Emerson Rosemount 700XA Reference Manual page 21

Reference Manual
2-3-9000-744
Figure 1-8: µFPD PMT
A. µFPD PMT in the upper enclosure
The detection system in the µFPD uses the reactions of sulfur components in a
hydrogen/air flame as a source for analytical detection. The source of the µFPD's signal is
derived from the light produced by an excited molecule created in the flame's
combustion, that is, a photochemical process called chemiluminescence. A thermocouple
is fitted to the flame cell to ensure that the flame is present. If the flame is not detected,
the electrometer shuts off the hydrogen to the flame cell. It then supplies a voltage to the
igniter, waits five seconds, and opens the hydrogen shut off valve. The electrometer will
make between one and five ignition attempts if necessary. You can select the number of
ignition attempts on the Hardware → Detector screen. If the electrometer does not
succeed in igniting, then the GC shuts off the hydrogen, triggers an alarm, and waits for
attention from the operator.
Related information
Micro flame photometric detector (µFPD)
1.4.4 Micro flame photometric detector (µFPD) electronics
module
The electronics module contains two chambers. The internal chamber contains the photo
multiplier tube (PMT) to insulate it from outside temperature changes. The external
chamber is a thermo-electric cooler (TEC) controlled chamber, which houses the internal
chamber along with the electronic board that generates high voltage power through the
PMT.
Rosemount 700XA
Overview
June 2022
21