Environnement MIR 9000 - LCD, Technical Manual

Page: 134 / 154

MIR 9000 Duplication prohibited
5–20
February 2000
Each sequence is defined by a position of the wheel of optical filters FILTER and a position of the
wheel of cells for the gaseous correlation CELL .
These positions are defined in the control documents.
For information purposes, the NH
3
measurement is made by gaseous correlation. The same optical
filter is used for the MEASURE sequence and the REFERENCE sequence ( FILTER = 02 in our
example). By contrast, in MEASURE , one cell filled with nitrogen is placed on the optical path
( CELL = 03 in our example) and, in REFERENCE , one cell filled in NH
3
is placed on the optical path
( CELL = 02 in our example).
The H
2
O measurement is made by double wavelength. The cell filled with nitrogen ( CELL = 03 in our
example) is used for the MEASURE sequence and for the REFERENCE sequence. By contrast, in
MEASURE , a specific optical filter H
2
O is placed on the optical path ( FILTER = 03 in our example)
and, in REFERENCE , one specific optical filter is placed on the optical path ( FILTER = 04 in our
example).
The parameters of this menu enable configuring the acquisition and the sequences.
Number of Arches : number of arches for each sequence (MEASURE NH3 for example). The arches
are obtained physically by the chopper.
Number of Samples : number of samplings made on each arch. This parameter defines the electronic
sampling.
Number of Cycles : a cycle is divided into a MEASURE sequence and a REFERENCE sequence. For
each gas, a certain number of cycles is made.
In our example, 10 NH
3
cycles are made, followed by 2 H
2
O cycles and so on.
Delay 1: Time (in msec) between each MEASURE and REFERENCE sequence.
Delay 2 : time (in msec) between the sampling on the low level of the signals and the sampling on the
high level of the signals.
Delay 3: Time (in 10 *msec) between each gas measured.
In our example, this delay occurs after the NH
3
cycles or before the start of the H
2
O cycles.