Method of measuring the dew point or frost point of a gas having low water content

摘要

A method of determining the dew point or frost point of a gas containing a very small amount of water uses an optical dew point meter having a reflector mirror the temperature of which can be varied from room temperature to any point of -80° C. or below, a device for contacting the reflector mirror with the gas to be measured, a light source for irradiating the reflector mirror with focused rays of light, and a detector for detecting the change in scattered light and/or reflected light due to the dew and/or frost condensed on the reflector mirror. The method gradually reduces the temperature of the reflector mirror, either before or while the reflector mirror and the gas contact, thereby condensing dew and/or frost on the reflector mirror. Following formation of dew and/or frost on the reflector mirror, the intensity of scattered light or reflected light is adjusted from a maximum value to a constant level, at a controlled temperature. The temperature at that constant level of light intensity is determined as the dew or frost point.