This report describes how to build the electronics for a resolver-based absolute angular position encoder for use on a telescope. This system is now in use on the VLA radio telescope azimuth and elevation positioning. The circuits are ideal for upgrading an existing encoder system to one with higher resolution or higher reliability. The report includes schematics, board designs, program source code, and excruciating detail about the design.
Be sure to check Appendix E - Errata. All the errors here have been corrected in the Production Version.
This upgrade to the VLA encoders provides 0.08 arcsecond (0.00002 degree) resolution at low power and high reliability while minimizing RFI emission.
Printable version, but no schematics or board designs (download these seperately): encoder.ps 385KB.
VLA Technical Report No. 76
Absolute Position Encoder Electronics Upgrade
February 18th, 2000