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Percent Oxygen Analyzer
4.8 The Zero and Span Functions
Note: Zeroing is not required to achieve the published accuracy
specification of this unit.
Zeroing will eliminate offset error contributed by sensor,
electronics, and internal and external sampling system and
improve performance beyond published specification limits.
The analyzer is calibrated using zero and span gases.
Any suitable oxygen-free gas can be used for zero gas provided it is
known to be oxygen free and does not react adversely with the sample
system.
Although the instrument can be spanned using air, a span gas with a
known oxygen concentration in the range of 70–90% of full scale of the
range of interest is recommended. Since the oxygen concentration in air
is 20.9% (209,000 %), the cell can take a long time to recover if the
instrument is used for percent oxygen analysis immediately following
calibration in air.
Connect the calibration gases according to the instructions given in
Section 3.3.1, Gas Connections, observing all the prescribed
precautions.
Shut off the gas pressure before connecting it to the analyzer
and be sure to limit the pressure to 40 psig or less when turning it
back on.
Readjust the gas pressure into the analyzer until the flowrate (as
read on the Main screen settles between 150 and 2400 SLPM (ap-
proximately 0.2 - 5 SCFH).
Teledyne Analytical Instruments
Operation
87
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