title: Solid-state electrolyte sensors for rebreather applications: a preliminary investigation.
abstract: BACKGROUND
  Recently developed prototypes of zirconium dioxide and NASICON-based micro solid-state electrolyte oxygen (O2) and carbon dioxide (CO2) sensors were tested for their potential suitability in rebreathers. The O2 sensor has a quasi-indefinite lifetime, whilst that of the CO2 sensor is approximately 700 h. This is a preliminary report of a new technological application.
  
  
  METHODS
  The O2 sensor was tested in a small pressure chamber to a partial pressure of oxygen (PO2) of 405 kPa (4 bar). The CO2 sensor was tested up to 10 kPa CO2. The response times to a step change of pressure were measured, and cross-sensitivity for helium tested using trimix. A rebreather mouthpiece was modified so that breath-by-breath gas recordings could be observed. Power consumption to heat the sensors was measured.
  
  
  RESULTS
  The O2 sensor demonstrated non-linearity, particularly above 101.3 kPa (1 bar) PO2, whereas the output of the CO2 sensor showed an inverse logarithmic relationship. Cross-sensitivity to helium was observed. The mean t90 response times were 90 (SD 10) ms for the O2 sensor, and 100 (SD 10) ms for the CO2 sensor. Breath-by-breath recordings showed slight damping of the CO2 trace due to electronic filtering. Power consumption was 1.5-2 W per sensor.
  
  
  CONCLUSIONS
  The fast response times would allow accurate breath-by-breath measurement. Even though the O2 sensor has a non-linear response, measurement is possible using multi-point calibration. Further design is necessary to allow trimix to be used as the diluent. A major disadvantage is the high power consumption needed to heat the sensors to high temperatures.
authors.affiliation: IMEGO AB, Göteborg, Sweden. asieber@gmx.at
authors.forename: Arne
authors.initials: A
authors.lastname: Sieber
authors.forename: Rainer
authors.initials: R
authors.lastname: Baumann
authors.forename: Stefanos
authors.initials: S
authors.lastname: Fasoulas
authors.forename: Anatol
authors.initials: A
authors.lastname: Krozer
mesh_terms: D015374:Biosensing Techniques / Q000295:instrumentation* / Q000379:methods; D002245:Carbon Dioxide / Q000032:analysis*; D004242:Diving; D004867:Equipment Design; D006371:Helium / Q000032:analysis; D006801:Humans; D010100:Oxygen / Q000032:analysis*; D010313:Partial Pressure; D012119:Respiration; D013997:Time Factors
chemical_list: D002245:Carbon Dioxide; D006371:Helium; D010100:Oxygen