Azimuth encoder difference


    There are two azimuth encoders. Encoder 1 is on the gregorian side and is used for pointing. Encoder 2 is on the carriage house side and is used to measure azimuth pending (as well as a check on the gregorian side encoder).
    On 09mar06 an azimuth spin was done from az=-90 to az=+270 and then back at slew rate. The encoder difference (Enc1-enc2) was sampled once a second.

    The first plots show the encoder difference versus azimuth (.ps) (.pdf):

    There is a positive going bump in the encoder difference at az=160 degrees and a corresponding negative going bump 180 degrees away. On 21jan00 the runout of the azimuth encoder rack gear was measured. It showed that the azimuth encoder rack gear was bowed inward (by about 1 inch) around an azimuth of 160 degrees (unfortunately the computed azimuth error was off by about a factor of 10!).
    The next plots show the repeatability of the azimuth encoder rack gear error (.ps)  (.pdf): The data and the fit is stored in the idl save file encDifFit.sav .
processing: x101/060309/