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A data cable
connects the computer to a combination leveling device and sensor
package that floats freely below the platform. A buoyancy compensation
unit within the leveler is used to move the sensor system up and
down the water column; the leveler can sample at user-specified
intervals to depths of 100 m with a precision of 0.2 m of a target
depth. The leveler is designed to accommodate standard water quality
sensor packages (e.g. Yellow
Springs Instruments© or Hydrolab©
sensors). The sensors transmit data via the communication cable
into a memory buffer within the on-board computer, where it can
be downloaded on demand via a combination modem/cell phone. RUSS
units are thus able to provide near real-time water quality data
at user-specified sampling intervals, virtually independent of lake
conditions.
For an up close image of a RUSS unit on Lake Minnetonka (with
our highly engineered and very effective bird deterrent system)
click here
The only effective
time limitations to sampling frequencies are the times required
for the sensor unit to descend to a specified depth and for the
individual sensors to equilibrate. In reality, the relevance of
the data is specific to the event being sampled; turbidity, temperature
and electrical conductivity might be relevant on a daily basis,
whereas oxygen profiles may change hourly. The appropriate sampling
interval depends, therefore, on the question being asked. The RUSS
units currently in place as part of the Water
on the Web and Lake Access projects have been
initially programmed to collect 1 m interval profiles at four and
six-hour intervals, respectively. The units are active 24 hours
a day, seven days per week, during open water and ice-on lake conditions;
units are only removed from the lake during freezing and thawing
conditions.
In addition to real-time data from the RUSS units, we provide up-to-date
information on weather conditions around the metro region.
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