About The Fpd - Agilent Technologies 7820A Advanced User's Manual

5
Detectors

About the FPD

H
2
Frit
Valve
PS
Restrictor
PS = Pressure Sensor
102
The sample burns in a hydrogen-rich flame, where some species
are reduced and excited. The gas flow moves the excited species
to a cooler emission zone above the flame where they decay and
emit light. A narrow bandpass filter selects light unique to one
species, while a shield prevents intense carbon emission from
reaching the photomultiplier tube (PMT).
The light strikes a photosensitive surface in the PMT where a
light photon knocks loose an electron. The electron is amplified
inside the PMT for an overall gain of up to a million.
Makeup Air
Frit Frit
Valve Valve
PS
Restrictor
The current from the PMT is amplified and digitized by the FPD
electronics board. The signal is available either as a digital
signal on the communications output or as a voltage signal on
the analog output.
The FPD should not be stored at temperatures above 50 °C,
based on the original manufacturer's specifications for the PMT.
EPC Module
PS
Restrictor
Column
Vent
Emission Zone
Wavelength filter
Window
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