Diablo 5000B, Getting Started Manual

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Diablo 5000B Real-Time Gas Analyzer Getting Started Manual 7
Theory of Operation
Sampling Interface
The sampling interface for the Real-Time Gas Analyzer (RTGA) is shown in Figure 1.
Figure 1: The 5000B RTGA sampling interface.
The standard sampling interface consists of a sampling tee and a sampling cross. Sample input
tubing is connected to the top of the sampling tee. One branch of the tee is connected to the
sampling cross through a sample orifice, while the other is a vent line for excess sample. Since only
a small fraction of the sample input will flow through the sample orifice into the sampling cross, the
bulk of the sample can be routed back into the process or vented.
A fixed orifice (30 µm i.d.) limits the amount of sample that is drawn. The first orifice (the sample
orifice) is in between the sampling tee and the sampling cross. One branch of the cross connects to
the large “bypass” vacuum pump (Pfeifer DUO-10M, Edwards RV12, or Edwards nXDS-10i). This
pump reduces the pressure in the cross and pulls the majority of the sampled stream out to waste.
A second leg on the cross allows a precision pressure transducer to read the cross pressure. This
signal can be used to adjust the data for changes in sample pressure.
To RV12 pump
To
MSD
(10 -6 Torr)
Pressure
Transducer
Process
Stream in
Out to
vent
Molecular flow
Orifice 50

Sonic Flow
Orifice 30

Isolation
Valve
.
.
[RS232 interface]
Minimum
40ml/min flow
(350 for trace)
~0.5
Torr
Sample Tee
Sample
Orifice
HV
Orifice
To RV12 pump
To
MSD
(10 -6 Torr)
Pressure
Transducer
Process
Stream in
Out to
vent
Molecular flow
Orifice 50

Orifice 50

Sonic Flow
Orifice 30

Orifice 30

Isolation
Valve
..
..
[RS232 interface]
Minimum
40ml/min flow
(350 for trace)
~0.5
Torr
Sample Tee
Sample
Orifice
HV
Orifice