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Field Service Procedure – Replacement PCU Kit, ST88, ST94 & ST144
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Document No
137738 Rev A
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10. Rate Sensor Monitoring:
Rate sensor outputs can also be monitored using the DISP_W screen of DacRemP to verify any deviations under static
conditions. The traces should remain consistent; any drifting or spikes are an indication the sensors voltage output is
changing and the sensor is defective (provided no forces are being exerted on the system).
11. Azimuth Targeting:
Should the antenna have issues targeting in azimuth, such as not accurately finding the satellite or repeatedly finding the
satellite in different azimuth positions, then it’s important to diagnose if the system is mispointing in azimuth or relative.
Relative feedback from the AZ encoder can be verified by initializing the system, verifying it calibrates itself correctly,
and then driving the pedestal clockwise in 90 degree increments over a 360 degree rotation. Note that the system points
correctly relative to the vessel and that no AZ reference error is flagged by the PCU. A mechanical problem such as the
belt slipping on the sprocket could also cause this kind of error.
If the system keeps finding the satellite at different azimuth positions but at the same relative, then the encoder is
functioning correctly and the azimuth rate sensor is calculating the movement incorrectly causing the antenna to
mispoint.