Operating Principle - Agilent Technologies InfinityLab LC Series User Manual

1 Introduction

Operating Principle

Operating Principle

The pump head comprises two pump chambers in series with independent
high-resolution motion control. A pressure sensor in the flow path monitors the
pressure. The pump control uses this signal for minimizing the pressure ripple in
order to achieve highest flow precision. A stable flow can be delivered even in
case of eventual small internal leaks, which can be compensated automatically.
A heat exchanger between two pump chambers strongly reduces thermal effects
due to solvent compression under very high pressures.
As solvents are compressed by the pump head and expand further down the flow
path, for example in the column, the volumetric flow is changed depending on the
compressibility of the liquid. Agilent control software allows specifying pure
solvents, pre-mixed solvents and solvent gradients. Associated Agilent solvent
libraries are used by the pump control for enhanced flow accuracy, which is
required for cross-instrument or cross-system reproducibility and method
compatibility.
A high resolution encoder unit is attached to the pump drives, which divides a
single turn into 65000 steps. Each step corresponds to a volume of about 300 pL,
which allows an extremely precise control.
1260 Infinity II Flexible Pump User Manual 14