Rotary optical quaderature encoders like the agilent HEDS series lack fine accuracy because of eccentricity in the mounting, the motor bearings, and the dimensions of the interacting parts. A back of the envelope calculation reveals the effect of eccentricity.
For 10 thou of eccentricity, with a radius of .5 inches:
ErrorAngle = Eccentricity*(360/2*pi*r)= 1.145 degrees of error
For 1 thou, (which would be very hard to achieve) there would be 0.1145 degrees of error
Which may be acceptable in some situations. Plus, these encoders have very good repeatability. But what if accuracy is desired? The error could be mapped, however this requires special equipment. I have also heard of methods that use two encoder read heads instead of one.
I am looking for some sort of alternative to this that will provide better accuracy when mounted to a motor. What sorts of encoder products exist that tackle this problem?
For 10 thou of eccentricity, with a radius of .5 inches:
ErrorAngle = Eccentricity*(360/2*pi*r)= 1.145 degrees of error
For 1 thou, (which would be very hard to achieve) there would be 0.1145 degrees of error
Which may be acceptable in some situations. Plus, these encoders have very good repeatability. But what if accuracy is desired? The error could be mapped, however this requires special equipment. I have also heard of methods that use two encoder read heads instead of one.
I am looking for some sort of alternative to this that will provide better accuracy when mounted to a motor. What sorts of encoder products exist that tackle this problem?