138 Advanced Operation Manual
3 Inlets
Before Pre Run
The interface is forward pressure controlled; pressure is
sensed downstream from the flow proportional valve.
During sampling
Pressure upsets caused by switching valves in the external
sampler can cause fluctuations in column flow rates. To
compensate for this, the interface is flow controlled during
sampling time. The sampling flow rate is calculated from the
pressure setpoint that is active when sample introduction
begins. This flow control starts when the GC goes into the
Pre Run state (when your system is automated and the Pre
Run light is on or during manual operation when you press
[Prep Run]) and ends after the interface’s Sampling end
setpoint expires.
Valve
Frit
Frit
Frit
Valve
EPC Module
FS = Flow Sensor
PS = Pressure Sensor
Column
FS
PS
PS
Carrier Supply
80 PSI
Septum Purge
Gas Sampling Valve
Headspace
Purge and Trap
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