Well, here are three more manufacturers (the third and fourth show
single axis as cots equipment, but you might be able to work with them
on a triaxial version, or they should be able to direct you to someone
who can do it for you):

http://www.ets-lindgren.com/page/?i=HelmholtzCoils
http://oersted.com/helmholtz_coils_1.shtml
http://www.gmw.com/electromagnets/Electromagnet_index.html
http://www.maginst.com/specifications/helmholtz_coils.htm

This person seems to have some experience building and characterizing them:
http://www.chwala.de/hh3eng.html

Depending on your specific needs you might try using a consultant.

This company seems to have some experience in building and
characterizing them as well:
http://www.magnetometer.com/helm.php
though no COTS versions.

Other links of note:
http://www.directindustry.com/prod/stl-systemtechnik/portable-helmholtz-coil-system-28144-99889.html

Interestingly,
http://oersted.com/magnetic_viewing_film.shtml
has magnetic viewing film that looks to be cheap enough for fun and
experimentation... ( -you faintly hear sounds of Adam tucking that
link away for future use- )

Out of curiosity, what's the application?  Why don't you build one
yourself and use a fluxmeter to calibrate it?  A NASA article (
http://www.nasa.gov/offices/oce/llis/0671.html ) gives enough details
on a particular design that you could readily replicate their results
as a starting point.

You could even use a (relatively) cheap three axis magnetometer to add
closed loop feedback to a control system for the coil.
http://www.sparkfun.com/commerce/product_info.php?products_id=244

-Adam

On 8/5/08, Jonathan Hallameyer <jmhtau@gmail.com> wrote:
> The second manufacturer there is one that Ive already emailed for more
> information, and the first manufacturer site looks like it hasnt been
> updated in a while, but I'll try to contact them.
>
> On Tue, Aug 5, 2008 at 12:59 PM, M. Adam Davis <stienman@gmail.com> wrote:
> > A google search
> >
> > http://www.google.com/search?q=helmholtz+coil+three+axis
> >
> > Brings up two manufacturers on the first page:
> >
> > http://www.meda.com/Data_Sheets/hcs01.pdf
> >
> > http://www.laboratorio.elettrofisico.com/eng/products.asp?famiglia=Instrumentation&sottofamiglia=HELMHOLTZ%20COILS
> >
> > Looks like the larger fields are custom designs, but perhaps the
> > smaller fields available in the second link are "off the shelf" items.
> >
> > -Adam
> >
> > On 8/5/08, Jonathan Hallameyer <jmhtau@gmail.com> wrote:
> >> Hello All,
> >> I'm looking to buy a tri-axis helmholtz coil system and having a bit
> >> of difficulty finding manufacturers of such systems with google, The
> >> Ive found a couple, but the majority of the results are technical
> >> papers and links to patent sites. Anyone know of any manufacuturers,
> >> or a better search engine to use? Ive tried globalspec but that
> >> returns nothing at all for "helmholtz"
> >>
> >> Thanks,
> >> Jonathan Hallameyer
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