Chapter 2 13
Description of Components
Detector Cap serves to provide an attachment for the ignitor assembly and pro-
vides the path to the exhaust vent.
Flame Arrestor prevents the flame from propagating out through the vent.
Gas Lines are connected to the detector base. The lower gas line (COMB) pro-
vides the hydrogen-rich combustor gas that sweeps out the combustor base. The
upper gas line (WALL) provides an oxygen-rich gas mixture that sweeps out the
region between the detector body and the combustor, and provides gas to the
ignitor.
Heater Cable Assembly allows the host GC to control the temperature of the
PFPD sensor assembly.
Ignitor Assembly threads onto the detector cap’s ignitor tube.
Light Pipe is a quartz rod specifically designed for optimal transmission of the
chemiluminescence to the PMT.
Light Pipe Clamp compresses the light pipe O-ring, which provides a gastight
seal between the light pipe and the detector body.
Mounting Plate attaches the PFPD assembly to the top of the GC oven using
mounting screws.
Optical Filter mounts inside the PMT housing. An O-ring is used to keep the filter
from moving and to ensure that all the light from the light pipe passes through the
optical filter. The filter spectrally isolates specific chemiluminescence.
Photomultiplier Tube (PMT) converts light energy into electrical current. Increas-
ing the voltage applied to the PMT increases the current generated by the PMT.
PMT Housing contains the optical filters, PMT, PMT socket, and the electronic
cables for the signal and high voltage of the PMT.
PMT Socket attaches to the PMT connector pins. Voltage supply to the PMT and
electrical responses to chemiluminescence (resulting from flame propagation
through the combustor) from the PMT are transmitted through these pins.
Viton O-ring provides a light-tight seal between the PFPD detector body and the
PMT housing-filter assembly, and it prevents movement of the optical filter, light
leakage around the optical filter, and provides a “soft” bottoming to the PMT. The
Viton O-ring around the light pipe holds the light pipe in place when the light pipe
clamp is tightened.
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