See site for details of suitable fluxgate 
>sensors:- http://fqs.dconn.com/Electronics/sensors.htm 
>    Descriptions of amateur constructed fluxgate equipment have been 
>published. Magnetic field changes may be of interest to Ham Radio operators 
>and to astronomers.
>
>     Regards Chris.
>
The sensors that Fat Quarters sells are probably not fluxgate sensors.
The are most likely magneto inductive sensors. Precision Navagation 
http://www.precisionnav.com/sensormain.html holds
some patents on this technology. See
http://www.patents.ibm.com/patlist?icnt=US&patent_number=4851775
and http://www.patents.ibm.com/patlist?icnt=US&patent_number=5239264

Also this link has a brief description of the operation of the
 magneto inductive sensor.
http://www.pacific.net/~brooke/Sensors.shtml#Magneto-Inductive

Jim Hannon
http://soli.inav.net/~jmhannon/
42,11.90N,91,39.26W
WB0TXL


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