INFICON Composer Elite Gas Concentration Monitor - Manual (Page 65)

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Composer Elite Operating Manual
4.1.11 How to Sample Flow with a Composer Elite
When the flow through a process pipe exceeds the Acoustic Sensor’s 2000 sccm
limit, sampling of the process is required. In our experience, bypassing some of the
process gas through the Acoustic Sensor can compromise Composer Elite
precision, long term accuracy and add noise due to pressure and flow fluctuations.
Our recommendation is to “buffer” the flow through the Acoustic Sensor by adding
a Mass Flow Controller (MFC) upstream of the Acoustic Sensor in the sample
tubing. This device will stabilize the flow and in most cases restore Composer Elite
full measurement capability. In some extreme cases it may be necessary to also
add downstream buffering with a Back Pressure Controller. Try to maintain at least
200 Torr [26.66 kPa] in the Acoustic Sensor for best operation. It may be necessary
to slightly restrict the process tubing in order to induce flow through the sample
tube. See
Figure 4-7 .
An added benefit of adding the MFC to the sample tube is that flow through the
Acoustic Sensor is made visible and easily verified.
Figure 4-7 Flow sampling
MFC
Composer Elite
Acoustic Sensor
Read
Out
Back
Pressure
Controller
Pump
May require restriction to induce
flow through sample tube.
Optional:
For maximum
sensitivity or if
severe instability
exists.
Composer Elite
Sensor
Control
Unit