Dew Point Transmitter
Al203 oxide sensors measure changes in partial water vapor pressure (PWVP). They follow complicated principles of physical chemistry. Henry’s Law defines the relationship between PWVP and water concentration in PPMW (μg /g).
Henry’s Law PPMW(μg /g)=PWVP * K
K is Henry’s constant. This constant is effected by sample matrix and temperature. COSA Xentaur has developed a sample system with an integral “Grab” sample to facilitate the determination of K in the “real” process. The sample system can then be used on a routine basis to validate K.
The procedure required to make a small number of empirical measurement is quite easy. By utilizing the “grab” sample, K is easily calculated. This is done at 2 critical concentrations. This data is then incorporated into a look-up table. The table is completed utilizing Henry’s Law theory. By using this approach PPMW (ug/g) measurements are possible directly from the sensor.
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