Sentinel V SC and RT Operation Manual
September
2017
EAR-Controlled Technology Subject to Restrictions Contained on the Cover Page.
Page 113
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At high dip angles (which occur at latitudes near the magnetic poles) special care must be taken
when calibrating the Sentinel V compass. First, the system must be tilted at a higher angle to en-
sure that the calibration points provide good coverage of the X, Y, and Z axes. Second, and possi-
bly more important, is that at high dip angles the component of the magnetic field used to deter-
mine heading becomes very small. As such the Sentinel V compass becomes highly sensitive to
any external influences seen during calibration, so it is important to ensure the calibration is per-
formed in the most magnetically “clean” environment possible. TRDI recommends that if you
are having trouble calibrating the Sentinel V compass that you move the system and/or ensure
the area around the system is clear of electrical equipment and ferrous materials.
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The precision of the heading during calibration is not as critical as the tilts. Headings can be off
by 10 degrees or more for any step. “By hand” and “by eye” calibrations are possible. The tilt an-
gle precisions during calibration are important and should be followed as close as possible.
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If you are not using a calibration fixture, then having two people, one holding/rotating the Senti-
nel V, one controlling the computer, makes the compass calibration much easier.
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The Sentinel V checks for stability before it takes a calibration point. It should be held still in
each position until the point is taken. There can be a delay in the acquisition of a calibration
point after the Take Sample button is clicked. If the Sentinel V moved during the sample point,
cancel the calibration and start over.
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The Sentinel V cannot be adequately calibrated without tilting the system during the compass
calibration. A single plane calibration is not advised.
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The Sentinel V should be calibrated in the same orientation (beams-up/beams-down) as it will
be deployed. Failure to do so will cause a 2 to 4 degrees RMS error on the compass reading
which is outside of the specified heading accuracy for the Sentinel V.
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Calibration data points can be taken out-of-order if desired.
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The Sentinel V compass should be calibrated while mounted to the system or mounting structure
whenever possible. The compass can negate hard and soft iron errors, but only if they are ac-
counted for in the calibration.
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The last compass calibration score is shown on the first screen. If the last compass calibration
resulted in a failed condition, it will show as Restored to Factory defaults.
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If you calibrate the compass and obtain a passing score and then try a second calibration and end
up getting a lower score, there is no way to go back to the first calibration.
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If the compass calibration results in a “fail” condition, ReadyV will automatically reject it and
restore the factory calibration.
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The Sentinel V compass should be calibrated after all battery changes.
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Remember that the Sentinel V will time out if no keys are pressed for five minutes and will power
down after waiting five more minutes. If the compass calibration freezes, check the wireless con-
nection. Use the Touch Sensor to restart.
