1065.270—Chemiluminescent detector.
(a) Application.
You may use a chemiluminescent detector (CLD) to measure NOX concentration in raw or diluted exhaust for batch or continuous sampling. We generally accept a CLD for NOX measurement, even though it measures only NO and NO2, when coupled with an NO2 -to-NO converter, since conventional engines and aftertreatment systems do not emit significant amounts of NOX species other than NO and NO2. Measure other NOX species if required by the standard-setting part. While you may also use other instruments to measure NOX, as described in § 1065.272, use a reference procedure based on a chemiluminescent detector for comparison with any proposed alternate measurement procedure under § 1065.10.
(b) Component requirements.
We recommend that you use a CLD that meets the specifications in Table 1 of § 1065.205. Note that your CLD-based system must meet the quench verification in § 1065.370 and it must also meet the linearity verification in § 1065.307. You may use a heated or unheated CLD, and you may use a CLD that operates at atmospheric pressure or under a vacuum. You may use a CLD that has compensation algorithms that are functions of other gaseous measurements and the engine's known or assumed fuel properties. The target value for any compensation algorithm is 0.0% (that is, no bias high and no bias low), regardless of the uncompensated signal's bias.
(c)
NO
2
-to-NO converter. Place upstream of the CLD an internal or external NO2 -to-NO converter that meets the verification in § 1065.378. Configure the converter with a bypass line if it is needed to facilitate this verification.
(d) Humidity effects.
You must maintain all CLD temperatures to prevent aqueous condensation. If you remove humidity from a sample upstream of a CLD, use one of the following configurations:
(1)
Connect a CLD downstream of any dryer or chiller that is downstream of an NO2 -to-NO converter that meets the verification in § 1065.378.
(2)
Connect a CLD downstream of any dryer or thermal chiller that meets the verification in § 1065.376.