Hi Mike and other flux gaters,

> In all the excitement regarding magnetic direction devices, has anyone
> mentioned fluxgate devices with arc-minute accuracy? (specious claim -
> indefensible really).
> I read Electronics and Wireless World 5 years back now, got the kit and
> built one sensitive to micro-gauss for monitoring the earths magnetic field
> for incipient aurorae.

Time flies, it was in 1991.

> The company supplying the coil, Telcon metals, still exists as far as I know
> and thus so should the supplier of the kit. It strikes me as being the
> perfect thing for a PIC project. What's more it has a follow-up article
> using it as the core of an electronic compass. In the kit you use an
> oscillator and dividers to drive a square way across a coil and pick the
> saturation effects up using orthogonal sense coils on the rising and falling
> edges of the excitation wave. To drive it with a PIC and transistor array-
> too easy sir. What *and* use an 8 bit ADC to measure the  output signal ?

Sounds like the ideal Job for the 16C711 chips I have waiting here.
I have already wound my core according to the instructions in the
second article but never had the time to build the drive circuitry.
Might be the ideal use for a PIC, get everything into two ICs, one
PIC and one OP-AMP.

> Given a sufficient kick I may even bother to dig up the reference.

I will save you the trouble, they live in my navigation file.

The First Article appeared in September 1991 Electronics World +
Wireless World

The second in January 1992 issue

Last contact I have for Telcon is
   Telcon metals Limited
   Napier Way
   Crawley
   West Sussex
   RH10 2RB
   UK

   +44 (293) 28800
   +44 (293) 36904  (fax)

They did not sell direct to the public at the time I looked into this
project.  They have a distributor in South Africa called Spectratech
or more commonly these days Elvey International but I don't think the
cores recommended for the flux gate are any common part though I may
be wrong now.  I managed to get a similar core from Spectratech in 1992
but never did more than drive it with 50 Hz signal to look at the outputs
and watch in awe as the wave shapes on the sence coild changed as one
moved a screwdriver in the vicinity.

There is also a British Standard BS5935 or the IEC 635 that is titled
   Torroidal strip-wound cores made of magnetically soft material.
This makes for pretty weak reading but it does have one or two
formulas for calculating the window area and such.  Also mentions
the recommemded core aspect ratios but little else that is usefull.

> M. Harrison                                     TEL 44 1235 445288

Perhaps you could find out if Telcon have a UK or US retail outlet.

Cheers
--
Kalle Pihlajasaari   kalle@ip.co.za   http://www.ip.co.za/ip
Interface Products   P O Box 15775, DOORNFONTEIN, 2028, South Africa
+ 27 (11) 402-7750   Fax: 402-7751    http://www.ip.co.za/people/kalle

DonTronics, Silicon Studio and Wirz Electronics uP Product Dealer