SonTek
ADP Software Manual Version 6.42 (November 1, 2000)
20
SECTION 4. Compass Calibration (COMPCAL)
This program is provided with the ADP software to allow the user to calibrate the internal
compass/tilt sensor. Calibration minimizes the effects of ambient magnetic fields on compass
data. We recommend that a compass calibration be performed before each deployment.
This program gives a graphical display of instrument orientation that can insure the compass/tilt
sensor is functioning correctly. The program is intended to be self-explanatory; simply type
“COMPCAL” at the DOS prompt for operating instructions. To run the calibration program,
make sure that the instrument is powered up and connected to a computer serial port and type one
of the following commands:
COMPCAL <com port>
COMPCAL <com port> <baud rate>
where
• <com port> is the serial port number to which the ADP is connected (1 for COM1 or 2 for
COM2).
• <baud rate> is the communication baud rate setting of the ADP; if no value is given, the
program assumes the default setting of 9600 baud. Acceptable baud rate settings are 1200,
2400, 4800, 9600, 19200, 38400, 57600, and 115200.
Once started, the program shows a graphical display of compass orientation. At this point, the
compass is not in calibration mode; it is in a monitoring mode where orientation data is output in
real time. The graphical display provides three perspectives. To the right is a compass that
indicates the direction the X-axis is pointing. To the left are tabular and graphical displays of
pitch and roll. In the center is a 3D box with an X on the side corresponding to north. When this
side is facing into the screen, the instrument X-axis is facing north.
To begin the calibration, press the F1 key. The program will pause to put the compass in
calibration mode; following this, the display will resume and the program provides instructions
for instrument rotation at the bottom of the screen. Rotate the instrument slowly through two
complete circles, while varying the pitch and roll as much as possible. Each turn should take
about one minute; the exact starting and ending orientations are not important.
To end the calibration, either press the F1 key again (to remain in the graphical display) or press
the ESC key to exit with the calibration results. Pressing ESC at any time during this program
will exit the program and display the results of the most-recent calibration. Refer to the ADP
Operation Manual for more information about compass calibration and for information on how to
interpret the calibration score.
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