Sea Tel Base Exit, Quick Start Manual

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Procedure, Field Replacement, Level Cage Kit, Base Exit
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Document No
135266 Rev B
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7. 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). Normal trace is +/ ‐ 1 division
from red line.
8. Azimuth Targeting:
Should the antenna have issues targeting, such as not accurately finding the satellite or repeatedly finding the satellite in
different azimuth positions, then it’s important to ascertain 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, noting that the system points
correctly (bow, starboard, aft, port, bow and starboard) and that no AZ reference error is flagged by the PCU. A
mechanical problem such as the belt skipping on the sprocket, or another physical restriction, could also cause this kind
of error. Skewing the antenna in azimuth by holding the right or left arrow key to drive the antenna slowly may also
present an issue.
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.
9. Drift:
Another failure which can occur is if a rate sensor starts drifting. This means the sensors voltage output deviates from
what the PCU is expecting (2.5VDC), which introduces error into the control loop. It’s more common to see this in the
Azimuth axis as the CL and EL axis have the tilt sensor as their long term reference (although should the rate sensors drift
be large enough to overpower the tilt sensor you would see the system driving into one of the CL or EL end stops).
To verify if the system is drifting in Azimuth turn off tracking and monitor the relative position, under static conditions
(i.e. when the vessels heading isn’t changing), it should remain still. If the relative value begins to increase/decrease from
its nominal position then the azimuth rate sensor is drifting, feeding error into the PCU’s control loop which is causing
the PCU to believe the vessels heading is changing and in turn driving the relative in the opposite direction to
compensate.