> >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 ? I seem to recall that fibre optics attenuate light in proportion to the radius through which the fibre is bent. Perhaps winding a fibre around an elastic tube -- gum rubber surgical tubing comes to mind -- would make a sensor that when wrapped around the subject's chest would be able to measure movement as a change in transmissitivity. Of course it might be a bit simpler to just measure the change in pressure within the tubing. Put the tubing around the subject's chest. Pressurize the tubing slightly to get a reading on a gauge and then watch it fluctuate. Just ideas... Cheers, Win Wiencke Image Logic Corporation ImageLogic@ibm.net