Trace Oxygen Analyzer Operation
Teledyne Analytical Instruments 43
This preference is stored in non-volatile memory, so this
configuration is remembered after a power shutdown. If the instrument
is cold started, it will go back to default (not showing negative oxygen
readings).
4.4 The Zero and Span Functions Note: Zeroing is not required in order 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 as long as 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 ppm), the cell can take a long time to recover if the
instrument is used for trace oxygen analysis immediately following
calibration in air.
Connect the calibration gases according to the instructions given in
Section 3.4.1, 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 analyzer’s SLPM flowmeter) settles between 0.15 and 2.4
SLPM (approximately 0.2 - 5 SCFH).
If you are using password protection, you will need to enter your
password to gain access to either of these functions. Follow the
instructions in Sections 4.3.3 to enter your password. Once you have
gained clearance to proceed, you can enter the Zero or Span function.