Using the Active Method
3-22
Initial Carrier-Gas Setpoint
The carrier gas mass-flow controller receives set points of flow or pressure depending on
the configured carrier gas mode. The program calculates the initial set point from the
active GC method. The initial set point is established upon setting up a method, ending a
run, or resetting the GC. The flow rate is held constant at the initial value if no additional
carrier-flow entries are made in the GC method. The controller receives pressure set
points when operating in the pressure control mode.
Carrier-Gas Program
The GC method accommodates up to three additional carrier-gas program steps each
consisting of a hold time, ramp rate, and plateau set point. Sequential set points may be
greater than or less than the preceding set point. The PPC system programs the carrier-
gas controller with a positive or negative ramp as required.
At the end of the GC oven program, the carrier gas resets to the initial set point value in
the method even if a carrier-gas program is in progress. The carrier gas also resets if the
end of the carrier-gas program occurs before the end of the oven program.
Carrier-Gas Timed Events
You can also use timed events to produce step changes in the set point. Carrier-gas events
can occur before or after a run starts. A carrier-gas event supersedes the method set point
value at the time the event occurs. However, if the carrier-gas program in the method
advances to a new step after a carrier-gas event, the new program step or ramp takes
control.
Leak Checking
The Clarus GC monitors the inlet pressure with a carrier gas mass-flow controller in use.
After selecting the carrier-gas Flow mode in configuration, you can enter the maximum
inlet pressure value. If the inlet pressure drops below or rises above the set limit for more
than one minute, a warning message appears.
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