Inficon DataFID Portable Flame Ionization Detector for Lea Manual de usuario descargar pdf (Pagina 15)

074-578-P1A 15

Flame Ionization Detector Operation

The DataFID uses a flame ionization detector for the measurement of combustible organic compounds in

air at parts-per million levels. The permanent air gases (argon, carbon dioxide, nitrogen, oxygen, water

vapor, etc.) are not ionized by the flame and thus are not measured.

When the DataFID is flamed on, the internal pump draws air in through the DataFID inlet. This sample air

provides the oxygen necessary for combustion in the hydrogen fed flame.

Figure 1:. Flame Ionization Detector

When the proper ratio of hydrogen to air is present in the combustion chamber, the flame is started

automatically with a glow plug. A thermocouple is used to monitor the status of the flame.

When the sample passes through the flame, the combustible organic compounds in the sample will be

ionized. After the compounds have been ionized by the flame, the ionized particles are subjected to a

continuous electric field between the repeller electrode at the jet (+75V) 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 ionization chamber. An electrometer circuit converts the current to a voltage that

is then fed to the microprocessor.

After the sample passes through the flame and has become ionized, it is vented from the detector through

a flame arrestor, also known as exhaust frit. The flame arrestor prevents the flame from igniting any

flammable gases present in the sampling location.

Electrometer

Repeller Electrode

(Jet +75 Volts)

Collector Electrode

Sample In

Exhaust Out

Flame Arrestor

Microprocessor

Combustion Chamber

Glow PlugThermocouple

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Inficon DataFID Portable Flame Ionization Detector for Lea Manual de usuario Pagina 15