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NORTEK
13 Glossary
Accuracy
A value giving the degree of closeness of a velocity measurement to the
actual velocity. Refer to the data sheet for specific minimum accuracy.
AD2CP
Nortek's broadband signal processing platform.
AHRS
Attitude and Heading Reference System. Provide attitude information and
replace the traditional tilt and magnetometer. AHRS is especially useful in
dynamic environments. Note that this feature also requires additional
hardware.
Altimeter
Measures the distance to the surface
Amplitude
See signal strength
ASCII output
Data is displayed in ASCII format (plain text).
Bandwidth
Wider signal bandwidth is used to get more information and improve the
velocity precision. Reduced bandwidth is used in long range mode (only
relevant when current profiling) to increase range. This bandwidth reduction
makes the measurements less precise.
Beam
Coordinates
In Beam coordinates, a positive velocity is directed in the same direction as
the beam points. Beam 1 is marked with an “X” on the head.
Blanking
Specifies the distance from instrument head to the start of the measurement
cell 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.
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. The cell is shaped
like a triangle due to convolution; this is indicative of the weighting of the
measurement.
Coarse Profile
Instrument setup that prioritizes achieving the maximum range at the expense
of reduced resolution.
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.
Compass
calibration
Each compass system has been calibrated at the factory to quantify the
characteristic response of the individual components and of the system as a
whole. When it leaves the factory, each system can measure its tilt and the
direction of its magnetic field vector accurately. However, users may disturb
the magnetic field near the instrument when they deploy. Adding a battery
pack and mounting the instrument with deployment hardware adds magnetic
materials that change the earth's field at the instrument. The compass
calibration procedure quantifies this magnetic hard iron disturbance, and the
instrument's compass algorithm then corrects for it to obtain accurate
heading.
Correlation
(nominal)
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.
ENU
Coordinates
Polar magnetic coordinates; East, North and Up. A positive east velocity goes
toward east. This is a right-handed orthogonal system.
