Journal notes, minor G1 magnetic storm, more testing
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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Project Documentation (very early stages)
Journal Notes:
Monday, October 4 , 2010
Overnight: PDF (10nT/div), TXT. Quiet, same period ten times vertical magnification, 1 nT/div magnetogram PDF.
Sample spectra PDF, log spectra PDF.
Tuesday, October 5 , 2010
Very early morning (~3am): Interesting disturbance, sine or triangle wave shaped between about 1 am and 2 am (5 to 6 UTC), albeit relatively minor at about 8 nT peak to peak PDF, TXT, USGS PDF, NRCan OTT PDF. Expanded view of our magnetogram PDF. Most interesting is that the peak amplitude appears to have occured at the mid latitudes. The Costello index is unfortunately down this morning, there are no alerts or warnings at NOAA space weather, so it appears to be just a minor disturbance, perhaps only noteworthy in that it follows so many days of extreme quiet overnight. It was a little stronger in Japan (20 nT), PDF, possibly due to how the Earth was facing the solar wind when the disturbance happened? Same event on the GOES 11 and 13 satellite magnetometers PDF. Just interesting, this is believed to be a very minor, perhaps insignificant event.
This sort of event raises the question again of whether there should be an automatic sample rate increase during interesting events?
Overnight: PDF, TXT. There was another comparable event at about 4 am (8 UTC) (our magnetogram, expanded scale) PDF, NRCan OTT PDF, USGS PDF, this time the amplitude was somewhat lower here in upstate, NY.
Wednesday, October 6 , 2010
Overnight: PDF, TXT, relatively quiet overnight.
Saturday, October 9 , 2010
Taking some time to put the project in perspective and to continue testing while pausing before ordering the next round of prototype printed circuit boards.
In one test, the hp 3581C frequency selective voltmeter was setup again, this time with a hp 54645A digital scope to record the envelope of the precession waveform. The 54645A has an autostore mode comparable to old analog storage scopes, more commonly called analog persistence today. Here is a screen print of several hours of envelopes (the digital data is only representative of the most recent measurement) PDF. There are two very interesting aspects of the newest prototype. First, in the early prototypes, there were often "runt" cycles of ocassional low amplitude or very distorted envelopes. Those distorted envelopes are virtually non-existant now. Another curious feature is the small pulse at the beginning of the leading edge. With all of the RC and RCL time constants involved in switching the coils into the center-tapped counter-wound configuration and coupling to the input of the narrow band low noise amplifier, it is not surprising at all that there might be some transient behaviour. The curious part, however, is that there are many envelopes without the early pulse or with exactly the same duration, but of greatly varying amplitude of the small entry pulse. It is virtually a non-issue for operation, just curious at this point. The trigger was one of the digital control signals from the USB6008.
The hp 54645A is a surprisingly handy little scope (we picked it up at modest cost as a repair effort that really paid off). Since it has a deep memory, the calculated parameters (e.g. envelope fall time) are easily resolved to 4 digits. Previous measurements with an older hp 54503, even with its great trigger performance, were marginal because there were way too few points per single shot sweep for these sorts of envelope measurements.
In other testing, we are studying contact bounce and high repetition performance for several small signal relays using a LeCroy LT344L scope and LeCroy's Scope Explorer software to make PDFs. One of them is presently running well at 100 Hz for destructive accelerated life testing. This repetition rate is well beyond its ratings, however after an hour is still running fine PDF. The top trace 3 shows the coil operation, low is energized, high is off (no coil current). In trace 1, the 200 uS wide green vertical bar shows the bounce as the normally closed contacts close (NC contacts are closed with no coil current, relay off) (testing with ~1 mA, recall we only switch at zero-current). Trace 2 at the bottom shows the normally open contacts opening after the relay is de-engerized. Here color analog persistance shows variation measurement to measurement. These measurements are updating slower than 100 Hz. Our actual relay operation rate is presently once per 2 minutes, with occasional auto-retry operations (one to n) at about one auto-retry per 8 or 9 seconds. If the average is once per minute, we anticipate 60 operations per hour compared to 360,000 operations per hour at 100 Hz. So, our accelerated life testing is about 6,000 times (sped up) over normal time, or equivalent to 6,000 hours of normal operation, every hour!
Sunday, October 10 , 2010
Overnight: PDF, TXT, all quiet.
Monday, October 11, 2010 - G1 Minor Magnetic Storm
Overnight: PDF After weeks of quiet, there is a minor Geomagnetic Storm in progress this morning, expanded scale PDF, a relatively minor storm here in upstate, NY.
Early afternoon: PDF, TXT, NRCan OTT PDF, USGS PDF, NOAA Space Weather Now PDF, Costello prediction index PDF.
Early evening: The storm is over, yet the geomagnetic field continued to be active through the afternoon (albeit a minor storm). Unfortunately the vehicle parked closest to the sensor (~33 feet) went out for a while, however the offset can be seen very clearly, so you can mentally shift that part of the magnetogram back down to where it should have been. PDF, NRCan OTT PDF.
Late night/early morning: The geomagnetic field is somewhat active: PDF.
Tuesday, October 12, 2010
Overnight: PDF, TXT. There was swing of almost 18 nT before 3 am which might have been part of the continued recovery from yesterday's minor event. The early morning hours were slightly active over past quiet days. NOAA K indexes for yesterday's minor storm: PDF.
Project Documentation (very early stages)
QUESTIONS/COMMENTS/notice of typos, etc. send email to joegeller at gellerlabs dot com
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