Small rotations

[ChrisR]

Plastic protractors/angle measuring devices werre suggested not so long ago for measuring knob rotations for focus increments. New to me though are digital ones such as
http://cgi.ebay.co.uk/Digital-Angle-Fin ... 35ada0792e
which claim to resolve 0.1°.
For a common 1mm feed screw that's 0.28 microns, and for a 0.5mm micrometer screw, half that.
It's about 0.5 mm movement of the end of the 300mm "arm". Rather a lot of clearance would be required to get "in range" though.




Or... fixed to a 200 micron per rev microscope fine focus knob, it's one tenth the wavelength of light, per digit...

[elf]

Plastic protractors/angle measuring devices werre suggested not so long ago for measuring knob rotations for focus increments. New to me though are digital ones such as
http://cgi.ebay.co.uk/Digital-Angle-Fin ... 35ada0792e
which claim to resolve 0.1°.
For a common 1mm feed screw that's 0.28 microns, and for a 0.5mm micrometer screw, half that.
It's about 0.5 mm movement of the end of the 300mm "arm". Rather a lot of clearance would be required to get "in range" though.




Or... fixed to a 200 micron per rev microscope fine focus knob, it's one tenth the wavelength of light, per digit...

austriamicrosystems makes rotary magnetic encoders that can resolve .08 degrees, so .1 should be easier
http://www.austriamicrosystems.com/eng/ ... c-Encoders