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13. A High Precision, Fast Response, and Low Power Consumption in Situ Optical Fiber Chemical pCO2 Sensor

Author

Lu, Zhongming, Dai, Minhan, Xu, Kunming, Chen, Jinshun, Liao, Yinhao, Lu, Zhongming, Dai, Minhan, Xu, Kunming, Chen, Jinshun, and Liao, Yinhao

Abstract

A sensor system suitable for monitoring changes in partial pressure of carbon dioxide (pCO2) in surface seawater or in the atmosphere has been developed. Surface seawater samples are pumped into a PVC tube enclosing an inner Teflon AF tube, which served as a long pathlength gas-permeable liquid-core waveguide for spectrophotometry. The Teflon cell contains a pH-sensitive indicator-buffer solution consisting of bromothymol blue (BTB) and sodium carbonate. Carbon dioxide in the sample diffuses into the indicator-buffer solution to reach equilibrium, resulting in pH changes, which are detected by changes in the absorbance of BTB at wavelengths of 620 and 434 nm. The pCO2 in the sample is then derived from the pH change. The sensor has a response time of 2 min at the 95% equilibrium value and a measurement precision of 0.26-0.37% in the range 200-800 μatm pCO2. This chemical sensor takes advantage of a combination of long pathlength, multiple wavelength detection, indicator solution renewal, and in situ automatic control technology, and has the feature of low power consumption (the average being ∼4 W with a peak of ∼8 W). © 2008 Elsevier B.V. All rights reserved.

Published
2008

14. Development and Application of an in Situ Optical Fiber Chemical CO2 Sensor

Author

Lu, Zhongming, Dai, Minhan, Chen, Jinshun, Xu, Kunming, Liao, Yinhao, Lu, Zhongming, Dai, Minhan, Chen, Jinshun, Xu, Kunming, and Liao, Yinhao

Abstract

An autonomous fiber optical chemical pCO2 sensor suitable for long-term in situ time series observations of seawater pCO2 is described. The sensor is based on a long pathlength gas- permeable liquid-core waveguide and pH sensitive indicator-buffer solution. The design combines a multi- wavelength low power consumption optical component, a miniature indicator and sample pump, a customized control and memory circuit to achieve long-term in-situ operation. The sensor makes a measurement every 3 min and achieves an optimal precision of 1 µatm for pCO2 in the range of 200-800 μatm and a response time (95%) of 2 min. The performance of the sensor was tested in lab through an inter-comparison with an infrared CO2 analyzer, and the results of a continuous experiment in the course of nearly a month showed a fairly stable response from sensor. The sensor was then tested in the field on a mooring system deployed at Taiwan Strait and subsequently applied in a time series observation in the South China Sea.

Published
2006

15. A high precision, fast response, and low power consumption in situ optical fiber chemical pCO2 sensor

Author

Lu, Zhongming, Dai, Minhan, Xu, Kunming, Chen, Jinshun, and Liao, Yinhao

Subjects
*CARBON dioxide, *POLYVINYL chloride, *SPECTROPHOTOMETRY, *CHEMICAL detectors
Abstract

Abstract: A sensor system suitable for monitoring changes in partial pressure of carbon dioxide (pCO2) in surface seawater or in the atmosphere has been developed. Surface seawater samples are pumped into a PVC tube enclosing an inner Teflon AF tube, which served as a long pathlength gas-permeable liquid-core waveguide for spectrophotometry. The Teflon cell contains a pH-sensitive indicator-buffer solution consisting of bromothymol blue (BTB) and sodium carbonate. Carbon dioxide in the sample diffuses into the indicator-buffer solution to reach equilibrium, resulting in pH changes, which are detected by changes in the absorbance of BTB at wavelengths of 620 and 434nm. The pCO2 in the sample is then derived from the pH change. The sensor has a response time of 2min at the 95% equilibrium value and a measurement precision of 0.26–0.37% in the range 200–800μatm pCO2. This chemical sensor takes advantage of a combination of long pathlength, multiple wavelength detection, indicator solution renewal, and in situ automatic control technology, and has the feature of low power consumption (the average being ∼4W with a peak of ∼8W). [Copyright &y& Elsevier]

Published
2008
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16. A high precision, fast response, and low power consumption in situ optical fiber chemical pCO2 sensor.

Author

Lu Z, Dai M, Xu K, Chen J, and Liao Y

Subjects
Air analysis, Hydrogen-Ion Concentration, Optical Fibers, Partial Pressure, Reproducibility of Results, Seawater chemistry, Spectrum Analysis, Carbon Dioxide analysis, Fiber Optic Technology methods
Abstract

A sensor system suitable for monitoring changes in partial pressure of carbon dioxide (pCO(2)) in surface seawater or in the atmosphere has been developed. Surface seawater samples are pumped into a PVC tube enclosing an inner Teflon AF tube, which served as a long pathlength gas-permeable liquid-core waveguide for spectrophotometry. The Teflon cell contains a pH-sensitive indicator-buffer solution consisting of bromothymol blue (BTB) and sodium carbonate. Carbon dioxide in the sample diffuses into the indicator-buffer solution to reach equilibrium, resulting in pH changes, which are detected by changes in the absorbance of BTB at wavelengths of 620 and 434 nm. The pCO(2) in the sample is then derived from the pH change. The sensor has a response time of 2 min at the 95% equilibrium value and a measurement precision of 0.26-0.37% in the range 200-800 microatm pCO(2). This chemical sensor takes advantage of a combination of long pathlength, multiple wavelength detection, indicator solution renewal, and in situ automatic control technology, and has the feature of low power consumption (the average being approximately 4 W with a peak of approximately 8 W).

Published
2008
Full Text
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