The TRACKER TRK-1TO2 position sensor from New Scale Technologies (Victor, NY) measures 8.5 × 11.5 × 1.61 mm and provides 2-micrometer resolution. It can be used as a linear encoder or off-axis rotary encoder and unlike optical encoders, does not require a light source and is suited for optical imaging.
Specifications include a repeatability of 2 micrometers, a supply voltage of 3 to 6 Vdc, and current of 21 mA. The sensor provides a direct digital output using a standard I2C protocol. It is insensitive to shock, vibration, and particulates.
For more info, contact http://info.hotims.com/22908-307