Teledyne API – Ultra Sensitivity Model T200UP NO/NO
2
/NOx Analyzer Addendum to T200
16 07450B DCN6495
EPA Protocol Calibration section. This sets the NO and NOx slopes
for each channel.
5. Note, a hardware adjustment of the PMT may be required, by
adjusting the HVPS, in order to get the NO & NOx slopes to be close
to 1.000. Refer to PMT Sensor Hardware Calibration in the
Troubleshooting and Repair section of the T200 Operation Manual.
6. Calibrate the photolytic converter efficiencies at 10-20% and 80-90%
of the expected NO
2
range (details provided next in Section 4.1.2)
using either bottled NO
2
balanced in nitrogen or by conducting a low
level GPT using a T700U calibrator.
Note
The photolytic converter dissociates the NO
2
Molecule into NO + O. The
free radical oyxgen atoms combine with ambient O
2
to form O
3
. The
excess NO used during GPT will react with the byproduct O
3
, which in
turn affects the calculated NO
2
concentration. If calibrating using GPT
the amount of excess NO should be kept to a minimum.
The Ozone generated as part of the photolytic process back titrates the
converted NO. This phenonemnon is non-linear and leads to a situation
where the calculated CE value is less at higher concentrations of NO
2
.
Example:
At 50 PPB of NO
2
the CE value is Typically CE = 28/50 = 0.5600
At 400 PPB of NO
2
the CE value is CE = 200/400 = 0.5000
The software allows calibration of the CE value at two NO
2
concentration
points, A and B. Thereafter, the software corrects the measured NO
2
concentration based on a calculated slope and offset. Concentration
values entered for the B parameter are higher than those entered for A.
Therefore, it is recommended that the user calibrate the B point first, so
that the higher concentration of NO
2
helps to stabilize the pneumatic
tubing.
4.1.2 Converter Efficiency (CE) Points (A&B) Calibration
High Value NO
2
concentration, Point B:
1. Deliver 80-90% of selected range for NO
2
(if using GPT, keep excess
NO at or below 20ppb), and allow the analyzer to sample for an
adequate period to achieve stability and display the measured NOx,
NO and NO
2
concentrations.
2. Enter the actual NO
2
concentration being delivered into the NO2B
menu of the CAL>CONC>CONV menu, and press ENTR. The actual
NO
2
concentration, if using GPT to generate the gas, is equal to the
difference between the NO being delivered and the measured NO
remaining as part of the GPT.
3. Exit to the SETUP menu and allow the analyzer to sample for an
adequate period to achieve stability.
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