Development of a Helium/Carbon Dioxide/Hydrogen Sensor System for SCUBA.

摘要

The feasibility of a Helium/Carbon Dioxide/Hydrogen sensor system for SCUBA diving has been investigated. The helium sensor is a piezoelectrically excited diaphragm with its acoustic characteristics related to the helium concentration. The carbon dioxide sensor is an enzymatic/electrolyte anion exchange cell operating in a diffusion controlled mode, where the cell current is proportional to the partial pressure of CO2. The hydrogen sensor is a hydrogen/oxygen fuel cell operating in the hydrogen-diffusion-limited mode where the short circuit current is directly proportional to the hydrogen partial pressure. Laboratory versions of various sensors have been fabricated and tested. Helium sensors based on frequency shift were found to be ineffective, whereas those based on amplitude attenuation measurement were feasible but impractical due to its requirement for depth correction. A more attractive ultrasonic speed-of-sound sensor which circumvents this problem has evolved from the current development. Also, the feasibility and practicality of the CO2 and H2 sensors has been demonstrated. These sensors were found to be compact, rugged, sensitive, fast responding and linear within the range of interest.