Yokogawa Integral Oxygen Analyzer ZR202 - Manual (Page 130)

IM 11M12A01-05E 10-3
10. Other Functions
10.1.1 Oxygen Concentration
The oxygen concentration in the process gas is displayed (consult Section 9.1.1, earlier
in this manual).
10.1.2 Humidity
The moisture content contained in air is displayed where the process gas contains water
vapors and air (refer to Section 9.1.1, earlier in this manual).
10.1.3 Mixing Ratio
Where the process gas contains water vapors and air, their mixing ratio is displayed
(refer to Section 9.1.1, earlier in this manual).
10.1.4 Relative Humidity
The relative humidity “U” may be obtained using the following theoretical equation (JIS
Z 8806).
U =
e
/
e
s
3100
where,
e
= Water vapor pressure of moist air
e
s
= Saturated water vapor
Since the gas-pressure ratio is equal to the volume ratio, the above equation may be
expressed mathematically by:
U = P 3H/
e
s
3100
where, P = Gas pressure
H = Humidity (volume ratio)
The saturated water vapor pressure e
s
is determined by a gas temperature, so the relative
humidity can be obtained by entering the parameters. Use parameter F13 for temperature
entry. Use parameter F14 for pressure entry.
10.1.5 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 and
volume ratio (= pressure ratio), as given below.
e = P 3 H
where, e = Water vapor pressure in moist air
P = Gas pressure
H = Humidity (volume ratio)
Use the above equation to find the water vapor in the moist air, and use the theoretical
equation (JIS Z 8806) to obtain the temperature at which that water vapor is equal to the
saturated water vapor pressure.