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Instruction Manual
IM-106-910C, Rev. 1.0
November 2009
System Description
The Hazardous Area X-STREAM O
net concentration of oxygen in an industrial combustion process; i.e., the
oxygen remaining after all fuels have been burned. The probe utilizes an "in
situ" zirconium oxide sensor placed on the end of a permanently mounted
probe that is positioned within an exhaust duct or stack. There is no sampling
system required.
The equipment measures oxygen percentage by reading the voltage
developed across a heated electrochemical cell, which consists of a small
yttria stabilized, zirconia disc. Both sides of the disc are coated with porous
metal electrodes. When operated at an elevated temperature the millivolt
output voltage of the cell is given by the following Nernst equation:
EMF = KT log10(P1/P2) + C
Where:
1. P2 is the partial pressure of the oxygen in the measured gas on one
side of the cell.
2. P1 is the partial pressure of the oxygen in the reference air on the
opposite side of the cell.
3. T is the absolute temperature.
4. C is the cell constant.
5. K is an arithmetic constant.
NOTE
Clean, dry, instrument air (20.95% oxygen) is required as reference air.
When the cell is at operating temperature and there are unequal oxygen
concentrations across the cell, oxygen ions will travel from the high oxygen
partial pressure side to the low oxygen partial pressure side of the cell. The
resulting logarithmic output voltage is approximately 50 mV per decade. The
output is proportional to the inverse logarithm of the oxygen concentration.
Therefore, the output signal increases as the oxygen concentration of the
sample gas decreases. This characteristic enables the Hazardous Area
X-STREAM O
Transmitter to provide exceptional sensitivity at low oxygen
2
concentrations found in combustion flue gases.
NOTE
Since the sensing cell is heated, and utilizes platinum electrodes that have
catalyzing properties, the Hazardous Area X-STREAM O
burn any residual fuel remaining in the flue gases from incomplete
combustion components (usually CO). This secondary combustion at the
sensing cell will consume a portion of any remaining oxygen (2CO + O
2CO
), and measures the net oxygen remaining after this secondary
2
combustion inside the cell occurs.
If your combustion process contains significant CO, or other residual fuel
components, the Oxygen reading may be depressed, or read zero.
Hazardous Area
X-STREAM O
Transmitter is designed to measure the
2
Transmitter
2
Transmitter cell will
2
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2
1-3
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