Dew-point measurements at high water vapour pressure

A dew-point meter capable of measuring humidity at high vapour pressure and high temperature has been constructed and tested. Humidity measurements in pure steam were made over the temperature range 100-150 degrees C and a vapour pressure range of 1-4 bar. The dew-point meter performance was assessed by comparing measurements with a pressure transmitter and agreement between the two was within +/-2.5% relative humidity. Humidity measurements in steam-air mixtures were also made and the dew-point meter readings were compared to those of a zirconia oxygen sensor. for these tests the dew-point meter readings were generally within +/-2.5% relative humidity of the oxygen sensor measurements.