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Sample Out
Lampholder
UV Lamp
High Voltage
Plates
+125 Volts
Detector Cell
Sample In
Repeller Electrode
Figure 30
The ionized molecules in the detector cell are subjected to a
continuous electric field between the repeller electrode and the
collector electrode. The ions move in the electric field, generating a
current which is proportional to the concentration of the ionized
molecules in the detector cell. An electrometer circuit converts the
current to a voltage which is then fed to the microprocessor.
The UV lamp is operated by a high voltage lamp driver circuit which
delivers high voltage energy to the lamp through plates in the
lampholder. The lamp driver power supply is controlled by the
microprocessor based on a feedback signal from a light sensor on
the driver circuit board.
Lamp Power
Supply
Lamp Driver
Circuit
Microprocessor
Light Sensor
Electrometer
UV Lamp
UV Light
Collector Electrode
+
M
-
M
h ?
Ionized Molecule
+
+
e
M
M
M
Sample
M
Photoionization Detector
Technical Description
157
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Troubleshooting
