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and importance of such increases shall be considered when
preparing to make measurements. If better performance is
necessary, then appropriate precautions shall be taken.
The insmrnent to be used shall be such as to maintain the
temperature of the detector and sample-handling components
at a set point temperature within the range 155°C to 165OC to
a stability of 22'C. The leading specification points shall be
as follows, the detector response having been optimized and
the instrument generally having stabilized:
a) Total range: 0 to 5 000 ppmC in appropriate ranges.
Note.- In application there are two aspects of
performance which can affect the accuracy of measurement:
a) the oxygen efsect (whereby differing proportions of
oxygen present in the sample give differing indicated
hydrocarbon concentration for consrant tactual HC
concentrations); and
b) the relative hydrocarbon response (whereby there is
u diflerent response to dte same sample hydrocurbon
concentrations expressed as equivalent ppmC,
dependent on the class or admixture of clusses of
hydrocarbon compounds). ,
The magnitude of the effects noted above shall be
determined as follows and limited accordingly.
Oqgen response: measure the response with two blends
of propane, at approximately 500 ppmC concentration known
to a relative accuracy of 41 per cent, as follows:
b) Resolution: better than 0.5 per cent of full scale of 1) propane in 10 2 1 per cent O,, balance N,
range used or 0.5 p p d , whichever is greater.
2) propane in 21 -c 1 per cent 0,, balance N2
c) ~e~eatabilitbye:t ter than +I per cent of full s~ale If R, and R, ac the respective nonndized responses then
range used, or 20.5 ppmC, whichever is greater. (R, - R,) shall be less than 3 per cent of R,.
d) Stability: better than +2 per cent of full scale of range
used or k1.0 ppmC, whichever is greater, in a period
of 1 hour.
e) Zkro drift: less than +I per cent of full scale of range
used or 20.5 ppmC, whichever is greater, in a period
of 1 hour.
f ) Noise: 0.5 Hz and greater, less than 21 per cent of
full scale of range used or a . 5 ppmC, whichever is
greater.
D~fferential hydrocarbon response: measure the response
with four blends of different hydrocarbons in air, at
concentrations of approximately 500 ppmC, hown to a
relative accuracy of *1 per cent, as follows:
a) propane in zero air
b) propylene in zero air
c) toluene in zero air
d) n-hexane in zero air.
ANNEX 16 - VOLUME 41 27
Annex 16 - Environmenml Protection Volume I1
If R,, R,, R, and R, are, respectively, the normalized
responses (with respect to propane), then (R, - R,), (R, - R,)
and (R, - Rd) shall each be less than 5 per cent of R,.
3. OPTIMIZATION OF DETECTOR
RESPONSE AND ALIGNMENT
3.1 The manufacturer's instructions for initial setting up
procedures and ancillary services and supplies required shall
be implemented, and the instrument allowed to stabilize. All
setting adjustments shall involve iterative zero checking, and
correction as necessary. Using as sample a mixture of
approximately 500 ppmC of propane in air, the response
characteristics for variations first in fuel flow and then, near
an optimum fuel flow, for variations in dilution air flow to
select its optimum shall be determined. The oxygen and
differential hydrocarbon responses shall then be determined
as indicated above.
3.2 The linearity of each analyser range shall be
checked by applying propane in air samples at concentrations
of approximately 30, 60 and 90 per cent of full scale. The
maximum response deviation of any of these points from a
least squares straight line (fitted to the points and zero) shall
not exceed d p r cent of full scale value. If it does, a
calibration curve shall be prepared for operational use.
ATTACHMENT B TO APPENDIX 3. SPECIFICATION FOR
CO AND CO, ANALYSERS
Note.- Paragraph 5.3 of Appendix 3 summarizes the
characteristics of the analysis sub-system to be employed for
the individual measurements of CO and CO, concentrations
in the exhaust gas sample. The instruments are based an the
principle of non-dispersive absorption of infra-red radiation
in parallel reference and sample gas cells. The required
ranges of sensitivity are obtained by use of stacked sample
cells or changes in electronic circuitry or both. Interferences
from gases with averlapping absorption bands may be minimized
by gas absorption$fiUers and/or opticalfilters, preferably
e) Zero drifr: less than k1 per cent of full scale of range
used or *2 ppm, whichever is greater, in a period of
1 hour.
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