194 1100 Series Nano Pump Service Manual
5 Introduction to the Nano Pump
Introduction to the Nano Pump
The nano pump consists of two identical pumping units in a single housing. It
generates gradients by high-pressure mixing. A solvent selection valve
provides flexibility in the choice of solvents.
Mobile phase composition is produced by mixing the outputs of pump A and
pump B. The solvent selection valve allows the pump A output to originate
from either channel A1 or channel A2. The pump B output may originate from
either channel B1 or channel B2.
The primary flow produced by the two pumping units is proportioned in an
electomagnetical proportional valve (EMPV). The remaining column flow is
measured in a mass flow sensitive flow sensor. The measured flow is
compared with the user-entered column flow setpoint. The flow sensor
controls the EMPV current, causing the EMPV to correctly proportion the
column flow. The primary flow in excess of the required column flow volume
is derivated to the waste.
Solvent degassing is not done directly in the pump. A 4-channel, low volume
micro vacuum degasser, available as a separate module, provides degassed
solvents to the pump channel inputs. Solvent degassing is required for best
flow stability and detector stability, especially at the low flow rates required to
run nano LC applications.
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