SPECIFICATIONS FOR ANALYSERS TO BE USED IN THE DETERMINATION OF GASEOUS COMPONENTS OF DIESEL ENGINE EMISSIONS
1 General
1.1 The analysers shall have a measuring range appropriate for the accuracy required to measure the concentrations of the exhaust gas components (see 1.5). All analysers shall be capable of being recorded. It is recommended that the analysers be operated such that the measured concentration falls between 15% and 100% of full scale.
1.2 If read-out systems (computers, data, loggers, etc.) that provide sufficient accuracy and resolution below 15% of full scale are used, concentrations below 15% of fuoo scale may also be acceptable. In this case, additional calibrations shall be made to ensure the accuracy of the calibration curves (see 5.5.2 of appendix 6 of this Code).
1.3 The electromagnetic compatibility (EMC) of the equipment shall be on a level to minimise additional errors.
1.4 Definitions
.1 The repeatability of an analyser is defined as 2.5 times the standard deviation of 10 repetitive responses to a given calibration or span gas.
.2 The zero response of an analyser is defined as the mean response, including noise, to a zero gas during a 30 seconds time interval.
.3 Span is defined as the difference between the span response and the zero response.
.4 The span response is defined as the mean response, including noise, to a span gas during a 30 seconds time interval.
1.5 Measurement error
The total measurement error of an analyser, including the cross sensitivity to other gases (see section 8 of appendix 6 of this Code). shall not exceed ±5%of the reading or ±3.5% of full scale, whichever is smaller. For concentrations of less than 100 ppm, the measurement error shall not exceed ±4ppm.
1.6 Repeatability
The repeatability of an analyser shall be no greater than ±2% of each range used below 155 ppm (or ppm C).
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1.7 Noise
the analyser peak-to peak response to zero and calibration or span gases over any 10 seconds period shall not exceed 2% of full scale on al l ranges used.
1.8 Zeri druft
The zero drift during one hour period shall be less than 2% of full scale on the lowest range used.
1.9 Span drift
The span drift during a one hour period shall be less than 2% of full scale on the lowest range used.
2 Gas drying
The optional gas drying device shall have a minimal effect on the concentration of the measured gases. Chemical dryers are not an acceptable method of removing water from the sample.
3 Analysers
The gases to be measured shall be analysed with the following instruments. For non-linear analysers, the use of linearising circuits is permitted.
.1 Carbon monoxide analyser shall be of the Non-Dispersive InfraRed(NDIR) absorption type.
.2 Carbon dioxide(CO2)analysis
The carbon monoxide analyser shall be of the Non-Dusoersuve InfraRed(NDIR) aabsorptiontype.
.3 Oxygen (O2) analysis
Oxygen analysers shall be of the Para Magnetic Detector (PMD), ZiRconimu DiOxide(ZRDO) or ElectroChemical Sensor (ECS) type.
Note: Electrochemical sensors shall be compensated for CO2 and NOx interference.
.4 Oxides of nitrogen (NOx) analysis
The oxides of nitrogen analyser shall be of the ChemiLuminescent Detector (CLD) or Heated ChemiLuminescent Detector (HCLD) type with converter maintained above 333 K (60℃)shall be used, provided the water quench check (see 8.2.2 of appendix 6 of this Code) is satisfied.