A fast‐response oxygen sensor for use on fine‐scale and microstructure CTD profilers

A specialized oxygen sensor is described whose fast response times make it ideal for studies of the effects of mixing processes on oxygen concentrations. A polarographic oxygen microelectrode was installed on a microstructure CTD profiler. The oxygen microelectrode has a tip size of 30 µm, a total length of 5 cm, membrane thickness of <4 µm, and a time constant of 0.13 s. Flow dependence is minimal, and the amplifying and conditioning electronics are installed inside the body of the profiler, which is 50 cm long and 10 cm in diameter. The profiler samples temperature, gradient temperature, conductivity, dissolved oxygen, and pressure as it ascends through the water column at 10 cm s−1. Sampling at 100 Hz allows temperature, conductivity, and depth measurements every 1 mm and dissolved oxygen measurements every 1.3 cm.