Miniature Sensor Probe for O2, CO2, and H2O Monitoring in Portable Life Support Systems

摘要

A miniature sensor probe, comprised of four sensors that monitor the partial pressure of O2, CO2, H2O, and temperature, designed to operate in the portable life support system (PLSS), has been demonstrated. The probe provides an important advantage over existing technology in that it is able to operate reliably while wet. These luminescence-based fiber optic sensors consist of an indicator chemistry immobilized in a polymeric film, whose emission lifetime undergoes a strong change upon a reversible interaction with the target gas. Each sensor includes chemistry specifically sensitive to one target parameter. All four sensors are based on indicator chemistries that include luminescent dyes from the same chemical family and therefore exhibit similar photochemical properties, which allow measurements of all the sensors to be performed by a single, compact, low-power optoelectronic unit remotely connected to the sensors by an electromagnetic interference-proof optical fiber cable. For space systems, the ability to use these miniature sensor elements with remote optoelectronics provides unmatched design flexibility for measurements in highly constrained volume systems such as the PLSS. A prototype multiparameter probe 10 mm in diameter and 15 mm in length was designed, fabricated, tested, and demonstrated over a wide operational range of gas concentrations, humidity, and temperature relevant to operation in the PLSS. The sensors were evaluated for measurement range, precision, accuracy, and response time in temperatures ranging from 10°C to 65.5°C (50°F to 150°F) and relative humidity from dry to 100% RH. Operation of the sensors in water condensation conditions was demonstrated wherein the sensors not only tolerated liquid water, but actually operated while wet.