48 Operation Manual
3 Operating in Electron Impact (EI) Mode
Pumping Down
Pumping Down
The data system helps you pump down the MS. The process is
mostly automated. When you turn on the main power switch
(while pressing on the analyzer sideplate), the MS pumps down
by itself. The data system software monitors and displays
system status during pumpdown. When the pressure is low
enough, the program turns on the ion source and mass filter
heaters and prompts you to turn on the GC/MS interface heater.
The MS will shut down if it cannot pump down correctly.
Using the MS monitors, the data system can display:
• Motor speed for each MS turbo pump
• Analyzer chamber pressure (vacuum)
• Quadrupole and ion source temperatures
Controlling Temperatures
MS temperatures are controlled through the data system. The
MS has independent heaters and temperature sensors for the
ion source and the quadrupole mass filter. You can adjust the
setpoints and view these temperatures from the data system
The GC/MS interface heater is powered and controlled by the
Thermal Aux #2 heated zone of the GC. The GC/MS interface
temperature can be set and monitored from the data system or
from the GC keypad.
Controlling Column Flow
Carrier gas flow is controlled by column inlet pressure in the
GC. For a given inlet pressure, column flow will decrease as the
GC oven temperature increases. With electronic pneumatic
control (EPC) and the column mode set to Constant Flow, the
same column flow is maintained regardless of temperature.
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