Yokogawa Integral Oxygen Analyzer ZR202 - Manual (Page 119)

IM 11M12A01-05E 9-2
Sample gas
Comparison
water vapor
1
2
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 r kg/kg, then “r” can be calculated from the value of
H
2
O vol% as follows:
r = 0.622 3 x/(100 – x) …………… Equation (4)
From the above equations (1), (2) and (4), we obtain:
E = -K log y/a = -K log {0.622 3 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 r kg/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