YOKOGAWA EXAxt ZR402G, User Manual

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<10. Other Functions>
10-4
IM 11M12A01-04E 11th Edition : Jul. 19, 2017-00
10.1.11 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 750°C., may be expressed mathematically by:
E = -50.74 log (Px/Pa) [mV]
where, Px: Oxygen concentration in the sample gas
Pa: Oxygen concentration in the reference gas, (21 vol%O
2
)
Table 10.2 shows oxygen concentration versus cell voltage.
Table 10.2 Oxygen Concentration Vs. Cell Voltage, (cell temperature: 750°C)
%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.ai
10.1.12 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.
10.1.13 Cold Junction Voltage
This equipment uses temperature-measurement ICs that measure the cold junction
temperatures. The voltage measured by those ICs is displayed.
10.1.14 Current Output
The analog output current is displayed.
10.1.15 Response Time
The cell’s response time is obtained in the procedure shown in Figure 10.1. If only either zero or
span calibration has been carried out, the response time will not be measured just as it will not be
measured in manual calibration.