LABORATORY TESTS ON THE PERFORMANCE OF ALHMINIUM OXIDE. SILICON. AND OPTICAL. CHILLED MIRROR HYGROMETERS FOR LIGHT AND HEAVY WATER VAPOR DETERMINATIONS

摘要

Laboratory tests were carried out on the performance of aluminum oxide, silicon dioxide and optical chilled mirror condensation hygrometers for water vapor pressure(dew point) determinations. The silicon sensor was the fastest responding hygrometer while the condensation hygrometers were superior with respect to minimizing long term drift. If operation was under infrequent cycling conditions, the operational accuracy of the aluminum oxide sensor was inferior to that obtained during frequently cycling conditions and to the accuracies of the silicon and chilled mirror sensors. For operation with D_20, the Si sensor exhibited the expected 3 to 4℃ shift to lower readings due to the lower vapor pressures of D_2O as compared to H_20 at a given dew point temperature. Larger shifts were exhibited by the aluminum oxide sensor and an empirical calibration was required. Use of C0_2 instead of nitrogen background gas resulted in consistently lower readings by about 1° and 2℃ for the Si and aluminum oxide probes, respectively.