Azimuth encoder1,2 failures


encoder failures(that i've recorded)
10apr17: az enc1 fault. value jumps by > 1000 deg. need to reset with az pointer.
11oct16: testing when system returns to enc1 after enc1 fault.
10oct16 az encoder 1 fault 15:00 to 07:00 next day.
02oct16 az encoder 1 replaced
10jan16 az encoder 1 replaced
22jun15 az encoder 1 replaced
23jan12: az encoder 1 becomes loose
17jan13: az encoder 2  replaced
xxaug09 az encoder  1 multiple encoder errors
11apr07: az 1 encoder. 2 faults.
08apr07: az 1 enocder fault.
04apr07: az 1,2 encoders reset. broken cable in cable drape.
14nov06: az 1 encoder fails. replaced
14oct06:  az 1 encoder interface board zapped by lightning
09mar06: az 1 encoder replaced. it had jumped on 07,08mar06.
11nov05: az 1,2 encoder faults. replaced enc 1,  13,14nov enc1 faults again. enc2->enc1. 16nov05 replaced enc2
14oct03: az 1 encoder jumps by 3 teeth,
15sep02: az 1 encoder jumps.

azimuth Encoder failures:

    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).
    When encoder 1 fails, the vertex system automatically switches to encoder to for the pointing. This causes a degradation in the pointing since the encoder 1 and encoder  2 values vary as a function of azimuth. This is caused by the "out of roundness" of the azimuth encoder rack gear as well as the bending of the azimuth arm.
    After vertex system will continue to use encoder 2 for pointing until the encoder 1 error is cleared. The error can be cleared by:
Note: 11oct16
    The telescope may get a motion failure and stop tracking during the reset if the difference between encoder 2 and encoder 1 are large enough (the software sees a large jump in the position and then stops). In this case pntpwrdip will try to restart the tracking.

    The plots show a jump in the azimuth position while clearing an encoder1 fault (.ps) (.pdf):


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