WorkHorse Sentinel User's Guide
page 20 RD Instruments
9 Compass Calibration
The main reason for compass calibration is battery replacement. Each new
battery carries a different magnetic signature. The compass calibration al-
gorithm corrects for the distortions caused by the battery to give you an ac-
curate measurement. You should be aware of the following items:
• We recommend against calibrating the WorkHorse while on a
ship. The ship’s motion and magnetic fields from the hull
and engine will likely prevent successful calibration.
• If you think your mounting fixture or frame has some mag-
netic field or magnetic permeability, calibrate the WorkHorse
inside the fixture. Depending on the strength and complexity
of the fixture’s field, the calibration procedure may be able to
correct it.
NOTE. If you will deploy your WorkHorse looking up, calibrate it looking
up. If you will deploy it looking down, calibrate it looking down.
9.1 Preparing for Calibration
a. Place the WorkHorse on a piece of strong cardboard on top of a smooth
wooden (non-magnetic) table. If a wooden table is not available, place
the WorkHorse on the floor as far away from metal objects as possible.
Use the cardboard to rotate the WorkHorse during calibration—this way
you will not scratch the WorkHorse.
b. Connect the WorkHorse as shown in “Setup the WorkHorse Sentinel
ADCP,” page 11.
c. Start DumbTerm. See the RDI Tools User's Guide for assistance on
using DumbTerm.
9.2 Compass Calibration Verification
Compass calibration verification is an automated built-in test that measures
how well the compass is calibrated. The procedure measures compass pa-
rameters at every 5º of rotation for a full 360º rotation. When it has col-
lected data for all required directions, the WorkHorse computes and dis-
plays the results.
NOTE. Verify the compass if you have just replaced the battery, memory
module, or any ferrous metals is relocated inside or around the WorkHorse
housing.
Start the test with the AX-command and follow the instructions. Place the
ADCP in the same orientation as it will be deployed. The WorkHorse
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