4
O
PERATION
748213-P Rosemount Analytical June 1997
4-1
Model 755R Oxygen Analyzer
4.1 ROUTINE OPERATION
After the calibration procedure of Section 3.4, admit sample gas to the analyzer at the
same pressure and the same flow rates used for the zero and span gases. The
instrument will now continuously indicate the oxygen content of the sample gas.
4.2 EFFECT OF BAROMETRIC PRESSURE CHANGES ON
INSTRUMENT READOUT
If the analyzer exhaust port is vented through a suitable absolute backpressure
regulator, barometric pressure changes do not affect the percent oxygen readout.
However, if the analyzer exhaust port is vented directly to the atmosphere, any change
in barometric pressure after instrument standardization will result in a directly
proportional change in the indicated percentage of oxygen. This effect may be
compensated in various ways. If desired, correction may be made by the following
equation:
True % Oxygen = (P
st
/P
an
)(Indicated % Oxygen)
Where:
P
st
= Operating pressure during standardization
P
an
= Operating pressure sample analysis
Example: U.S. Units
P
st
= 760 mm Hg
P
an
= 740 mm Hg
Indicated % O
2
True % O
2
= (760/740)(40%) = 41.1% O
2
Example: S.I. Units
P
st
= 101 kPa
P
an
= 98.2 kPa
Indicated % O
2
= 40%
True % O
2
= (101/98.2)(40%) = 41.1% O
2
