DVL
20
© 2017 Nortek AS
Check out the
Nortek DVL Integrators Guide
for examples showing how to setup the instrument to
use a specific trigger.
When triggered the instrument will perform a complete ping (Tx and Rx) before it goes back to
monitoring the trigger. Any triggers asserted during an ongoing ping will be ignored. There are no
specific requirements for pulse length.
6.4
DVL Configuration
Trigger Mode
The trigger mode specifies what controls the acoustic pinging. This is either the
instrument and its internal timing mechanism (INTSR), trigger from a command (SERIAL) or a
hardware based trigger (TTL or RS485 input lines). For the hardware trigger there are three options:
rising edge, falling edge or both edges. The hardware triggers will be ignored if they occur at a faster
rate than what is possible to process for the configured range.
Sample Rate:
The data sampling rate (controlled by internal timers) used when INTSR is selected.
The sample rate is ignored for all other configured triggers. Note that the maximum range may be
reduced if a high sample rate is selected (the new limits will then be shown after you click submit).
Speed of Sound:
This is the speed at which sound travels through the water and is important for
estimating velocity in the Doppler processing. The user may select between "Measured" which is
estimated from the measured temperature, the measured pressure and the configured salinity or
"Fixed" which is a fixed value. End user using external estimates of speed of sound wishing to apply
the linear corrections outside of the DVL estimation process should use the fixed setting.
Salinity:
This is the estimated salinity (in parts per thousand) for the location the DVL will be
operating. The typical value is 35 ppt for sea water. Configuration of this value is only relevant if the
end user sets the speed of sound configuration to Measured.
Enable Data Recording
: Check this box if you wish to log data to the internal SD memory card.
Data Recording Filename:
This is the name of the file for the data recording file. If the same name
exists on the recorder then data is appended to the existing file. If the recorder gets full, the
measurement continues but data is no longer stored to the recorder.
Bottom Track
Blanking Distance:
This is the distance where the DVL begins to search for bottom. Check out the
section about false detects and blanking distance below.
Range:
This is the maximum distance at which bottom is detected (along the DVL's Z-axis). The
maximum range may be reduced if a high sample rate is selected (the new limits will then be shown
after you click submit). If the vehicle is to operate in an environment with multiple reflections (e.g.
shallow waters) it is recommended to set the range accordingly.
Transmit Power:
This is the amount of acoustic energy that is output from the DVL. Lower power is
sometimes desirable if there is an interest in reducing power consumption or if only a short profile
shall be measured. The maximum power level is range dependent, so the user may either let the
firmware select the maximum (MAX) given the current configuration or choose a value (USER). If
USER is selected, a power level of 0 dB represents maximum power output. In some configurations,
the maximum power is given as -2. Power is decreased by entering negative values.
Bottom Track Data:
This is the data output (and recording if selected) format for the DVL. The DF21
binary data format includes complete DVL data products, while variants of PD# are available for
platforms limited to this legacy format. A complete description is found in the DVL Integrators Guide.
Enable Water Track:
Check this box to enable velocity estimates relative to the water.
