Ametek Thermox 2000 ATEX Series User Manual page 13

Figure 1-1.
Zirconium oxide cell
principle of operation.
where R and F are constants, T is absolute temperature, and O
the oxygen partial pressures on either side of the cell.
For measuring oxygen in non-combustibles gases, the calibration of an ana-
lyzer is obtained from the formula:
E = A T Log
* *
Where A is a constant, T is the cell temperature on an absolute scale (°C +
273) and O Unk% is the unknown oxygen concentration of the gas to be
2
analyzed, and which is calculated by the analyzer.
The cell produces zero voltage when the same amount of oxygen is on
both sides, and the voltage increases as the oxygen concentration of the
sample decreases. The voltage created by the difference in the sample gas
and the reference air is carried by a cable to the microprocessor control
unit, where it is linearized to an output signal.
Because of the high operating temperature of the cell, combustible
gases that are present may burn. When this occurs, the cell will gen-
NOTE
erate high millivolts and cause the display to indicate less oxygen
than is actually in the gas (net oxygen content).
20.9%
O Unk%
2
and O
1
AT = 48.0 at 695°C
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