200 Advanced Operation Manual
5 Detectors
About the FPD
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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.
The current from the PMT is amplified and digitized by the
FPD
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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
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should not be stored at temperatures above 50 °C,
based on the original manufacturer’s specifications for the
PMT.
Valve
Frit
Frit
Valve
PS = Pressure Sensor
Column
PS
PS
PS
Valve
Frit
Restrictor Restrictor
Restrictor
EPC Module
H
2
Air
Wavelength filter
Window
Vent
Makeup
Emission Zone
Transfer line
Restrictor
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