Browse Prior Art Database

Original Publication Date: 1982-Feb-28
Included in the Prior Art Database: 2004-Apr-03

Publishing Venue

Xerox Disclosure Journal


Errors in rotary digital encoders (transducers) are caused by unequal line pattern spacing for optical transducers and uneven tooth spacing for gear type transducers. In addition, there can be a cyclic error due to the axis of rotation of transducers being different than the axis of the line pattern or gear teeth. The circuit shown above provides an electronic system for correcting both errors. The circuit operates by measuring the time between the reference transition and the unknown (transducer) transition. The digital counter is reset beforeJW enables the counter which counts reference clock pulses for the duration of PW. The number in the counter is phase error, phase LAG/LEAD is the sign (plus or minus) of the error. The FLAG indicates that the reading has been made. Once the phase error for each transducer pulse as a function of position is measured and stored, its value is used as a correction term.