESTIONS/COMMENTS/notice of typos, etc. send email to joegeller at gellerlabs dot com
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