Journal notes, Characterizing the Analog Board
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)
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 (very early stages)
Journal Notes:
Monday, July 26, 2010
Overnight: PDF, TXT, several day view PDF.
I came across a very interesting PhD thesis a few days back (using GoogleTM of course). The thesis is directed largely towards Earth's field NMR spectroscopy, however there is much useful information regarding EFNMR in general. Long time readers might remember that we briefly discussed EFNMR spectroscopy some months back (see: January 24) in reference to Appelt's 2006 paper. This Thesis, MULTI-ACQUISITION AND MULTI-DIMENSIONAL EARTH'S FIELD NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY by ME Halse is a remarkably readable treatise that includes the history and basic physics underlying EFNMR. More advanced experimenters will probably find her initial derivations of the Larmor relationship extremely interesting. For less mathematical readers, if you scan through her work with some patience, you will be rewarded by many very clear explanations of basic NMR and EFNMR terms and principles in plain English. I am only up to page 44 as of this evening, and enjoying the read very much. I feel as though I was just given a gift of a brand new $200 text book!
Tuesday, July 27, 2010
Overnight: PDF, TXT, NRCan OTT PDF, several day view PDF.
We completed Part I of our planned series of articles, an Introduction to the Backyard Magnetic Observatory Project. In this introductory article, the vector components of the Earth's field are introduced, we briefly discuss the use of fluxgate and proton magnetometers, and we list online references for the amateur space weather observer. Part I was written at a technical level that we hope will make the article accessible to the widest possible audience. Many thanks to those who took the time to review the article for technical accuracy and typos! The PDF is available at the Project Articles page.
A little activity tonight, PDF, notice that the overnight period, especially the late evening approaching 12 AM, is generally a relatively quiet time in the geomagnetic field, several day view PDF. The total field excursion here in upstate NY is not all that dramatic, although the overall disturbance has been classified as a G1 minor geomagnetic storm (K5), NOAA Space Weather Now PDF, NOAA K PDF. Later (2am), all is relatively quiet PDF again.
Wednesday, July 28, 2010
Overnight: PDF, TXT, NRCan OTT PDF, It continues to be of interest how our plots so closely follow the NRCan OTT station F magnetograms in recent weeks and months, and less so, the FRD plots from Virginia that we initially used as reference plots. Perhaps there are some seasonal factors related to location and distance and direction from the nearest observatories.
I revisited the analog amplifier noise measurement this morning. Using techniques learned from our JCan experiment, I tested the amplifier with a short and three input resistances. The two 10 kilo ohm biasing resistors were treated as a parallel R of 20 kohms. The output AC voltage was measured with an Agilent 34410A DMM using the statistics display TXT, PDF. (just the JCan technique and spread sheet were used, not the JCan hardware)
Using a gain of 474,000, an effective noise bandwidth of 168 Hz, and a shorted-input output AC voltage of 10.3 mV, the new computed input referred noise for the assembled prototype analog PCB is 1.7 nV/rt Hz. For this measurement, we assumed the previously measured gain of 474,000 and slewed the effective noise bandwidth to 168 Hz to match the theoretical Johnson noise curve. While these measurements can be further reconciled, it is unlikely that the 1.7 nV/rt Hz number would move much more.
Afternote: While the handwired prototype was correctly wired, there was an error on the protoype NBLNA PCB. The new numbers are: Gain: 588,000, effNBW: 181 Hz, noise floor: 1.8 nV/rt Hz. See our August 31 journal entry.
Also, I cleaned up the stand and put another coat of polyurethane on it this afteroon. As discussed earlier, the stand was made using 2"x2" pressure treated wood and oak dowels. The extensions beyond the plastic container (which holds the sensor counter-wound coils) were cut off to allow for a smaller plastic bag rain cover. JPG1, JPG2.
Thursday, July 29, 2010
Overnight: PDF, TXT. Ramps, such as the one between about 8 am and 10 am provide a great opportunity for backyard calibration and verification of other types of magnetic instrumentation.
Friday, July 30, 2010
Last day and a half: PDF, TXT.
Saturday, July 31, 2010
Sunday, August 1, 2010
Project Documentation (very early stages)
QUESTIONS/COMMENTS/notice of typos, etc. send email to joegeller at gellerlabs dot com
COPYRIGHT © 2009, 2010 JOSEPH M. GELLER, All rights reserved.