340 Electron Capture Detector (ECD)
Theory of operation
2 of 24
Jun 2001
Detectors
Agilent 6890 Gas Chromatograph Service Manual
EPC detector
The EPC version of the ECD detector has one flow line for the anode purge/
makeup gas. After an initial filter frit, it splits into two paths. Each line has
a proportional valve controlled by a pressure sensor, and a non-adjustable
restrictor frit. The makeup gas line sweeps past the end of the column and
carries the column effluent into the ECD cell. The anode purge flow sweeps
the upper part of the ECD and cleans sample deposition from the detector.
Figure 340-2 EPC ECD flow diagram
Manually controlled detector
The manually controlled ECD has a pneumatic supply line for the anode purge
gas and for the makeup gas. Both lines have an on/off solenoid valve and a
nonadjustable restrictor frit. A pressure regulator allows for adjusting the
Filter
frit
Proportional
valves
Pressure
sensors
Restrictors
Vent
Capillary adapter
63
Ni plating
Makeup
PS
PS
Anode
purge
Anode
purge and
makeup gas
in
Pressure
control loops
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