September
2017
Sentinel V SC and RT Operation Manual
Page 60
EAR-Controlled Technology Subject to Restrictions Contained on the Cover Page.
based on the Sentinel V ADCP frequency, the water salinity, water temperature and the actual deployment
depth of the ADCP.
Cell size
– Sets the cell size. Adjust the cell size as necessary as recommended in Table 3. A larger cell size
decreases the standard deviation, but shallow water situations may need to use smaller cells to gather
more data points.
It is not recommended to set the cell size below the minimum or above the maximum range
shown in Table 3
Blank
– Moves the location of the first cell away from the Sentinel V ADCP transducer head to allow the
transmit circuits time to recover before the receive cycle begins. The default value is based on system fre-
quency and it is highly recommended to use this value. Setting a value below the default blank distance
may show ringing/recovery problems in the first depth cells.
It is not recommended to set the blank below the default value shown in Table 3.
Table 3.
Blank Distance, Range, and Cell Size
System
Blank Distance (Default)
Range (Default)
Cell Size (Default
(Min – Max))
Sentinel V 100m (307.2kHz)
1.6m
100m
4m
(1m - 6m)
Sentinel V 50m (491.52kHz)
1.0m
50m
2m
(0.6m - 4.8m)
Sentinel V 20m (983.04kHz)
0.4m
20m
1m
(0.3m - 2.4)
Number of cells
– Sets the number of depth cells. The value will be calculated based on the
Range
and
Cell
size
.
First Cell
– The range from the transducer face to the middle of the first cell. The
Cell size
and the
Blank
pri-
marily affect where it is located.
Number of pings
– Adjust the number of pings to gather the desired Standard Deviation. To increase the
expected accuracy of the velocity measurement (reduce the Standard Deviation), increase either the num-
ber of pings, cell size, or both.
Ping interval
– Sets the time per ping.
Ambiguity velocity
– Ambiguity velocity represents the maximum relative velocity (Sentinel V ADCP mo-
tion plus the maximum actual water velocity) the ADCP can measure along a beam. Select one of the set-
tings from the drop-down list. This must be set correctly to avoid ambiguity errors. Ambiguity velocity is
used to improve the standard deviation: The lower the value of the ambiguity velocity, the lower the sin-
gle-ping standard deviation.
Bandwidth
– Sets the profiling bandwidth and sampling rate. Smaller bandwidths allow the ADCP to pro-
file farther, but the standard deviation is increased by as much as 2.5 times.
Bandwidth
Sample rate
Standard deviation
Profiling range
High (25%)
High
Low
Low
Low (6.25%)
Low
High
High
Standard deviation – This shows the expected standard deviation of the velocity data stored in each
ensemble being collected by the Sentinel V ADCP. Most users will want to minimize this value so that they
obtain the best data possible (i.e. data containing the least amount of noise). Standard deviation is de-
pendent on cell size, the Number of pings, Ambiguity velocity, and the Bandwidth.
Enable vertical profile
– Check this box to enable the vertical beam profile.
