Christoph Klein wrote:
>
> Maybe a little ot ...
> I'm trying to measure the expansion of chest during
> breathing using a pic (there You are ;-) )
> How would You measure a span of about 10cm ?
> Usually flexible rubber tubes with quick silver are used,
> the change of lenght is measured by taking the resistance
> with a wheatstone bridge. only, Hg on the floor can be hard
> to hunt ;-) (and sooner or later it gets there ...)
>
> The device should be rather small and to be attached
> to a person easily. And it should be as "electronical"
> as can be, that is: preferably no mechanical parts ...
>
> Any ideas?
>
> Christoph

Hi,

   I've read quite a few of the suggestions, so here's mine. Why not use
a straightforward measuring tape marked with 0.5mm wide lines, and an
optical sensor?

The best way I know of to maintain tension on the tape is a 'tensator
spring'. This is a pair of rollers with a coiled steel spring wrapped
around them. Unfortunately I don't know where to get them from since
I've changed jobs.

By making the tape a little too long and anchoring it on the measuring
device it should be straightforward to apply and remove.

If this sounds like a sensible solution, mail me and I'll try and send a
sketch.

Keith.