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Jun 2001
Inlets
Agilent 6890 Gas Chromatograph Service Manual
Programmed Temperature Vaporization Inlet (PTV) 240
Split modes
Split modes
Septum head installed
In the two split modes—with or without a pressure pulse—the solenoid valve
is open and divides the gas stream entering the inlet between the column flow,
the split vent flow through the solenoid valve, and the septum purge flow. The
ratio of the split vent flow to the column flow is called the split ratio.
Figure 240-1 shows the inlet flow control. Overall carrier and sample gas flow
is controlled by the first proportional valve and the flow sensor. The solenoid
valve is open, and proportional valve 2 acts as a back pressure regulator
controlled by the pressure sensor on the septum purge vent line.
Figure 240-1 Split mode flow control diagram (septum head installed)
PV1
PV2
FS
SPR
PS
Split
vent
SPR
vent
Flow
limiting
frit
Tota l fl ow
control loop
Septum
holder
Tra p
To det e ct or
Te m p e r at u r e
conversion
board
Cryo
valve
Valve
open
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