B&G Hydra 2000, Руководство пользователя

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Hydra 2000 User Manual
Part 3 - Calibration
HB-0844-02
3-4
3.2 BOAT SPEED/LOG CALIBRATION
3.2.1 Principle of Log Calibration
To calibrate the log it is necessary to work out the number of
revolutions of a paddle-wheel, or sonic pulses per second that
correspond to each knot of Boat Speed. The Boat Speed/Log
calibration value is always shown as Hertz/Knot (Hz/Kt).
The Hydra 2000 allows you to calibrate both a single or a dual
sensor unit. Under normal circumstances with a sensor mounted
on the centreline the single calibration value should be all that is
required.
However, if the sensor unit is not installed close to the centreline,
or if dual paddle-wheels are installed, then calibration on each tack
will be necessary. The Hydra 2000 will always use the calibration
value for the leeward paddle-wheel/sensor, using the heel angle if
it is fitted or the Apparent Wind Angle if it is not.
3.2.2 Preparation for Log Calibration
Before calibrating the log you should ensure that the underwater
unit is correctly aligned as follows:
Paddle-wheel - The moulded arrows on top of the unit
must be pointing forward along the fore and aft line of the
hull. The unit must also be totally free of any weed or
other fouling.
Sonic Speed - Check that the unit is operating correctly
as per the owner's manual.
3.2.3 Calibration Runs
Consecutive runs, under power, at a constant speed, should be
made over a known distance. To eliminate the effect of tidal
conditions, it is advisable to perform at least two runs, preferably
three, along the measured track.
There are three available options for calibrating the log,
Automatically (AUTO CAL), Manually (MANL CAL) or Reference
(REF CAL).