AVR-Chat

On Thursday 11 March 2004 01:05, Dave VanHorn wrote:
> >So you see, the biggest problem in accuracy is to positionning
> >exactly the sensors.
> >Far distance between the sensors, better accuracy.

> Matching the optos will also be a problem. They aren't known for
> speed either, though that's solveable.

> Breaking tensioned wires might be a lot easier and more repeatable.

Erm... no ... not unless you're drawing your own wires or carefully
selecting the wires from a large spool. A few percent difference in
wire diameter "dramatically" changes its physical strength.

An old photography trick is to stick a microphone on a playing card;
with the microphone hooked up to an amplifier with the gain set to a
"critical" level in order to set off an electronic flash; then fire
the bullet through the card.

Of course it's useless doing that if you want to measure the speed
of the bullet because you slow it down by piercing the card.

I've thought of using a soap bubble instead; triggering when the
refraction through or reflection from the bubble changes. 

Make sure that the air isn't moving too much around the test
cell to avoid false triggers.

-- 
/"\ Bernd Felsche - Innovative Reckoning, Perth, Western Australia
\ /  ASCII ribbon campaign | I'm a .signature virus!
 X   against HTML mail     | Copy me into your ~/.signature
/ \  and postings          | to help me spread!