Installation manual

124 5975 Series MSD Operation Manual
4 Operating in Chemical Ionization (CI) Mode
To monitor high vacuum pressure
Procedure
1 Start up and pump down the MSD. See page 103.
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 gauge controller will not turn on if the pressure in the MSD is above
approximately 8 × 10
-3
Torr. The gauge controller is calibrated for nitrogen, but
all pressures listed in this manual are for helium.
The largest influence on operating pressure is the carrier gas (column) flow.
Table 20 lists typical pressures for various helium carrier gas flows. These
pressures are approximate and will vary from instrument to instrument.
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 manifold.
Read “Hydrogen Safety” before operating the MSD with hydrogen carrier gas.