Measure swim speed

[vuk]

Hello!

I would like to measure swimming speed.

Swimmer pulled the rope and I would be interested in continuing changes in speed swimming.

rope is on the pulleys,put up..

what do i need for realize this measurement?? hardware what kind?

i have idea but i don't know how can i connect measurements with computer.

thanks....

[falkpl]

Could put an encoder or just an indexer on the pully and count revs.  Very inexpensive solution given your setup.  You can get X(t) and calculate v(t) a(T) assuming a single direction of swim.  Vision would probably be easier depending on situation.

[vuk]

Yes,it's for measurement in one way (25m-50m).

How can i connect encoder on my computer? (it's my first practical problem that i'll solve). My question is there any system encoder for this things for labview?what kind of encoder which would be required?

thanks

[falkpl]

easiest case is to use a hall sensor and count revs with a counter.

You can use a quadrature encoder, many counter boards can handle the encoding, your resolution is then 2000 or more times greater but probably not needed since I assume the pully is small.

Vision is also an easy method.  set up a camera to view the swimming lane, have the swimmer pull a small float of a distinct color or even use the swim cap color as your marker.  You can translate the position of the marker to position in the pool.