Filter
Top Products
Model 9110TH NOx Analyzer Calibration Procedures
Teledyne Analytical Instruments 195
9.1.2. CALIBRATION GASES
9.1.2.1. Zero Air
Zero air or zero calibration gas is defined as a gas that is similar in chemical composition to the
measured medium but without the gas to be measured by the analyzer.
For the 9110T, this means zero air should be devoid of NO, NO
2
, CO
2
, NH
3
or H
2
O vapor.
Note Moderate amounts of NH3 and H2O can be removed from the sample gas
stream by installing the optional sample gas dryer/scrubber (see Section
3.3.2.6).
If your application is not a measurement in ambient air, the zero calibration gas should be matched
to the composition of the gas being measured.
Pure nitrogen (N
2
) could be used as a zero gas for applications where NO
X
is measured in nitrogen.
If your analyzer is equipped with an external zero air scrubber option, it is capable of creating zero
air from ambient air.
For analyzers without the external zero air scrubber, a zero air generator such as the Teledyne Model 701
can be used. Please visit the company website for more information.
If your analyzer is equipped with an external zero air scrubber option, it is capable of creating zero air
from ambient air.
If your application is not a measurement in ambient air, the zero calibration gas should be matched
to the composition of the gas being measured.
Pure nitrogen could be used as a zero gas for applications where NO
X
is measured in nitrogen.
9.1.2.2. Span Gas
Calibration gas is a gas specifically mixed to match the chemical composition of the type of gas being
measured at near full scale of the desired reporting range. To measure NO
X
with the 9110T NO
X
analyzer, it is recommended that you use a span gas with an NO
concentration equal to 80% of the
measurement range for your application
EXAMPLE:
If the application is to measure NOX in ambient air between 0 ppm and 500 ppb, an appropriate
span gas would be 400 ppb.
If the application is to measure NOX in ambient air between 0 ppm and 1000 ppb, an appropriate
span gas would be 800 ppb.
We strongly recommend that span calibration be carried out with NO span gas. Alternatively it is
possible to use NO
2
gas in a gas phase titration (GPT) calibration system (see Section 10.5).
Even though NO gas mixed into in nitrogen gas (N
2
) could be used as a span gas, the matrix of the
balance gas is different and may cause interference problems or yield incorrect calibrations.