Ocean sensors - for marine environmental monitoring

Various sensors and instruments were developed to measure the chemical and physical properties of sea water, but many are expensive and too large to be used on mass deployed vehicles such as the Argo float and submersed gliders. Marine mammal and fish tags require further sensor miniaturisation. This thesis describes the development of new in-situ micro sensor technology for marine environmental monitoring.<br/><br/>Nitrite and nitrate are two forms of dissolved inorganic nitrogen in sea water and their availability is a key factor in the regulation of primary productivity in the sea. The in-situ determination of nitrite and nitrate in sea water presents a significant analytical challenge. In this thesis, a simple, low cost double beam spectrophotometer for use in a nitrite sensor for sea water analysis is presented. The sensor uses a colorimetric method to determinate nitrite concentration in sea water, based on Greiss reaction that forms as Azo dye whose absorbance is measured at a wave length of 540nm. The design incorporates a green LED and integrated photo-detectors to make the nitrite sensor compact, with low-cost and low-power consumption.<br/><br/>A Conductivity, Temperature, Depth (CTD) sensor is the primary tool for determining the physical properties of sea water. A new CT (Conductivity and Temperature) micro sensor is presented in this thesis. The temperature sensor uses a thermistor, and the conductivity sensor uses a novel design of four planar electrodes built in an insulated channel. Conductivity sensors built of planar electrodes can be easily mass-produced on PCB boards, thus significantly reducing cost.<br/><br/>This thesis includes the background of the measurement of conductivity, temperature and nitrite concentration in sea water. It also presents a comprehensive analysis of conductivity cells with two, four and five electrodes, together with the detailed multi-sensor interface design. The design and construction of the prototype sensors are described in detail, the key issues and test results are also presented.

Name dc:type.qualificationname

Ph.D.

Level dc:type.qualificationlevel

doctoral

Grantor dc:publisher.institution

University of Southampton

Year dc:date.issued

2010

Author dc:creator

• Gong, Weidong

Advisors dc:contributor.advisor

• Morgan, Hywel
• Kraft, Michael