Agilent Technologies 1260 Infinity II User Manual page 16

1
Introduction
Overview of the Hydraulic Path
the inner diameter of the pump-head chamber allowing the solvent to fill the
gap in between. The first piston has a stroke volume in the range of 20 μL to
100 μL depending on the flow rate. The microprocessor controls all flow rates
in a range of 1 μL/min to 5 mL/min. The inlet of the first pumping unit is
connected to the active inlet valve which is processor-controlled opened or
closed allowing solvent to be drawn into the first pump unit.
The outlet of the first pump chamber is connected by a 500 μL absorber
capillary to the second pump chamber. The outlets of the second chambers of
both pump channels joined via a small mixing chamber. A coiled restriction
capillary connects the mixing chamber via a pressure pulse damper, a mixer
and a pressure sensor to the purge valve assembly. The outlet of the purge
valve assembly is then connected to the attached chromatographic system.
When turned on, the pump runs through an initialization procedure to
determine the upper dead center of the first piston of both pump channels.
The first piston moves slowly upwards to the mechanical stop of the pump
head and from there it moves back a predetermined path length. The
controller stores this piston position in memory. After this initialization the
pump starts operation with the set parameters for the two pump channels.
The active inlet valve is opened and the down moving piston draws solvent
into the first pump head. At the same time the second piston is moving
upwards delivering into the system. After a controller defined stroke length
(depending on the flow rate) the drive motors are stopped and the active inlet
valve is closed. The motor direction is reversed and moves the first piston up
until it reaches the stored upper limit and at the same time moving the second
piston downwards.
Then the sequence starts again moving the pistons up and down between the
two limits. During the delivery stroke of the first piston the solvent in the
pump head is pressed through the outlet valve into the second pumping unit.
The second piston draws in half of the volume displaced by the first piston and
the remaining half volume is directly delivered into the system. During the
drawing stroke of the first piston, the second piston delivers the drawn
volume into the system.
For pump specifications, see
16
"Performance Specifications"
InfinityLab LC Series 1260 Infinity II Binary Pump User Manual
on page 30.