E C O P H Y S I C S Practical hints
CLD 780 TR / July 2000 96
– Periodically check the raw signal under the same conditions as above,
and compare the values obtained. If the value is <60 % of the raw sig-
nal obtained with clean chambers, this indicates that the reaction
chambers (and possibly the gas lines) need cleaning (see 9.4 and
9.5).
Hint:
If after cleaning the chamber the values are still significantly lower than
the initial raw signal, the gas lines need cleaning.
If it can be confirmed that the desired cal. gas concentration is being sup-
plied to the inlet of the analyzer and the sample gas and dry air filter are
functioning correctly (see 9.1 and 9.2), all gas carrying lines in the ana-
lyzer and PLC 762 (if appropriate) must be checked and if necessary
cleaned. Especially sensitive to contamination are the flow restrictors:
Flow restrictors in the CLD 780 TR: (see Fig. 3.1 & 3.2)
– Ozone generator outlet (4)
– PMT housing flush outlet (11)
– Sample gas line (2)
To clean or replace flow restrictors:
1. mark the position of the fittings
2. open fitting and either clean flow restrictor in an ultrasonic bath, or
replace
3. reposition flow restrictor plate and retighten fittings to the marked posi-
tion
Remark: When fitting a new flow restrictor:
1. tighten fitting initially only finger tight
2. tighten further exactly 1/8 turn with a wrench
Caution: Any such comparison is only meaningful if the raw values are
acquired under identical analyzer parameter settings (cal. gas conc.,
range, integration interval, number of cycles) and under similar ambi-
ent conditions (temp. and pressure).
Caution: After this action analyzer and photolytic converter must be
calibrated!
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