E C O P H Y S I C S Operating Guide
CLD 780 TR / July 2000 67
(44) “GPT NO + O
3
Ready“ window
Checking the ozone- and NO-calibration gas supply
“Gas Phase Titration NO + O
3
Ready? [Y/N]“: The operator is asked to
check if the ozone and NO calibration gas supply is ready.
– The NO cal. gas flow rate should under no circumstances be altered!
The same concentration as in window (43) has to be assured!
– Is ozone calibration gas supplied to the inlet of the photolytic converter
at atmospheric pressure? The concentration of the ozone should be be-
tween 50 and 90 % of NO(1)-concentration (see window (43)). In
other words the ozone concentration has to be high enough that the
NO(2)-concentration after mixing with ozone is 10 - 50 % of the origi-
nal NO(1).
Press “YES“: The GPT NO + O
3
step is executed. Window (45) will ap-
pear.
Press “NO“: The “Exit“-window (50) appears, and by pressing NO the
start of the calibration can be reached (window (42)).
Interrupt with “MEAS“ (window (1)).
(45) “2. Step NO + O
3
“-window
Gas phase titration NO + O
3
“2. Step NO + O
3
Calibrating“:
Second step of the GPT, where NO(2) and NO.c(2) concentrations are
measured (after NO cal gas is mixed with ozone). The NO(2) value
should fall to 10 - 50 % of the original concentration (see window (43).
Again the two values, NO(2) and NO.c(2) are displayed after each cy-
cle, and again only after the concentrations are stable enough will the
measurement be accepted. Everything else is the same as described in
window (43)).
If the values are stable, the analyzer automatically registers the values
and window (46) appears.
Caution: In the absence of sufficiently stable calibration gas, GPT is
not possible. Window (45) remains active to indicate this (“Cal. gas
supply or calibrator needs to be checked“).
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