I am selling a really nice string pot on Ebay. For those who don't know what a string pot is, here is an explanation. A string pot is a multi-turn potentiometer with a "string" around it's shaft. When you pull on the string, it turns the pot and you can measure linear distances by coorelating the voltage on the potentiometer with the distance the string has extended. The pot has a spring return. The string pot I have on Ebay is an instrument grade device with a stainless steel "string" enclosed in bellows to keep dirt and debris out of the potentiometer.
I would think it would be a great way to provide position feedback for robot applications that need to measure distances up to 2 feet.
If you would like to see it, go here:
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or look for stringpot on ebay