Agilent Technologies G4782A, User Manual

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16 1260 SFC Binary Pump
1
Introduction
Overview of the Hydraulic Path
How Does Variable Stroke Volume Work?
The smaller the solvent volume in the pump chamber is, the faster it can be
recompressed to operating pressure. The binary pump allows to manually or
automatically adjust the pump stroke volume of the first piston in the range of
20 – 100 μL. Due to the compression of the solvent volume in the first pump
chamber, each piston stroke of the pump will generate a small pressure
pulsation, influencing the flow ripple of the pump. The amplitude of the
pressure pulsation mainly depends on the stroke volume and the
compressibility compensation for the solvent in use. Small stroke volumes
generate less pressure pulsation than larger stroke volumes at the same flow
rate. In addition, the frequency of the pressure pulsation will be higher. This
will decrease the influence of flow pulsations on retention times.
In gradient mode, a smaller stroke volume results in less flow ripple and
reduces the composition ripple.
The binary pump uses a processor-controlled ball screw system for driving its
pistons. The normal stroke volume is optimized for the selected flow rate.
Small flow rates use a small stroke volume while higher flow rates use a higher
stroke volume.
The stroke volume for the pump is by default set to AUTO mode. This means
that the stroke is optimized for the flow rate in use. A change to larger stroke
volumes is possible but not recommended.