Agilent Technologies 1100 Series, Service Manual

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196 1100 Series Nano Pump Service Manual
5 Introduction to the Nano Pump
Each channel consists of an identical, independently controlled pump unit
Each pump unit includes a pump metering drive assembly and pump head
assembly. The pamphlet assemblies both consist of two identical chambers,
pistons and seals, plus an active inlet valve and an outlet ball valve.
The channel flow outputs are initially joined by a low volume pre-mixer, and
are then connected by a capillary coil to a pressure pulse damper. The
pressure pulse damper also serves as a pressure transducer, which sends
system pressure information to the user interface.
This output flow, called primary flow, is connected to the Electronic Flow
Control (EFC) system. The EFC system consists of an Electro-Magnetic
Proportioning Valve (EMPV) in series with a Flow Sensor. The EMPV is
protected from particles in the mobile phase by a solvent filter frit.
Responding to user-entered column flow setpoint, the EFC system determines
how much of the main flow volume is ultimately delivered to the column. The
remaining main flow volume, which is not required by the column, is diverted
to waste by the EMPV.
Under user control, the EMPV can also function as a purge valve, for purposes
of solvent changeover, etc. In this case, the EMPV is totally open, and the total
main flow is diverted to waste.