Yokogawa Single Channel Oxygen Analyzer System ZR22/ZR402 - Manual (Page 132)

IM 11M12A01-03E 8-20
8.6.3 Setting Measurement Gas Temperature and Pressure
The analyzer calculates the moisture content contained in exhaust gases and saturated
water vapors from the entered gas temperature and pressure to obtain the relative
humidity and dew point. The relative humidity may be obtained using the following
theoretical equation (JIS Z 8806).
To obtain the relative humidity:
The relative humidity U that is obtained from JIS Z 8806 is:
U = e/ e s ϫ 100
where, e = water vapor pressure of moist air
es = Saturated water vapor
Since the gas-pressure ratio is equal to the volume ratio, the above equation may be
expressed mathematically by:
U = P ϫ H/ e s ϫ 100
where, P = Gas pressure
H = moisture content (volume ratio)
The saturated water vapor pressure es is determined by a gas temperature, so the relative
humidity can be obtained by entering the above parameters.
To obtain the dew point:
The dew point is the temperature at which a water vapor pressure in the moist air is
equal to the saturated water vapor pressure.
The water vapor pressure in the moist air can be obtained from the gas pressure a-
d volume ratio (= pressure ratio), as given belo
.
where, e = water vapor pressure in moist a
P = gas pressu
H = Humidity (moisture content) (volume rati