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The new simple system
is attached in aluminum drifting buoy with satellite communication
system, which size is about 300 mm diameter and 450 mm
length and weight is about 15 kg. A Li-ion battery for
1 year measurement is occupied about one third of the drifting
buoy. |
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Plate 1
Drifting buoy with CO2 sensor. The scale length is 300 mm. |
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| This measuring system was
constructed from CCD detector, micro pump, TS sensor
(Plate6), LED light source, optical fiber, downsized
PC (Plate7) and beam selector (Plate2,3). We adopted
USB 4000 (Ocean Optics, Inc.) as a spectrophotometer.
The USB 4000 is small size (89.1 x 63.3 x 34.4 mm),
responsive from 350nm to 800nm and features a 16-bit
A/D resolution. This interfaces to a CPU board via
RS-232 serial port (Plate4). The diaphragm micro pump
SDMP 302 (STAR MICRONICS CO., LTD.) features compact,
thin, lightweight (25_25 _ 4.8mm, 4g), self-priming,
long life (1.5 year on continuous driving), low power
consumption (Max: 0.1W ), and low electromagnetic noise.
Flow rate is controllable up to 3ml/min (Plate5). The
LED is suitable for autonomous buoy because low electrical
power. The pH indicator has maximum absorption wave
length at approximately 435nm and 600nm. To obtain
good precision and accuracy, we need flat intensity
from 435 to 700nm. However, general white LED has optical
intensity peaks at 470nm and 600nm and 470nm peak is
sharp. On the other hand, warm white LED has gentle
peaks and flat spectrum as compared with White LED
but the optical intensity is weak around 430nm. We
developed new LED light source by mixing blue, red
and white LED (Plate8). |
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Plate 2
Interior of CO2 sensor |
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Plate 3
Sensor parts of CO2 sensor (Buoy bottom) |
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Plate 4
Spectrophotometer |
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Plate 5
Micro pump |
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Plate 6
Temperature and salinity sensor |
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Plate 7
Power save CPU board and Power board |
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We adopted Argos
system for satellite communication. Considering running
cost, system size and cover area, Argos system is suitable
for the pCO2 sensor. This system has a small and power
save transmitter and flat antenna (usable for two-way communication
Argos 3, Plate 9). |
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Plate 9
Flat antenna and transmitter for argos system |
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