Teledyne 9110E - Nitrogen Oxides Analyzer - Manual (Page 128)

Calibration Procedures Model 9110E Instruction Manual
114 M9110E Rev B
We strongly recommend that span calibration is carried out with NO span gas, although it is
possible to use NO
2
or a gas phase titration (GPT) system. Quick span checks may be done
with either NO, NO
2
or a mixture of NO and NO
2
as is used in GPT. Span gases should be
certified to a specific accuracy to ensure accurate calibration of the analyzer. Typical gas
accuracy for NO
X
gases is 1 or 2%. NO standards should be mixed in nitrogen (to prevent
oxidation of NO to NO
2
over time), whereas NO
2
standards should be mixed in air (to keep
it oxidized).
7.1.4. NO
2
Permeation Tubes
TAI offers an internal zero / span (IZS) option operating with an NO
2
permeation device.
The accuracy of these devices is only about ±5%. Whereas this may be sufficient for quick,
daily calibration checks, we recommend to use certified NO gases for accurate calibration.
Note that US-EPA controlled applications do not allow permeation devices to be used for
calibration.
7.1.5. Calibration Gas Traceability
All equipment used to produce calibration gases should be verified against standards of the
National Institute for Standards and Technology (NIST). To ensure NIST traceability, we
recommend to acquire cylinders of working gas that are certified to be traceable to NIST
standard reference materials (SRM). These are available from a variety of commercial
sources.
7.1.6. Data Recording Devices
A strip chart recorder, data acquisition system or digital data acquisition system should be
used to record data from the serial or analog outputs of the M9110E. If analog readings are
used, the response of the recording system should be checked against a NIST traceable
voltage source or meter. Data recording devices should be capable of bi-polar operation so
that negative readings can be recorded. For electronic data recording, the M9110E provides
an internal data acquisition system (iDAS), which is described in detail in Section 6.9.10.
APICOM, a remote control program, is also provided as a convenient and powerful tool for
data handling, download, storage, quick check and plotting.
7.1.7. NO
2
Conversion Efficiency
To ensure accurate operation of the M9110E, it is important to check the NO
2
conversion
efficiency (CE) periodically and to update this value as necessary. The default setting for the
NO
2
converter efficiency is 1.0000. For the analyzer to function correctly, the converter
efficiency must be between 0.9600 and 1.0200 (96-102% conversion efficiency) as per US-
EPA requirements. If the converter’s efficiency is outside these limits, the NO
2
converter
should be replaced. The currently programmed CE is recorded along with the calibration
data in the iDAS for documentation and performance analysis (Section 6.10.2.1).
The following procedure will cause the Model 9110E to automatically calculate the current
NO
2
conversion efficiency.
Step one is to connect a source of calibrated NO
2
span gas as shown below.