Installation manual

106 5975 Series MSD Operation Manual
4 Operating in Chemical Ionization (CI) Mode
To operate the reagent gas flow control module
Reagent gas flows are controlled in software (Figure 27).
The Valve Settings have the following effects:
Gas A (or B) Valve The present gas flow, if any, is turned off. The system
evacuates the gas lines for 6 minutes, then turns on the selected gas (A or B).
This is to reduce cross-mixing of the gases in the lines.
Shutoff Valve When Shutoff Valve is selected, the system turns off the present
gas flow while leaving the shutoff valve (Figure 28) open. This is to remove any
residual gas in the lines. Typical evacuation time is 6 minutes and then the
shutoff valve is closed.
The flow control hardware remembers the flow setting for each gas. When
either gas is selected, the control board automatically sets the same flow that
was used for that gas last time.
Figure 27 CI flow control