Yokogawa Single Channel Oxygen Analyzer System ZR22/ZR402 User Manual
Page 138
IM 11M12A01-03E
9-2
Sample gas
Comparison
water vapor
ϩ
Ϫ
H
2
O
concentration
indicator
Electrode
Water vapor
100%
Air
100%
100%
H
2
O
79%
21%
O
2
N
2
y%
x%
Sample-gas composition
Zirconia element
F9.1.EPS
Figure 9.1 Schematic Diagram of Measurement Principle
(B) For the “mixing ratio” measurement
Assuming that the mixing ratio is rkg/kg, then “r” can be calculated from the value of
H
2
O vol % as follows:
r = 0.622
ϫ x/(100 – x) …………… Equation (4)
From the above equations (1), (2) and (4), we obtain:
E = -K log y/a = -K log
Ά0.622 ϫ 21/(0.622 + r)/21·
= -K log 0.622/(0.622 + r) … …… Equation (5)
where, K = Constant
With Equation (5), we can obtain the mixing ratio rkg/kg from the electromotive force.
120
100
80
60
40
20
0
0.1
1
10
100
Cell output, mV
E = -50.74*log PX/20.6
Oxygen concentration vs. cell output
Oxygen concentration PX (%O
2
)
FAE.EPS