Installation manual

Operating in Electron Impact (EI) Mode 3
5975 Series MSD Operation Manual 71
To monitor high vacuum pressure
Pressure monitoring requires an optional G3397A Micro-Ion vacuum gauge.
Materials needed
• Micro-Ion vacuum gauge (G3397A)
Procedure
1 Start up and pump down the MSD (page 91).
2 In the Tune and Vacuum Control view select Turn Vacuum Gauge on/off from
the Vacuum menu.
3 In the Instrument Control view you can set up an MS Monitor for reading.
The vacuum can also be read on the LCP or from the Manual Tune screen.
The largest influence on operating pressure in EI mode is the carrier gas
(column) flow. Table 13 lists typical pressures for various helium carrier gas
flows. These pressures are approximate and will vary from instrument to
instrument by as much as 30%.
WARNING
If you are using hydrogen as a carrier gas, do not turn on the Micro-Ion vacuum
gauge if there is any possibility that hydrogen has accumulated in the analyzer
chamber. Read “Hydrogen Safety” before operating the MSD with hydrogen carrier
gas.