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blog:yg_elevation_offset_measurement_investigation_13_may_2011

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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