1982 Volume 17 Issue 4 Pages 243-251
Reduced pressure tests were conducted in an pressure chamber. The purpose of these tests was to determine the characteristic behavior of the chemiluminescent ozone analyzer, UV absorption ozone analyzer and chemiluminescent nitrogen oxides analyzer to changing altitude, as in an unpressurized aircraft.
The instruments were placed in the chamber and calibrated at 1 atm. The chamber was then sealed and partially evacuated. Tests were run over the range of pressures corresponding to ground level to an altitude of approximately 2000 meters above sea level.
The results obtained were as follows:
1) The read out values of the chemiluminescent and UV absorption ozone analyzers decreased by approximately 22% at 0.78 atm (≅2000 meters above sea level), and the decreasing rate of the read out values was nearly equal to that of ambient pressure.
2) The read out values of the chemiluminescent NO, NOx analyzers decreased by 0-12% at 0.78 atm. The decreasing rate of the read out values was smaller than that of ambient pressure, and differed in each analyzer.
3) The influence of ambient pressure on ozone analyzers is principally due to the change of the mass flow rate of the sample air (in the case of chemiluminescent method), or due to the change of the mass concentration of ozone in absorption cell (in the case of UV absorption method).
4) The influence of ambient pressure on chemiluminescent NO, NOx analyzers is due to the change of the mass flow rate of the sample air and the change of response per unit mass flow rate.
