E C O P H Y S I C S Operating Guide
CLD 780 TR / July 2000 70
(52) “Zero-Air ready?“ window
Check if zero-air supply is ready
“Zero-Air ready? [Y/N]“: The operator is asked to check the zero air sup-
ply.
– Is zero-air supplied at atmospheric pressure to the sample inlet of the
analyzer or the PLC 762? Zero air must be connected to the “NO
x
Cal“-inlet if no external unit controls the solenoid valve “NO
x
Cal/Zero-Air“. This valve is not controlled by the CLD 780 TR.
– If a calibrator is used, has it been purged sufficiently?
–etc.
“YES“ key: The S
Null
determination is executed. Window (53) appears.
“NO“ key: The “Exit“-window (60) appears, allowing the option to return
to the starting point of the analyzer calibration (window (51)) or to meas-
ure mode.
Interrupt with “MEAS“ and return to measuring mode.
(53) “Cycle ZERO NO“ window
Proceed with the S
Null
determination.
“Cycle ZERO NO“: the S
Null
determination is initiated. A single cycle con-
sists of a pre-chamber measurement (P) and a main chamber measure-
ment (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 S
Null
determination is not manually accepted by the user press-
ing 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 of the S
Null
determination.
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