Nortek DVL 1000 300m, Руководство пользователя

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Appendices 29
© 2017 Nortek AS
where no measurements take place, to give the transducers time to settle before the
echo returns to the receiver. The size of the blanking area is user selectable in the
software using the Start of profile parameter.
Bottom Track Bottom tracking is a method where the velocity of the bottom is measured. The
bottom track algorithm is a "single mode" and functions from the minimum depth to
the maximum depth, seamlessly.
Break A break command is used to change between the various operational modes of the
instrument and to interrupt the instrument regardless of which mode it is in. When
break is received in command mode, you can see that the LED is switched off for a
short time.
Broadband In this context it means using a more complex transmit pulse to improve the
measurement accuracy in each ping.
Cell (*) One measurement cell represents the average of the return signal for a given period.
The cell size and transmit pulse are of equal size.
Command
mode An instrument in command mode is powered up and ready to accept your
instructions. If no commands are received for about five minutes, it automatically
goes into Power Down Mode, unless Ethernet power is connected. LED is lit
constantly when in command mode.
Connector
Lubricant For example 3M Silicone Spray. Do not use grease.
Correlation (*) Nominal correlation is a function of cell size and velocity range. Nortek recommends
using 50% of the max correlation as a cut-off value, beyond this point the validity of
your data is questionable.
Desiccant Bag Added in the canister to absorb humidity
Firmware Internal software of the instrument, as opposed to the instrument software running on
a PC. Availability of new firmware versions is shown on the instrument web interface.
FOM (Figure
of Merit) Measure of the velocity white noise level (single ping precision).
Internal
sampling rate Rate of sampling for internal sensors. Refer to the specific instrument brochure for
details.
LED Light Emitting Diode.
License Different capabilities of the instrument are protected under licenses which can be
purchased. Contact your sales representative for more information. You will not need
a license when updating the firmware version.
MIDAS Nortek Multi-Instrument Data Acquisition Software
NMEA Standard data format defined by the National Marine Electronics Association
Noise floor The amplitude of the internal noise of the instrument. This will limit the minimum
detectable signal that can be received.
O-ring
lubricant Lubricate the O-rings with silicone grease. Properly greased O-rings will help
maintain sealing integrity and minimize O-ring degradation.
.pd0 Data format defined by RDI, that has been available for a long time. Format is
described in RDI Workhorse manual.
Ping Same as a single transmit pulse.
Precision (*) The value given is a theoretical estimate of the precision of the velocity
measurements based on how the instrument is set up. The nominal value is given for
the horizontal components in a default instrument acoustic beam configuration. In
order to improve the precision the user may consider one of the following options: (1)
larger cell sizes or (2) reduced velocity range
Pressure
Offset Due to atmospheric pressure variations, the sensor signal may have an offset. Note
that the sensor does not output negative values. Set the offset before deployment.
Sidelobe The acoustic beams focus most of the energy in the center of the beams, but a small
amount leaks out in other directions. Transducer sidelobes are rays of acoustic
energy that go in directions other than the main lobe. Because sound reflects
stronger from the water surface than it does from the water, the small signals that
travel straight to the surface can produce sufficient echo to contaminate the signal
from the water.
Signal
strength Strength of return signal, presented in dB.
SNR SNR is the Signal-to-Noise ratio and is a data quality indicator.