For a thesis project for ways to localize a slide on a linear rail with a length of ~1m. The slide in question is the seat of an indoor rowing machine: Concept2 Ergometer Price is definitely an issue as we want to built multiple sensor setups.
I need the location of the slide with an accuracy of around 1mm with a rate of 50-100Hz. Adding cables to the seat is something I want to avoid, so I'd like to have an external sensor (fixed to the rail) and at most a target (e.g. reflective surface) on the slide. Seat speed can be up to 2m/s.
I thought about Sharp triangulation sensors (like the GP2Y0A60SZ0F), but I have no experience with the accuracy and its behavior with fast moving objects. Even when operator with 5V, the output for 50cm and 1m only differs by 0.25V so I assume that there is a major accuracy degradation.
Ultrasonic is to slow and inaccurate, and commercial laser triangulation sensors are quickly at >200$.
Which sensor principles am I missing? As soon as I know what I'm looking for, I can find a sensor on my own (no shopping question!), but I can't search for a sensor if I have no starting point.