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blog:yg_elevation_offset_measurement_investigation_13_may_2011 [2011/10/26 06:37] (current)
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 +====== Yg elevation offset measurement/​investigation 13 May 2011 ======
 +Notes from Brett Reid:
 +I Drove antenna to position setpoint Az/El -200,10
 +Randall measured from a point on lower rim of dish to a pont on heatshield edge. 3388mm
 +Drove to Az/El -200,10.1 degrees
 +Measured distance again. 3399mm
 +Determined a change of 0.1 degrees in El produces a 11mm change in length.
 +The tape measure length method is repeatable. It can be used as another check for elevation offset checks with time.
 +Repeated finger pressure to encoder coupling torque test. No movement of pin felt and no change in length of rim to heatshield measured while tracking azel -200,10.
 +We have confirmed small pin is tight.
 +With e-stop engaged the encoder was removed.
 +No looseness of coupling to encoder shaft was felt.
 +Encoder put back on.
 +Adjusted encoder orientation for current elevation position to read as close as possible as before. 0.04 less was the change in elevation reading. Jamie or Jim need to point on a source to confirm this and adjust the offset accordinly.
 +We would have changed parameter 20.21 to produce 3388mm rim to heat shield with position -200,10 (azel) setpoint but I forgot the key parameter and would not have been able to change it.
 +The current heatshield to rim measurement after commanding -200,10 azel degrees is 3392mm, a change of 4mm after encoder checking/​reinstall.
 +Thanks Randall for doing the checks.
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