E C O P H Y S I C S Operating Guide
CLD 780 TR / July 2000 41
– “NO.c (cont.)“: The sample gas is passed through a PLC 762 photo-
lytic converter before entering the CLD 780 TR analyzer. Only NO.c is
measured and displayed. NO.c is the raw value of the sample gas
NO
x
concentration after passing through the converter and consists of
the sum of the NO and NO
2
signals. The NO
2
contribution in NO.c is
not adjusted for the converter efficiency (W
K
).
NO.c = NO + NO
2
x W
K
All the options which can be set in windows (5) to (13) are active, e.g. the
displayed NO data may be smoothed using a sliding average filter (see
windows (9) and (13)). The electronic and chemical zero point is evalu-
ated and corrected for as per the settings in the “AICI“ window (7). This
eliminates the effect of interferences in the sample, assuming the concen-
tration of the interfering substances varies directly with the NO concentra-
tion between two AIC measurements, thus ensuring that the factor
λ
NO
re-
mains practically constant (see window (58)).
Note: The measuring cycle duration MZ (the time between two consecu-
tive measurements of the same component) is given by the sum of the fol-
lowing times:
– Integration interval
∆
t (the interval for pre- and main chamber is al-
ways the same and is selected in window (24))
– Flushing time of the reactor solenoid valve SR (chosen in window (17)
– Flush time of the converter solenoid valve SC (chosen in window (17)
The measuring cycle duration MZ for the different measurement modes
can be derived as follows:
“NO“ or “NO.c“: MZ = 2x
∆
t + 2xSR
“NO and NO.c“
or
“NO and NO
2
“: MZ = 4x
∆
t + 4xSR + 2xSC
In the “CONT“ mode, the measuring cycle duration MZ may be reduced,
since the pre-chamber measurement need not be made after each main
chamber measurement. Increasing the effective measurement time in this
way is only sensible when it can be assumed that the NO concentration
and the interfering substance concentrations vary proportionately be-
tween two AIC measurements (i.e. pre-chamber measurements). The
measuring cycle duration MZ varies depending on the setting made in
windows (6) and (7). The integration time
∆
t is selectable in 0.1 sec
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