Abstract
Autonomous systems in the open ocean for a long-term observation need components that consume low power. We have been developing a compact drifting buoy system for pCO2 measurement. The measurement principle for the pCO2 sensor is based on spectrophotometry. The pCO2 is calculated from the absorbance of the pH indicator in the solution that is in equilibrium with respect to CO2 exchange between seawater sample. In general, Xenon lamp or tungsten halogen lamp, which require large amount of power, have been widely used as a light source for a spectrometer. We developed a low power consumption (max: 1.0 W) light source for spectrometry within visible light range by using Light Emitting Diode (LED). The LED light source consists of seven LED lamps (435 nm, 490 nm, 500 nm, 592 nm, 609 nm, 750 nm, White) and output light flux to optical fiber. As the results of stability test and temperature dependency test, the LED light source was stable compared to conventional light sources.
