1260 Infinity Binary Pump User Manual 17
Introduction to the Binary Pump
1
Overview of the Hydraulic Path
When both solvent compressibility at the current operating pressure and
pump elasticity are known, the pump can automatically correct for the
missing volume by drawing the appropriate larger solvent volume at
ambient pressure and speed up the piston during the recompression phase
in the first pump chamber. As a result, the pump delivers the accurate
volume with any (calibrated) solvent at any pressure at a greatly reduced
pressure ripple. For applications that require lowest transition volume of
the pump, damper and mixer can be bypassed.
For compatibility with older methods from G1312A Binary Pumps, the
previous one- point compressibility compensation is available, too.
However, since the compressibility is a non- linear function, one single
compressibility value per solvent will only give good results at one
particular pressure
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.
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