Climatic Chamber for Dew-Point Temperatures Up to 150 °C

A traceable humidity generator for temperatures up to 180 °C and pressures up to 600 kPa was realized using simple techniques and with a chamber of a considerable volume (approximately 40 l). A relative humidity setup, used for calibrating sensors at temperatures up to 180 °C and dew-point temperatures up to 95 °C, was modified to allow for the generation of dew-point temperatures up to 150 °C, thus extending the maximum relative humidity at 180 °C from 8%rh to 45%rh. The uncertainty in the generated relative humidity remained 0.2%rh at 5%rh and increases to 0.4%rh at 95%rh. Seven industrial sensors of two different types and manufacturer (one capacitive sensor and one acoustic sensor) were tested in the setup. For both types the tests were used to obtain information about the behaviour of the sensors at high air and dew-point temperatures and high pressures. The capacitive sensors were tested up to 180 °C for determining their temperature and relative humidity correction function and the acoustic sensors were tested up to 120 °C for investigating the speed of sound.