Ideas for magnetometer torsion thread

First, you have to get the bucket underneath.

-- "For a successful technology, reality must take precedence over public relations, for nature cannot be fooled." (Richard Feynman)

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Not in my time. The Cambridge Instruments that made galvos was taken over by the George Kent Group in 1968, which split off all the profitable bits and floated the loss-making electron microscope part of the business as Cambridge Scientific Instruments in 1974 (when I was working for the George Kent Group in Luton). It sank, and merged with Metals Research of Cambridge, which also sank and was eventually rescued by one Terence Gooding in 1979, who owned it when I worked there from 1982 to 1991.

We got our specialty metals from Goodfellows

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-- Bill Sloman, Nijmegen

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The largest all glass fiber optic fiber you can get. Leave the plastic coating on to reduce moisture effects.

?-)

Or, if there's big money sailboat racing nearby, you might also get strands of kevlar and carbon fibre. These might also be had from car or aircraft or bullet absorbing vest R&D places.

How long a strand do you actually need?

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I once thought glass was a really, really thick liquid. These people mocked and ridiculed me until I changed my mind:

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About 4 inches, or a bit more, depending on the way of attaching the strand. I'm working on changing the attachment method right now.

I have a RC model hobby shop nearby and I plan to check if they sell fiberglass cloth - but first have to figure out the attachment.

Thanks,

- Alex

I would suspect both Kevlar and carbon fiber to be more sensitive to humidity and temperature effects than glass.

--
www.wescottdesign.com

When you're in that shop buy a bottle of CA glue (think of it as superglue that actually works) and maybe some sticks. Wrap the glass fiber around a stick, and adhere it with a drop of glue. If you arrange things so that the fiber goes up and over the stick after it is glued then it'll be stronger, as you won't be forcing a huge bend right at the glue joint.

Or put a dot of glue on the side of the stick near the end and lay the fiber on the glue dot, on the stick axis.

--
www.wescottdesign.com

.003" shim stock (and thinner, too) can be had from McMaster-Carr and other machine tool supply outfits. The maker is "Precision Brand" and you can get 6" x 100' rolls. You can also get sheets that might be

12" square. You can then figure out a way to slice off a narrow ribbon from the edge.

Jon

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I figure a thin strong wire of

Half-thou 304 shim stock is easily availabe. At 40k PSI to yield, 20 thou wide would hold around a couple hundred grams.

Best regards, Spehro Pefhany

--
"it's the network..."                          "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

There are several problems with using any metal. One is that temperature changes the length and width. Quartz has a coef. of thermal expansion that is much less than any metal ( possible exception is invar . but as I remember quartz expands less than invar ). Another problem is hysteresis. You apply a force to a metal strip and it deflects. Remove the force and the metal strip does not return to it's original position. Quartz is about a 1000 times better at returning to the original position. Quartz fiber is also very strong. If the diameter is small, quartz fiber is stronger than steel.

Dan

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Yes, quartz is far better in every respect--t.c.e, immunity to humidity & induced currents, internal friction, hysteresis, and strength.

In every respect, that is, if he has it. :-)

-- Cheers, James Arthur

If you are looking for magnetometers, you might also look at Bill Slomans thread: Precision Hall effect sensors

-- Regards,

Adrian Jansen adrianjansen at internode dot on dot net Note reply address is invalid, convert address above to machine form.

Oh please, his head will explode! It's already larger than life!

Jamie

what diameter and length did you try? One strand of litz wire sure is thin, and suspending a wire 2 stories high in the stairwell would certainly improve flex.

NT

That's the hard bit, suspension strip came in .003" *wide*, by various thicknesses, down to below .001". I still have the vernier-sleeve .0001" micrometer I had to get to measure the goddamn stuff. You can watch hand heat expand the stirrup if you hold it wrong.

I'd have loved to have seen how they made .003" by .001" strip.

--
"For a successful technology, reality must take precedence 
over public relations, for nature cannot be fooled."
                                       (Richard Feynman)

Probably from wire, in a rolling mill. You can get very precise hand-operated rolling mills for pretty cheap.

Cheers

Phil Hobbs

Not much risk of that. Jamie may over-estimate the dangers posed by positive references - he doesn't seem to have had much experience of coping with them.

-- Bill Sloman, Nijmegen