Sampling Unit; Needle-Drive - Agilent Technologies 1220 Infinity II LC User Manual

When the metering unit has drawn the required volume of sample into the
sample loop, the needle is raised, and the vial is replaced in the sample tray.
The needle is lowered into the needle seat, and the injection valve switches
back to the mainpass position, flushing the sample onto the column.
Figure 34

Sampling Unit

The sampling unit comprises three main assemblies: needle drive, metering
device, and injection valve.
The replacement sampling unit excludes the injection valve and metering head
N O T E
assemblies.

Needle-Drive

The needle movement is driven by a stepper motor connected to the spindle
assembly by a toothed belt. The circular motion of the motor is converted to
linear motion by the drive nut on the spindle assembly. The upper and lower
needle positions are detected by reflection sensors on the sampling unit flex
1220 Infinity II LC System User Manual
Mainpass Position (Sample Injection)
Injection System Description
Autosampler
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