[TAlholm]

Originally Posted by Ernst

Do you have more details on the application? Is the sensor attached to something moving or is it measuring something else that's moving? Are you driving an elevator or measuring distance driven on the ground?

I'd be inclined to go with a potentiometer or encoder if you have anything rotating relative to the linear motion, like a motor spinning a shaft to drive an actuator or belt, or a tracking wheel spinning on the ground.

Are you measuring to a moving plane? An ultrasonic sensor might work.

I'm experimenting with a method that may allow faster and safer rehab for people with arm or leg injuries or who recently had surgery. For safety of the user, I am staying away from tracking rotation.