E C O P H Y S I C S Operating Guide
CLD 780 TR / July 2000 43
(4) “Recorder“-window
Enables analog output settings to be adjusted
1. “Mode“: select 1 V, 10 V or 20 mA full scale for the analog output.
2. “Fullscale“: 50 % or 100 % of the selected current measurement
range
3. “Offset“: select 20 % or none. With an offset of 20 % the zero line is
shifted by 20 % of fullscale. The remaining 80 % will cover, however,
the full range (e.g. 100 ppb). By selecting “Offset 20 %“, in 20 mA
“Mode“ an analog output of 4 - 20 mA is created.
Exit window using “MEAS“ or “MENU“ keys.
(5) “Cont.Meas“-window
“Continuous“ measuring of NO or NO.c with freely selectable determina-
tion of the interference coefficient
λ
NO
.
It is important to remember that in both NO and NO.c measuring modes,
each measurement cycle is followed by a zero point acquisition cycle of
equal length. In addition the valve purge times (see “Param.“ window
(17), “Rea“) extend the total integration time. A complete cycle for both
NO and NO.c measurement therefore requires 2 integration times plus
twice the solenoid valve flushing time.
If there is the need for much shorter integration time (fast response) the
“Cont.Meas“ (5) -window offers the option to reduce this time.
The operator can freely select, within certain limits, the period between in-
terference coefficient (
λ
NO
)determinations.
The duration of
λ
NO
determination, T
AICA
, is made up as follows:
– the integration time
∆
t
AIC
for the pre and main chamber measurements.
See window (6) “Int.-Time for Ca. & AICI“
– the purge time for the gas tubing, SP. See window (7), “Purge-time“.
– the purge time for the solenoid valve SR. See window (17), “Rea-
Delay“.
The total duration is:
T
AICA
= 2x
∆
t
AIC
+ 2xSP + 2xSR
T
AICA
is at least 8 secs, since
∆
t
AIC
cannot be selected less than 3 secs, SP
may be set to 0 secs and SR must be at least 1000 ms.
The interval between automatic
λ
NO
determinations is set in window (7),
“AICI-Time“. This must be greater than T
AICA
.
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