Description of Design
26
Description of Design
The Dräger PIR 3000 infrared gas transmitter is a gas transmitter designed to
determine the concentration of gases and vapours in the ambient air. The principle
of measurement is based on the concentration-dependent absorption of infrared
radiation in measured gases.
The monitored ambient air diffuses through sintered material into the flameproof
housing of a measuring cuvette. The broadband light emitted by the radiator
passes through the gas in the cuvette and is reflected by the cuvette walls from
where it is directed towards the inlet window of a dual element detector. One
channel of the detector measures the gas-dependent light transmission of the
cuvette (measuring channel), the other channel is used as reference. The ratio
between measuring and reference signal is used to determine the gas
concentration in the cuvette. The cuvette is heated to avoid condensation of the
atmosphere's moisture content.
Internal electronics and software are used to calculate the concentration. The gas
transmitter sends a standard 4 to 20 mA output signal.
Due to its robust design and the measuring method, the gas transmitter has long
maintenance and calibration intervals (see "Maintenance" on page 20). A gas
sensitivity drift is very unlikely due to the infrared-optical principle of measurement
and in addition, the zero point stability is enhanced by an automatic tracking
system.
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