Emerson Rosemount X-Stream Series, Инструкция по эксплуатации

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Emerson Process Management GmbH & Co. OHG
3-15
X-STREAM XE
Instruction Manual
HASXEE-IM-HS
10/2012
3
Measuring Principles
3.4 Trace Moisture Measurement
Fig. 3-14: Trace Moisture Sensor Assembly
1 Sensor
2 Sensor block
3 Gas connections
3.4 Trace Moisture Measurement
1
2
3
The Trace Mois
ture sensor is a robust
2-wire-transmitter, using dew point impe-
dance measurement for continuous moisture
measurements in gases and gas mixtures.
It makes dew point measurement as ac-
cessible as temperature and pressure.
Some definitions:
The dew point is the temperature in Deg C
to which a given parcel of humid air must be
cooled, at constant barometric pressure, for
water vapor to condense into water. The con-
densed water is called dew. The dew point is
the saturation temperature.
The dew point is associated with
relative
humidity. A high relative humidity indicates
that the dew point is closer to the current air
temperature. Relative humidity of 100 % in-
dicates the dew point is equal to the current
temperature and the air is maximally saturated
with water. If the dew point remains constant
and temperature increases, relative humidity
will decrease.
Humidity is the amount of water vapor in the
air. Relative humidity is defined as the ratio
of the partial pressure of water vapor (in a
gaseous mixture of air and water vapor) to
the saturated vapor pressure of water at a
given temperature.
This type of sensor is used, if dew point
measurements are required.