Ecotech Serinus 44 - 3. Operation of the Serinus 44; 3.1 Warm-Up and 3.2 Measurement

Operation
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3. Operation
3.1 Warm-Up
When the instrument is first turned on it must go through a period of adjustment and calibration. No
measurements are taken during this warm-up period.
The following activities occur during warm-up:
Adjust High Voltage
The high voltage digital pot is adjusted to set the high voltage supply to the PMT for optimal range
and performance.
Converter is Cold/Warm/Hot
The instrument progressively increases the temperature of the NO
2
to NO converter until it reaches
the desired temperature of 325°C. When heating from cold the NO
2
converter will take
approximately 60 minutes to reach the desired temperature. When the converter reaches 250°C the
ozone generator will be switched on and analysis of NO/NO
2
/NO
X
/NH
3
/N
X
will begin.
The NH
3
converter temperature is maintained by the external converter and assumed to take a
similar time to the internal NO
2
to NO converter to reach operational temperature.
After this warm-up has completed the instrument will immediately begin making measurements
(refer to Section 3.2).
3.2 Measurement
The Serinus 44 NO
X
Analyser is a five channel monitoring instrument that measures sample air
through three different flow paths. These three paths are used to measure NO, NO
X
and N
X
. From
these measurement cycles two calculations are performed to get measurements of NO
2
(difference
between NO and NO
X
) and NH
3
(difference between NO
X
and N
X
).
First a background is performed to determine the level of fluorescence without NO present, thus
removing any background noise from the signal.
The instrument measures NO, NO
X
and N
X
in sequence. It performs this cycle five times before doing
another background. The sample fill immediately after a background is longer than usual, to clear the
measurement cell. One full cycle takes one minute and forty five seconds to complete.
Table 2 – Measurements Times
Instrument State
Duration (seconds)
Description
Background Fill
8
Cell fills with background air.
Background Meas
3
Background air is measured.
NO Sample Fill
3
*+4
Cell fills with NO sample.
* The first sample fills after a background is longer.