A new simple pCO2 sensor with compact drifting buoy system for long term observation JAPANESE
Introduction Plan for development of CO2 sensor Theory CO2 sensor Anti-biofouling Data Observation systems
CO2 sensor
Drifting buoy with CO2 sensor 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.
Plate 1
Drifting buoy with CO2 sensor. The scale length is 300 mm.
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The components of CO2 sensor
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).
Plate 2
Interior of CO2 sensor
Plate 3
Sensor parts of CO2 sensor (Buoy bottom)
Plate 4
Spectrophotometer
Plate 5
Micro pump
Plate 6
Temperature and salinity sensor
Plate 7
Power save CPU board and Power board
Plate 8
LED light source
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Satellite communication system 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).
Plate 9
Flat antenna and transmitter for argos system
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