Split Modes; Septum Head Installed - Agilent Technologies 6890 Series Service Manual

Gas chromatograph

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Split modes

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

Programmed Temperature Vaporization Inlet (PTV)

control loop

Split mode flow control diagram (septum head installed)

Agilent 6890 Gas Chromatograph Service Manual

6890a 6890 plus