INFICON Composer Elite Gas Concentration Monitor - Manual (Page 60)

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Composer Elite Operating Manual
4.1.5 What is the Ideal Operating Environment?
In an ideal operating environment, parameters that influence the concentration
measurement do not change. Most Reactors can be configured so that the
pressure and flow through the Acoustic Sensor are held constant by independent
controllers. The precursor’s fluence into the Reactor can be maintained or changed
without altering the total flow and pressure through the Acoustic Sensor. This is
considered good practice for Reactor design.
Leave the Composer Elite System on at all times—always ready to immediately
function with best accuracy. We have not seen deterioration through continuous
use. Since all Reactors are in environmentally controlled rooms, the small
influences due to ambient temperature changes are of no concern.
4.1.6 What is the Effect of Pressure Variation?
Because not all mixtures are purely ideal and the use of diaphragms to separate
the toxic and corrosive gases from the Exciting and Receiving microphones is
required, Composer Elite displays a small influence from pressure changes. The
effects of pressure variation on concentration are shown in
Figure 4-2 .
Figure 4-2 Effect of pressure on apparent concentration
3940
3900
3860
3820
3780
0.16
0.12
0.08
0.04
0.00
0 200 400 600 800 1000 1200
Frequency (Hz)
Absolute Pressure (Torr)
Equivalent
TMIn in H2 (mole-%)
H2- 200 sccm, 35°C
Frequency
Concentration