Journal notes, More comparing to OTT plots, analog printed circuit board (PCB)
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 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)
Sunday, July 4, 2010
Overnight: PDF, TXT, NRCan OTT PDF.
Monnday, July 5 , 2010
Overnight: PDF TXT, NRCan OTT PDF.
Tuesday, July 6 , 2010
Overnight: PDF, TXT, NRCan OTT PDF.
We have been designing the amplifier printed circuit board, since the July 4th weekend.
Wednesday, July 7 , 2010
Down for a short while, took apart the amplifier to compare it to the prototype PCB design.
Friday, July 9, 2010
Overnight: PDF, TXT, NRCan OTT PDF.
Completing, revising, and checking the amplifier PC board layout (still working at 5am!), first prototypes anticipated in about 2 weeks.
Afternoon: Ordered first prototype PC boards (V 0.8) from from Advanced Circuits using their prototype special!
After working with several excellent professional draftsman for PCBs for my various projects over the years, I finally put in the effort into to learn a PCB CAD program. We chose to try out Cadsoft's Eagle PCB. Although still on the learning curve, I was able to design exactly the layout I wanted. I am very impressed by Eagle. I worked on this first analog board on and off for more than a week (far more hours than I care to admit). It is such a pleasure to be able to do my own editing. While the pros work a lot faster, I can now make as many changes as I need without incuring extra cost or the wrath of a designer frustrated by my many changes.
It is so difficult to decide when a board design is close enough to go for the first prototypes. I thought I was ready to go, then by some small miracle, we delayed by a day (becuase of a quote that never got here) and I saw many more small changes. I think the analog board is nearly finished now. There have been no stability or oscillation problems with the handwired prototype board, however, these ultra high gain analog boards can be tempermental. I spent a lot of time physically locating components and stages and adding guard traces to make for a stable design. I am hopeful this first layout will workout okay, time will tell.
Saturday, July 10 , 2010
Last couple of days at 5 nT / div (The field has been relatively quiet, reduce to 10 or 20 nT / div to compare to other observatory reported graphs) PDF, TXT. A total span of less than 50 nT is typical for our local diurnal variation.
For most experimenters who eventually build our FDM proton precession magnetometer kit, FDM will just be a name of a software routine within our code. However, for very advanced experimenters and university students, see Jianhan Chen's webpage on the Filter Diagonalization Method for a clear and concise description of FDM. As discussed in earlier posts, the exceptional resolution and accuracy of our magnetic field measurements are directly attributable to Professor Mandelshtam's original FDM code, on which this project is based. I would like to think it also took some good electronics design, however use of FDM in place of more conventional frequency estimators such as zero-crossing techniques, FT (FFT, Buneman type estimators), and phase-slip methods, is truly what distinguishes this design from past proton precession magnetometer designs.
Project Documentation (very early stages)
QUESTIONS/COMMENTS/notice of typos, etc. send email to joegeller @ gellerlabs dot com
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