Hi, looking for suggestions to meaure the rotation in a spinning speaker. There are two spinning elements I need to measure seperately. One is the bakelite horn, like this: http://users.sa.chariot.net.au/~dna/gif/leslie_slo.gif
There is also a rotating wooden drum on the bottom: http://en.wikipedia.org/wiki/File:Leslie_Speaker.jpg
Putting anything too heavy on the rotating parts will disrupt the balance, so I was thinking optical, like put a strip of whiteout on the horn and drum??? I suppose I could get away with glueing a small magnet or aluminum to the parts.
Hall sensor? Optical?