2:30 PM - 2:45 PM
△ [20p-A301-6] Development of the Active Dew-Point Control Systems for Improving the Accuracy of Generated Dew Points in the High Humidity Generator
Keywords:humidity, control, accuracy
Humidity standard, which is a gas with known humidity, is needed for calibrating and testing hygrometers used in many industrial fields such as automotive and meteorology. In this study, we developed active dew-point control systems for a primary humidity generator of high humidity in order to improve accuracy of generated dew points. Developing the active dew-point control system (DCS), we have already succeeded in suppressing dew-point falls in generating a gas with a high dew point and dew-point changes under pressure drifts in the test chamber caused by room-pressure changes. However, this system had trouble in suppressing dew-point oscillations under large temperature oscillations in the generator. To address this challenge, we developed the advanced DCS (ADCS), which increased the responsiveness of the generator-pressure control by using an additional pressure control method with the expansion valve. In the system, the actual vapor-liquid equilibrium temperature of water in the generator was estimated for the dew-point control. Using the ADCS, we were successful in improving the dew-point stability by more than 20-fold.