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NDIR Gas Analyzer
CAUTION: The inlet gas pressure must be less than 5 psig. Do not exceed
5 psig. The sample cell is not designed to withstand
pressurization in excess of this. Make sure there are no kinks,
tight bends, or other obstructions in the sample system that
could generate excessive backpressure.
The standard models are equipped with an automatic calibration
feature which allows zero, span, or both calibrations to be performed
automatically. The user can also select the frequency of automatic
calibration. See Section 4.2 for details in setting up the instrument for
preprogrammed calibration events.
5.3
Manual Calibration
It is possible to manually calibrate the instrument at any time even if
an auto calibration period has been set. In order to obtain a valid
calibration, the sample cell must be purged of sample gas. This is
conveniently handled by having an appropriate CAL DELAY value
configured into the instrument via the SETUP function. See Section 4.2
SETUP Menu, for procedures involved in setting the CAL DELAY.
With an appropriate CAL DELAY set, make sure that the calibration
source pressure is the same as the sample gas pressure and less than 5
psig.
NOTE:
The pressure in the sample cell during calibration must be the same
as when flowing sample gas. Both the IR detector and the optional
oxygen sensor are sensitive to significant pressure or flow variations.
5.3.1 Manual Zero Calibration
A manual zero calibration involves:
1. Stopping the sample flow and switching to zero gas
2. Purging the sample cell with zero gas
3. Using the CALIBRATE?/ZERO submenu of the MODE menu
to request a manual zero calibration.
To manually zero calibrate the analyzer:
•
Referring to the flow diagram in Figure 5-1A, manually switch
the 3-way valve from sample gas to ZERO gas. Make sure that
valve B is set to flow gas in the position shown in the inset.
•
While watching the flowmeter, use the needle valve to adjust
the flow to 1.5 SCFH or to the same flowrate that is used for
sample gas.
Teledyne Analytical Instruments., - Rev. 3
Calibration 5
47
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