Specifications

BATS AND PORTABLE BATS INSTALLATION
2-53
2.4.3 HYDROPHONE-VRU OFFSET
The VRU offset is the difference in angle between the installed hydrophone and vertical (static off-
set). (It can also represent the offset between the Remote Dynamic Motion Sensor and the Hydro-
phone.) Offsets can occur either due to a mis-aligned hydrophone or from changes in trim to the
vessel. The system allows for either manual entry of attitude error corrections or auto correction
via the hydrophone's internal VRU for offsetting the static tilt of the hydrophone/staff. The attitude
(pitch/roll) offsets are error constants that subtract from the remote or external dynamic motion
sensing system data to compensate for the non-vertical installation of the Hydrophone shaft (or
difference between DMS and Hydrophone).
ENTERED OFFSETS: For manual entry the operator must measure the angle of the shaft with re-
spect to vertical and enter the data in the PITCH-ROLL ERROR menu. The vessel should be in a
harbor or at dock to perform this measurement. Pitch and roll errors are entered in degrees. The
system accepts and displays data with a precision of 0.01 degrees.
ORIENTATION: Change the VRU ORI-
ENTATION if the Model 4740A
VRU/Amplifier is mounted on a sur-
face other than bow facing. For ex-
ample, if the arrow at the top of the
unit is pointing towards starboard
then change the ORIENTATION pa-
rameter to starboard.