Af - Field Calibrate Compass; Ar - Return To Factory Calibration - Teledyne WORKHORSE Operation Manual

May 2015
AF – Field Calibrate Compass
Purpose Calibrates the compass to remove hard and soft iron effects.
Format AF
Recommended Setting. Use as needed.
Description The built-in automated compass calibration procedures are similar to the alignment veri-
fication, but requires three rotations instead of one. The H-ADCP uses the first two rota-
tions to compute a new calibration matrix and the third to verify the calibration. It will
not accept the new matrix unless the calibration was carried out properly, and it asks you
to verify that you want to use the new calibration if it is not as good as the previous cali-
bration. While you are turning the H-ADCP for the two calibration rotations, the H-ADCP
checks the quality of the previous calibration and displays the results. It compares these
results with the results of the third calibration rotation.
There are two compass calibrations to choose from; one only corrects for hard iron while
the other corrects for both hard and soft iron characteristics for materials rotating with
the H-ADCP. Hard iron effects are related to residual magnetic fields and cause single cy-
cle errors while soft iron effects are related to magnetic permeability that distorts the
earth's magnetic field and causes double cycle errors. In general, the hard iron calibration
is recommended because the effect of hard iron dominates soft iron. If a large double cy-
cle error exists, then use the combined hard and soft iron calibration.
For details on compass alignment, see
AR – Return to Factory Calibration
Purpose Returns to the factory calibration matrix.
Format AR
Recommended Setting. Use as needed. TRDI strongly recommends sending the AR command
(compass restore) before the AF (field calibrate) command. This is done to prevent corruption of the
calibration matrix due to a previous incomplete compass calibration.
Description If the calibration procedure is not successful (AF-command), return your H-ADCP to the
original factory calibration, by using the AR-command. Try using the AR-command if you
have trouble calibrating your compass. In some circumstances, a defective compass cali-
bration matrix can prevent proper calibration.
Page 128
EAR-Controlled Technology Subject to Restrictions Contained on the Cover Page.
Compass Calibration.
WorkHorse H-ADCP Operation Manual