Frank said:
"Roger Hamlett" <
[email protected]> schreef in bericht
[snip]
encoders-uk. Two things limit the resolution. The disk size (obvious),
and
the support accuracy of the shaft. If (for instance), you have a 50mm
encoder disk, running full quadrature decoding on a 36000ppr disk (giving
potentially 144000 positions), The steps at the edge of the disk,
correspond to just 1um, and if the shaft moves laterally by this amount,
the count will change. Hence the high accuracy units have very tight
specifications on the shaft loadings, and use very expensive bearing
designs...
Then there are absolute sin/cosine wave encoders, no steps are
lost, thanks to their absolute nature.
Here's a nice encoder:
http://www.usa.canon.com/html/industrial_encoders/x1mnonrot.html
230 million pulse per revolution, no less
Looks nice, but it really worries me when I see a spec for something like
resolution quoted to 4 significant digits accuracy. Implies that the
writer knows nothing about what figures mean.
--
Regards,
Adrian Jansen adrianjansen at internode dot on dot net
Design Engineer J & K Micro Systems
Microcomputer solutions for industrial control
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