Arrangement for measuring the water vapor dew point in gases

US4898476A · kind A · utility

Assignee

• Endress u Hauser GmbH u Co. · DE

Inventors

• Rainer Herrmann · Hamburg, DE
• Dieter Funken · Lörrach, DE

Key dates

• Filing date: Aug 25, 1988
• Grant date: Feb 6, 1990
• Expiry date: Aug 25, 2008

Classification

• Technology area (CPC G): Physics
• CPC primary: G01N25/68
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

For measuring the water vapor dew point in gases, a moisture-dependent electrical quantity of a sensor surface suitable for indicating formation of dew droplets is held by temperature control at a desired value corresponding to a stable dew mass. The temperature of the sensor surface corresponding to the desired value of the moisture-dependent electrical quantity is measured as dew point temperature. For compensating the influence of soiling, from time to time the desired value of the moisture-dependent electrical quantity is set in that the temperature of the sensor surface is lowered from a value lying above the dew point temperature and a periodic time temperature variation superimposed on the lowering. If the sensor surface is soiled, periodic time variations of the moisture-dependent electrical quantity occur at the same time but they become a monotonic variation when the dew point temperature is reached. The value of the moisture-dependent electrical quantity measured on the transition of the periodic time variations to a monotonic variation is then used as the reference or desired value which is maintained by the control of the temperature of the sensor surface. Furthermore,…