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Diffusion of oxygen into Teflon-type tubing over long distances.
•
•
PTFE or related materials can act as permeation devices. In fact, the permeable
membrane of NO
•
When using very long supply lines (> 1 m) between high concentration span
gases and the dilution system, oxygen from ambient air can diffuse into the line
and react with NO to form NO
•
•
DISCREPANCY BETWEEN ANALOG OUTPUT AND DISPLAY
If the concentration reported through the analog outputs does not agree with the value
reported on the front panel, you may need to recalibrate the analog outputs.
This becomes more likely when using a low concentration or low analog output range.
•
•
Analog outputs running at 0.1 V full scale should always be calibrated manually.
•
See Section 2.5.8.1 for a detailed description of this procedure.
DISCREPANCY BETWEEN NO AND NOX SLOPES
If the slopes for NO and NO
than 1%), consider the following three problems:
•
NO
impurities in the NO calibration gas. NO gases often exhibit NO
2
1-2% of the NO value.
This will cause differences in the calibration slopes. If the NO2 impurity in NO is
•
known, it can easily be accounted for by setting the expected values for NO and
NO2 accordingly to different values, e.g., 448 ppb NO and 450 ppb NOX.
•
This problem is worse if NO gas is stored in a cylinder with balance air instead of
balance gas nitrogen or large amounts of nitrous oxide (N2O), because the
oxygen in the air slowly reacts with NO to yield NO2, increasing over time.
•
The expected concentrations for NO and NO
different values.
•
If a gas with 100% pure NO is used, this would cause a bias.
•
See Section 4.2 on how to set expected concentration values.
An instrument calibration with the IZS option (and expected concentrations set to the same
amount) will always yield identical slopes for NO and NO
only NO
X
O
THER
Dynamic problems (i.e., problems that only manifest themselves when the analyzer is
monitoring sample gas) can be the most difficult and time consuming to isolate and resolve.
The following section provides an itemized list of the most common dynamic problems
with recommended troubleshooting checks and corrective actions.
083730200A DCN7962
permeation tubes is made of PTFE.
2
This reaction is dependent on NO concentration and accelerates with
increasing NO concentration, hence, affects linearity only at high NO levels.
Using stainless steel for long span gas supply lines avoids this problem.
are significantly different after software calibration (more
X
and assumes NO to be the same (with NO
P
P
ERFORMANCE
ROBLEMS
Teledyne API T200 NO/NO
.
2
in the calibration menu are set to
X
, as the instrument measures
X
being zero).
2
/NO
Analyzer with NumaView™ Software
2
x
on the order of
2
149
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Table of Contents
Troubleshooting
