Agilent Technologies Quaternary Pump 1100 Series - Manual (Page 203)

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Introduction to the Quaternary Pump
Overview
With a compressibility value set the processor calculates a compensation
volume, that is depending on the backpressure in the system and the selected
compressibility. This compensation volume will be added to the normal
stroke volume and compensates the previous described loss of volume
during the delivery stroke of the first plunger.
How Does Variable Stroke Volume Work?
Due to the compression of the pump-chamber volume each plunger stroke of
the pump will generate a small pressure pulsation, influencing the flow ripple
of the pump. The amplitude of the pressure pulsation is mainly dependent on
the stroke volume and the compressibility compensation for the solvent in
use. Small stroke volumes will generate pressure pulsations of smaller
amplitude than higher stroke volumes at same flow rates. In addition the
frequency of the pressure pulsations will be higher. This will decrease the
influence of flow pulsations on quantitative results.
In gradient mode smaller stroke volumes resulting in less flow ripple will
improve composition ripple.
The quaternary pump uses a processor-controlled spindle system to drive its
plungers. 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 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.