[Chipawa]

Many years ago, I used string pots for measuring linear motion of components on Navy ships. We called them "yo-yo pots." I can't speak for cost or availability, but the ones we used we're quite reliable.

One thing I would recommend is to check their linearity. After installation, we would monitor the pot's output at various points along the extension and calibrate our readings. Depending on how exact of a measurement you need, I recommend teams calibrate their yo-yos.

Chip Tucker
Team 1111