Document ID: chunk:federal_register_of_legislation:F2024L00447:reg:0:p25
Version: federal_register_of_legislation:F2024L00447
Segment Type: reg
Provision Reference: reg 0 (pt 25/57)
Character Range: 161269–164040

the analyser reading. A check for interference effects and the correct functionality of analysers shall be performed by the analyser manufacturer prior to market introduction at least once for each type of analyser or device addressed in paragraphs 4.3.5. (b) to (f).

              (b) CO analyser interference check

                  Water and CO2 can interfere with the measurements of the CO analyser. Therefore, a CO2 span gas, having a concentration of 80 to 100 per cent of the full scale of the maximum operating range of the CO2 analyser used during the test, shall be bubbled through water at room temperature and the analyser response recorded. The analyser response shall not be more than 2 per cent of the mean CO concentration expected during normal on-road testing or ± 50 ppm, whichever is larger. The interference check for H2O and CO2 may be run as separate procedures. If the H2O and CO2 levels used for the interference check are higher than the maximum levels expected during the test, each observed interference value shall be scaled down by multiplying the observed interference with the ratio of the maximum expected concentration value during the test and the actual concentration value used during this check. Separate interference checks with concentrations of H2O that are lower than the maximum concentration expected during the test may be run and the observed H2O interference shall be scaled up by multiplying the observed interference with the ratio of the maximum H2O concentration value expected during the test and the actual concentration value used during this check. The sum of the two scaled interference values shall meet the tolerance specified in this point.

              (c) NOX analyser quench check

                  The two gases of concern for CLD and HCLD analysers are CO2 and water vapour. The quench response to these gases is proportional to the gas concentrations. A test shall determine the quench at the highest concentrations expected during the test. If the CLD and HCLD analysers use quench compensation algorithms that utilize H2O or CO2 measurement analysers or both, quench shall be evaluated with these analysers active and with the compensation algorithms applied.

                     (i) CO2 quench check

                     A CO2 span gas having a concentration of 80 to 100 per cent of the maximum operating range shall be passed through the NDIR analyser; the CO2 value shall be recorded as A. The CO2 span gas shall then be diluted by approximately 50 per cent with NO span gas and passed through the NDIR and CLD or HCLD; the CO2 and NO values shall be recorded as B and C, respectively. The CO2 gas flow shall then be shut off and only the NO span gas shall be passed through the CLD or HCLD;