6 cell temperature, 7 process gas temperature, 8 cold junction temperature – Yokogawa Integral Oxygen Analyzer ZR202 User Manual
Page 131: 9 cell voltage, 10 thermocouple voltage, 11 cold junction voltage
IM 11M12A01-05E
10-4
10.1.6 Cell Temperature
The cell temperature can be obtained from the thermoelectromotive force and cold
junction temperature; normally 7508C is displayed.
10.1.7 Process Gas Temperature
A process gas temperature set with parameter code F13 is displayed.
10.1.8 Cold Junction Temperature
This is the internal (where the electronics is installed) temperature of equipment, which
compensates for the cold junction temperature for a thermocouple measuring the cell
temperature. If this temperature exceeds 858C, the electronics may fail. If the internal
temperature exceeds this, take countermeasures to reduce the temperature such as by not
exposing the equipment to radiation.
10.1.9 Cell Voltage
The cell (sensor) voltage will be an index to determine the amount of degradation of the
sensor. The cell voltage corresponds to the oxygen concentration currently being
measured. If the indicated voltage approximates the ideal value (corresponding to the
measured oxygen concentration), the sensor will be assumed to be normal.
The ideal value of the cell voltage (E), when the oxygen concentration measurement
temperature is controlled at 7508C., may be expressed mathematically by:
E = -50.74 log (Px/Pa) [mV]
where, Px: Oxygen concentration in the process gas
Pa: Oxygen concentration in the reference gas, (21% O
2
)
Table 10.2 Oxygen Concentration Vs. Cell Voltage, (cell temperature: 7508C)
%O
2
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
mv 117.83
102.56
93.62
87.28
82.36
78.35
74.95
72.01
69.41
%O
2
1
2
3
4
5
6
7
8
9
mv
67.09
51.82
42.88
36.54
31.62
27.61
24.21
21.27
18.67
%O
2
10
21.0
30
40
50
60
70
80
90
mv
16.35
0
-7.86
-14.2
-19.2
-23.1
-26.5
-29.5
-32.1
%O
2
100
mv -34.4
T10.2E.EPS
10.1.10 Thermocouple Voltage
The cell temperature is measured with a Type K (chromel-alumel) thermocouple. The
thermocouple cold junction is located in the detector terminal box. The cell temperature
and the thermocouple voltage (including the voltage corresponding to the cold junction
temperature) are displayed.
10.1.11 Cold Junction Voltage
This equipment uses temperature-measurement ICs that measure the cold junction
temperatures. The voltage measured by those ICs is displayed.