Development of an underwater in-situ spectrophotometric sensor for seawater pH

Robert D. Waterbury; Robert H. Byrne; John Kelly; Bram Leader; Sean McElligott; Randy Russell

doi:10.1117/12.260590

10 December 1996 Development of an underwater in-situ spectrophotometric sensor for seawater pH

Robert D. Waterbury, Robert H. Byrne, John Kelly, Bram Leader, Sean McElligott, Randy Russell

Proceedings Volume 2836, Chemical, Biochemical, and Environmental Fiber Sensors VIII; (1996) https://doi.org/10.1117/12.260590
Event: SPIE's 1996 International Symposium on Optical Science, Engineering, and Instrumentation, 1996, Denver, CO, United States

Abstract

A pH sensor based upon spectrophotometric techniques has been developed for in-situ analysis of surface seawater. This sensor utilizes a spectrophotometric pH indicator (Thymol Blue) which has been calibrated for use in seawater as a function of temperature and salinity. Shipboard spectrophotometric pH analyses routinely demonstrate a precision on the order of plus or minus 0.0004 pH units. In- situ analysis of seawater pH has demonstrated a precision on the order of plus or minus 0.001 and an accuracy, using shipboard measurements as a standard, on the order of plus or minus 0.01. The sensor is a self-contained system which pumps seawater, meters in indicator, spectrophotometrically determines indicator absorbance and stores data with a 1 Hz acquisition frequency. The sensor employs two absorbance cells, each with three wavelength channels, to obtain the spectrophotometric absorbance. The sensor system, rated for depths up to 500 m, provides pH, conductivity, temperature and can be operated via computer or in a standalone mode with internal data storage. The sensor utilizes less than 12 watts of power and is packaged in a 29' long by 4.5' diameter aluminum housing.

Citation Download Citation

Robert D. Waterbury, Robert H. Byrne, John Kelly, Bram Leader, Sean McElligott, and Randy Russell "Development of an underwater in-situ spectrophotometric sensor for seawater pH", Proc. SPIE 2836, Chemical, Biochemical, and Environmental Fiber Sensors VIII, (10 December 1996); https://doi.org/10.1117/12.260590

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