So why not take a higher-tech approach?
Use magnets on your moving parts with high resolution magnet sensors such as Austria Micro Systems AS5048A.
Adapter/demo boards:
http://www.ams.com/eng/Support/Design-Resources/Demoboards/Magnetic-Position-Sensors/Magnetic-Rotary-Position-Sensors/AS5048A-DK-AB
http://www.ams.com/eng/Support/Design-Resources/Demoboards/Magnetic-Position-Sensors/Magnetic-Rotary-Position-Sensors/AS5048-DK-ST
http://www.ams.com/eng/Support/Design-Resources/Demoboards/Magnetic-Position-Sensors/Magnetic-Rotary-Position-Sensors/AS5048A-EK-AB-STM1.0
AS5048_1.3[1].pdf (1.2 MB)