9. Allow the instrument to achieve a prolonged, stable measurement response and note down the
NO, NO
2
and
N
X
values. Label them as [NO]
FINAL
, [NO
2
]
FINAL
and [N
X
– NO]
FINAL
(after the user
performs the calculation of N
X
– NO).
10. Use these noted measurements to calculate the converter efficiency using Equation 4.
11. Repeat steps 8 to 10 for a minimum of two more O
3
points, spread across the measurement
range of the instrument and note down the results.
12. Average the efficiencies. If the calculated result is above 96% efficient than the test has passed
enter the result as the new Conv. Efficiency NO2. If the converter efficiency is below 96%, the
test has failed and the converter may require replacement. Try repeating the test and make sure
there are no issues with your calibration system. Ensure there is no drift in NO span or generated
O
3
during the test.
13. Open - Main Menu Calibration Menu.
14. Edit - Conv. Efficiency NO2 - (enter averaged efficiency result (only if test passed)) - Accept.
5.8 NH
3
Converter Efficiency
The efficiency of the external converter, NH
3
scrubber and second NO
2
to NO converter coil must be
determined to correctly measure NH
3
. The combined losses of all three components are referred to
as the NH
3
Converter Efficiency. The NH
3
converter efficiency should be greater than 80% for the
instrument to be operating correctly.
To calculate and correct converter efficiency the following equation is used:
Equation 6 – Calculation for NH3 Converter Efficiency
= NH
3
measurement obtained by running a stable concentration of NH
3
span gas
through the instrument with the converter efficiency field set to 100.
= NH
3
concentration supplied from the gas dilution system via NH
3
gas standard.
5.8.1 Single Point NH
3
Converter Efficiency Check
This procedure is a simple check to ensure the converter efficiency for the NH
3
converter has not
drifted significantly from the expected value (from a previous multipoint adjustment). The NO, NO
2
and NO
X
values can be ignored during this test.
Equipment Required
Gas Dilution Calibrator (such as a Serinus Cal 1000/2000/3000)
NH
3
gas cylinder reference standard
Zero Air Generator
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