E C O P H Y S I C S Operating Guide
CLD 780 TR / July 2000 72
(56) “NO Calibration Gas Ready?“-window
Prompts the operator to check the NO-calibration gas supply.
– Is calibration gas being supplied at atmospheric pressure to the NO
x
Cal gas inlet of the photolytic converter or to the CLD 780 TR sample
inlet?
– If using a gas calibrator, has it been adequately purged?
–etc.
Press “YES“ to start the NO calibration . Window (57) appears.
Press “NO“ to abort. The “Exit“-window (60) appears, allowing the op-
tion to return to the start of the calibration (window (51)).
Press “MEAS“ to abort the calibration and return to measure (window
1a).
(57) “Cycle Zero NO“ window
fNO and
λ
NO determination.
“Cycle Zero NO“: the fNO and
λ
NO determination is initiated. A single
cycle consists of a pre-chamber measurement (P) and a main chamber
measurement (M). Each measurement itself consists of:
– the pre- and main chamber integration interval
∆
t
AIC
, set in window (6)
“Int.-Time for Cal. and AICI“.
– the solenoid valve purging time SR, set in window (17), “Rea“- Delay.
The total cycle duration C is given by:
C = 2 x
∆
t
AIC
+ 2 x SR
The software begins to count down automatically from 255 to 0. If within
this time the calibration is not manually accepted by the user pressing the
“YES“ key, then the analyzer returns directly to the “CONT“ measuring
mode, window (1a).
The accuracy of the calibration can be further improved by use of the
Calibration Sliding Average Filter. The width of this filter, which is set in
window (6) “Cal. Slidefilter Time“, should be a multiple of the cycle dura-
tion C. For best results do not validate the calibration until at least one
complete slide filter width duration has elapsed since the start .
The measured pre-and main chamber signals are shown on the display
under the headings “ZERO“ and “NO“.
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