Flow and Pressure Control Part 1. Electronic Pneumatic Control (EPC)
Configure the column
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Additional notes on column configuration
• Vacuum correct—If the detector exhausts into the atmosphere, this
parameter should be Off. If a column is connected directly to a mass selective
detector, the parameter should be On. This allows the GC to compensate for
either the local atmospheric pressure (Off) or for the reduced pressure in a
mass selective detector (On).
• Pres correct—Some detectors, such as an atomic emission detector,
operate at pressures that are neither atmospheric or vacuum. This parameter
lets the user enter an appropriate pressure value.
• Packed columns should be entered as column not defined. To do this, enter
0 for either column length or column diameter.
• You should check configurations for both columns to verify that they specify
separate inlets. If you are only using one column, it is still important that the
second column be indicated for a different inlet, even if it is undefined.
Failure to do this will lead to some very unusual flow calculations.
It is possible, and sometimes appropriate, to configure both installed
columns to the same inlet.
• Some pneumatic setpoints change with oven temperature because of
changes in column resistance and in gas viscosity. This may confuse users
who observe pneumatics setpoints changing when their oven temperature
changes. However, the flow condition in the column remains as specified by
the column mode (constant flow or pressure, ramped flow or pressure) and
the initial setpoint values.
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