Journal notes, More user accessable controls
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.
Project Documentation, Links and References (very early stages)
Journal Notes:
Monday, January 10, 2011
Tuesday, January 11, 2011
Overnight: PDF, TXT Brief thoughts on noise suppression and Field homogeneity: HTML.
Beta Tester Carl Olsen prepared a detailed SWCTRL assembly note, which can now be found on our Docs page under SWCTRL. Again, many thanks!
The description of the system grounding scheme has been updated, especially to emphasize certain ground breaks. There is a link on the Docs page. (Note that the grounding scheme has changed since our early FET-Relay hybrid circuit notes.)
Wednesday, January 12, 2011
Thursday, January 13, 2011
Overnight: PDF
Friday, January 14, 2011
Overnight: PDF, TXT There was an interesting program this afternoon on terrestrial magnetism on NPR Science Friday.
An easy way to search our site using GoogleTM, is to use the search phrase: www.gellerlabs.com: topic of interest or key words Note that our URL is part of the search string and after the colon and a space, enter a word or phrase as if you are using an electronic index.
Evening: FID amplitude with 100 point moving average since about 6:30 pm 1/11/2011 PDF. Outdoor air temp is below 5 F (-15 C), good thing we are running on 4 Oz (125 ml) of Prestone De-Icer windshield washer fluid (good to -30F). Occasional temps of -15 F (-26 C) are not uncommon here with a record low of -28 F (-33 C) for January and Februrary. The slight positive discontinuous offset after 1001 is curious.
Saturday, January 15, 2011
Overnight: PDF, TXT . More on the longer term (many points) minor amplitude variations HTML.
With each of our recent minor improvements, I have been reducing the gain the of the narrow band low noise ampifier (NBLNA). In looking to lower the NBLNA gain again, I noticed that we are already operating at the lowest available gain. So, the value of R15 was reduced to 2.2 k (from 4.99 k) and the R12 trimmer reduced to 10 k (from 20 k). The gain was set for a precession envelope peak of about 1.6 V peak. The precession waveform display can now be seen to be just topping out between about 1.8 V and 2 V for this gain setting. In recent days, our % success has been running about 82% to 85%. It will be interesting to see if there are any changes for a slightly lower NBLNA gain. Evening, as of this evening, at 190 plotted points the success rate has been about 81 % or 82%, another surprisingly consistant number that needs further study. When the percent success rate becomes dominated by failed measurements due to, for example, moving vehicles, I would expect more variation, another parameter unimportant to normal operation for the intended use, but curious at that.
Sunday, January 16, 2011
As beta testers approach operation, we changed many parameters over to user settable variables. The multiplier (scale factor) allows users to "calibrate" a FDM magnetometer for their own USB 6008 digitizer. The Exp FV (final value) variable allows users to experiment with the exponontial window (apodization), or more importantly, to set the variable to 1, effectively turning the windowing function off to observe the"raw" digitized signal. With the polarization power supply turned off, the raw waveform can be used to study ambient noise levels in the time domain. The time line variables have also been "exposed", however caution is advised with regard to the delay times and the defaults should be used during initial operation. The polarize time can be varied at will, for example, for experiments in exploring the tau 1 of various fluids.
Here is an example of a 3 second digitization window following a 5 second polarization cycle with no windowing PDF.
Here is an example of the standard 1.1 second window with the polarization supply off and no windowing PDF.
While some parameters can be set dynamically, for now to have correct graphical displays, basic parameters, such as number of samples and sample frequency are set before the start button (arrow) at the top left of the page is pressed. To change these basic parameters, press the stop button at the top of the page, set the new desired values, then press the start arrow again.
Example of the latest LabView version in operation PDF.
Local Network only Live copy.
Added the FDM figure of merit (FOM) in nT (FOM x F field), and Normal and Fast cycle timing as user controls:
Project Documentation, Links and References (very early stages)
QUESTIONS/COMMENTS/notice of typos, etc. send email to joegeller at gellerlabs dot com
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