WorkHorse Mariner ADCP User's Guide
page 18 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.
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. Place the ADCP in the same orien-
tation as it will be deployed.
NOTE. If you will deploy your Workhorse looking up, calibrate it looking
up. If you will deploy it looking down, calibrate it looking down.
CAUTION. If you calibrate the compass in one direction (up or down) and
deploy the ADCP in the opposite direction (i.e. calibrate it in a downward
position and deploy it in a upward position) the compass calibration will be
invalid. Compass errors in excess of 5 degrees may occur.
b. Connect the Workhorse as shown in “Setup the WorkHorse Mariner
ADCP,” page 13.
c. Start BBTalk. See the RDI Tools User’s Guide for assistance on using
BBTalk.
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