Filter
Top Products
Teledyne API - Model 200EH/EM Operation Manual Getting Started
17
If your application is not a measurement in ambient air, the zero calibration gas should be matched to
the matrix of the measured medium. Pure nitrogen could be used as a zero gas for applications where
NO
X
is measured in nitrogen. Special considerations apply if measuring NO
X
in a matrix that does not
contain oxygen, see Section 10.3.11 for more information.
span gas
A gas specifically mixed to match the chemical composition of the
type of gas being measured at near
full scale of the desired measurement range. In this case, NO
X,
NO and NO
2
measurements made with
the M200EH/EM, 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 between 0 ppm and 500 ppm, an appropriate span gas
concentration would be 400 ppm NO
x
.
Even though NO gas in nitrogen could be used as a span gas, the matrix of the balance gas is different
and may cause interference problems or yield incorrect calibrations. The same applies to gases that
contain high concentrations of other compounds (for example, CO
2
or H
2
O). The span gas should
match all concentrations of all gases of the measured medium as closely as possible.
Cylinders of calibrated NO gas traceable to NIST-standard reference materials specifications (also referred
to as EPA protocol calibration gases) are commercially available.
Table 3-6: NIST-SRM's Available for Traceability of NO
x
Calibration Gases
NIST-SRM
4
TYPE
NOMINAL
CONCENTRATION
2627a
2628a
2629a
Nitric Oxide (NO) in N
2
Nitric Oxide (NO) in N
2
Nitric Oxide (NO) in N
2
5 ppm
10 ppm
20 ppm
1683b
1684b
1685b
1686b
1687b
Nitric Oxide (NO) in N
2
Nitric Oxide (NO) in N
2
Nitric Oxide (NO) in N
2
Nitric Oxide (NO) in N
2
Nitric Oxide (NO) in N
2
50 ppm
100 ppm
250 ppm
5000 ppm
1000 ppm
2630
2631a
2635
2636a
Nitric Oxide (NO) in N
2
Nitric Oxide (NO) in N
2
Nitric Oxide (NO) in N
2
Nitric Oxide (NO) in N
2
1500 ppm
3000 ppm
800 ppm
2000 ppm
2656
2660a
Oxides of Nitrogen (NO
x
) in Air
Oxides of Nitrogen (NO
x
) in Air
2500 ppm
100 ppm
NOTE:
If a dynamic dilution system such as the Teledyne Instruments model 700 is used to
dilute high concentration gas standards to low, ambient concentrations, Make sure that:
The NO concentration of the reference gas matches the dilution range of the calibrator.
Choose a NO gas concentration that is in the middle of the dilution system’s range.
04521C (DCN5731)