GELLER Labs "Backyard Science"
Thoughts on a proton precession magnetometer design - a Proton Magnetometer Project. Build an Earth's field magnetometer.
The goal of this project is a low cost high performance proton magnetometer (a digital magnetometer) kit 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. There is a regular daily (diurnal) variation in the Earth's magnetic field. During events related to solar activity, there can be sudden changes in the field (such as a sudden impulse) as well as large excursions in the field which can be more than ten times the regular diurnal variation caused by magnetic storms.
(be sure to hit refresh to pick up our latest changes and entries)
(some materials / code not available until publication of the project article)
FDM Proton Precession Block Diagram
A block diagram discussion of the project FDM Proton Magnetometer PART III Article
Block Diagram: PDF
Prototype Pictures
Working FDM magnetometer prototype: JPG All three power supplies from an eBay $50 surplus supply! (The battery in the background is for a prototype of an optional air temperature sensor) JPG, JPG, JPG, JPG (using an external polarization supply for slightly more current) older version: JPG1, JPG2
Coils: counter-wound coil pair JPG1 JPG2 JPG3 JPG4, older coils, JPG1 JPG2 Discussed May 19, 2010
Very Important => FDM Magnetometer electronics System Grounding.
COILS and Coil STAND JPG JPG JPG
Building a Sensor Stand and Winding the Sensor Coils PART IV Article , See also Jan. 26, Jan. 27 journal notes.
Use this new bobbin design: JPG January 25, 26, new 2.5" counter-wound coil pair JPG1 JPG2 JPG3 JPG4
Detailed Coil Stand Assembly Instructions contributed by Carl Olsen PDF
Detailed Coil winding Instructions contributed by Carl Olsen PDF
Another example of a well built coil stand by Mark Haun in Washington state: JPG1, JPG2, JPG3. Mark is using paralleled pairs in a shielded outdoor CAT-5 ethernet cable for the cable between his sensor stand and the indoor switch control module.
Testing and balancing FDM Proton Precession Magnetometer Counter-Wound Coils for Dave Eubanks of Iowa and Alaska JPG, JPG. Balancing was done prior to this picture out in the middle of a room on pair of plastic saw horses and 3/4" sheet of plywood using an Agilent 1733C LCR meter.
NBLNA Module (Narrow Band Low Noise Amplifier) Ver. 0.9.4 ( JPG 0.9.3)
Building and Testing the Analog Board - Partial Draft on NBLNA testing PART V Article Johson Noise Worksheet: See Articles
Detailed NBLNA Assembly Instructions contributed by Carl Olsen PDF, see also, our Nov. 12 NBLNA assembly notes.
NBLNA analog board: Ver. 0.9.2 JPG (October 23, 2010), older Ver. 0.8 JPG Discussed July 17, 2010.
Narrow Band Low Noise Amplifier (NBLNA)
NBLNA Ver. 0.9.4 Schematic PDF
NBLNA Ver. 0.9.4 Printed circuit board PDF
REVISED => NBLNA Ver. 0.9.4 Parts List PDF
Sample Gain measurements PDF, Marked up schematic PDF, and corresponding Johnson Noise Worksheet PDF (see Feb. 15, 2011)
Use resistor noise to characterize a low-noise amplifier, Measure gain or noise with an AC voltmeter, Joe Geller, edited by Martin Rowe and Fran Granville, EDN, June 23, 2011.
SWCTRL Module (Switch Control) Ver. 0.9.1 (0.9.0 JPG )
Operation, Building and Testing the FET-Relay Control Board PART VI Article
Note: Use care that the relay socket pins are all at the same height before soldering. Discard the small signal relay used as the form to align the pins for soldering (Or, open it up to see how it works; we send five with each kit). Use care to not get flux or solder inside the gold pins!
Detailed SWCTRL Assembly Instructions contributed by Carl Olsen PDF
SWCTRL polarization board prototype Ver. 0.8.8: JPG, older versions JPG PDF Discussed April 17, 2010, June 18, 2010
Picture of Relay Socket (gold MillMax pin jacks) PDF Temporary Snubber capacitor: PDF
Zero-Current Switching FET-Relay Hybrid Polarization circuit (SWCNTRL) - Digital Board Switching and Control
SWCTRL Ver. 0.9.1 Schematic PDF
SWCTRL Ver. 0.9.1 Printed circuit board PDF
SWCTRL Ver. 0.9.1 Parts List PDF
Concept Drawing of how the counter-wound coil pair is re-configured from a powered coil for proton spin polarization to a center-tapped counter-wound coil pair to pick up the precession signal with ambient RFI/EMI noise cancellation PDF.
Original notes on the Zero-Current Switching FET-Relay Hybrid Polarization circuit: PDF Discussed April 17, 2010
FDM Magnetometer Flow Charts
FDM Magnetometer Software PART VII Article
Overall measurement cycle: PDF Discussed June 8, 2010
The auto-retry process: PDF Discussed June 6, 2010
Polarization and digitization timing: PDF , the small signal relay "pulls in" before digitization, discussed in comments.
Filtered envelope display: PDF Discussed June 17, 2010 (Revised 9/9/2010, added digital filter left off original dwg.)
SOFTWARE
Copy and Installation instructions (draft). We can send the project files (only with a kit purchase) via email or lately we have been using "Drop Box".
We are happy to share our LabView files (only with a kit purchase) with those experimenters who own a LabView development system (not the usual case). However we are not able to distribute the FDM frequency estimator source code.
MISC
Input common mode filter: PDF Discussed May 29, 2010 (replaced series 50 ohm Rs with one loop through ferrite bead)
Analog output transformer coupling: PDF Discussed April 21, 2010 (dropped output load resistors)
National Instruments Module
NI USB-6008 digitization (ADC) and control module
Connection from the NBLNA analog output JPG to the USB 6008 pseudo differential input JPG.
Connection from the USB 6008 +5 V, com, and digital outputs JPG to the SWCTRL board digital inputs JPG.
Very Important => FDM Magnetometer electronics System Grounding.
Legend for our TXT files:
Date Time F Scalar Larmor FDM FDM FDM Env. Polr. Msrd. Air Fluid
Frequency Ampl. FOM NBS/N Ampl. Time Tau 2 Temp Temp
11/18/2011 9:48:18 AM 53615.88 2282.004 0.808 3E-7 13.7 0.831 0.603 0.737 33.11 35.70
11/18/2011 9:50:29 AM 53615.81 2282.001 0.738 5E-7 23.3 0.778 0.605 0.749 33.09 36.20
11/18/2011 9:52:52 AM 53615.53 2281.989 0.857 6E-8 32.7 0.882 0.632 0.801 33.27 36.91
FOM-figure of merit; NBS/N-narrow band signal to noise ratio; Ampl.-amplitude; Env.-envelope; Polr.-polarization; Msrd.-measured
Project Documentation, Links and References (very early stages)
Safety notice: Generally, no earth grounding is needed at a wood sensor stand. However, if there is any possibility for life threatening electrical potentials and/or currents at your individual sensor stand, than a local earth ground is required for safety reasons, at least when working at the stand. Never disconnect a powered coil when the polarization current is on (there will be a high voltage spike). Also, wear safety glasses and observe good electrical grounding practice for any mains operated power tools while assembling the stand and coil pair. In other words, individual experimenters are solely responsible for their own safety and we (GELLER (Geller Labs) are not in any way responsible for or liable for any injuries incurred while performing this FDM magnetometer experiment. Please do not use our plans or kits if you do not agree to accept full responsibility for your own personal safety.
QUESTIONS/COMMENTS/notice of typos, etc. send email to joegeller @ gellerlabs dot com
COPYRIGHT © 2009, 2010 JOSEPH M. GELLER, All rights reserved.