Comparing the PEV Servo and Tau 2 Fast Forward Polarization Controller Modes
Build a Geomagnetic Observatory ! 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, Links and References (very early stages)
Journal Notes:
Monday, May 9, 2011
Overnight: PDF, TXT. The geomagnetic field was quiet overnight. A surprising number of measurements have had a figure of merit (FOM) in the e-9 range this run (since pm 5/7) PDF. Our present operational settings are: preset desired peak envelope voltage (set point) 0.85 V; USB 6008 input range +/- 1V; polarization current current 1.5 Amps; polarization time - programatically controlled, dynamically varied measurement to measurement to achieve the desired peak envelope value. Presently running in the Tau 2 feed forward polarization time controller mode. In the Tau 2 feed forward polarization time controller mode, the polarization time for the next measurement is calculated from a moving average of past measured Tau 2 values. An equation is used to open loop calculate the polarization time needed for the next measurement cycle. The equation was derived by curve fitting data from the closed loop PEV servo mode.
Tuesday, May 10, 2011
Overnight: PDF, TXT. There was a significant fast rise in the geomagnetic field this afternoon, albeit so far, at sub-storm levels (K4) PDF. The small step change at about 4 pm local (UTC -4) was vehicle related.
Wednesday, May 11, 2011
With about 1197 plotted points on the present run in the Tau 2 feedforward polarization time controller mode, polarization time controller chart PDF, figure of merit (FOM) and FDM amplitude PDF, Tau 2 - polarization time PDF. The FOM statistical mode (most common value is) 1e-7. The slight varation in the peak envelope voltage and FDM amplitude over time show errors (minor) related to the present working Tau 2 - polarization time equation.
For new readers, we dynamically control the amplitude of the proton precession signal by varying the polarization time (the width of the polarization pulse). We "learn" (using post processing manual methods) the relationship between polarization time and Tau 2 (related to the fall time of the precession waveform) with temperature using a closed loop. The closed loop "PEV servo" mode automatically sets the polarization time to maintain a desired peak amplitude voltage. Then, using an exponential equation derived from data taken in the closed loop mode, we can operate open loop in the "Tau 2 feed forward mode". In the Tau 2 feed forward mode for a moving average of recent measured Tau 2 values, we can calculate the next polarization time value to use for the each next measurement. The run data described above was taken in the Tau 2 feed forward polarization controller mode.
Afternoon, we had to shut down for a Windows update and re-boot. On this new run, we will go a day or two in the PEV servo mode (a closed loop polarization time controller mode) for a short term comparison to the Tau 2 feed forward mode.
Thursday, May 12, 2011
Friday, May 13, 2011
Back in the PEV servo polarization time controller mode since the afternoon of 5/11. Polarization time controller chart PDF, FDM FOM and amplitude chart (statistical mode 2e-7) PDF, Tau 2 - polarization time graph PDF.
Saturday, May 14, 2011
Sunday, May 15, 2011 - K4!
Overnight: PDF, TXT. The geomagnetic field is unsettled today here in upstate, NY, US (a number of the small step offsets are vehicle related) PDF. The NOAA Wing Kp model is forcasting more activity PDF. Afternoon: an active geomagnetic day, as predicted PDF. Late evening PDF.
Project Documentation, Links and References (very early stages)
QUESTIONS/COMMENTS/notice of typos, etc. send email to joegeller @ gellerlabs dot com
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