I
NTRODUCTION
1-4
June 1997 Rosemount Analytical 748332-D
NGA Non-Dispersive Infraraed Analyzer
SAMPLE IN
SAMPLE
OUT
COMPONENT OF INTEREST
NON-INTERFERING COMPOUNDS
INFRARED
SOURCE
DETECTOR
REFERENCE
CELL
STATIONARY
PLATE
CHOPPER
SAMPLE
CELL
DIAPHRAGM,
DISTENDED
DIAPHRAGM,
DARK STATE
The detector is a "gas microphone" based on the Luft principle. The detector is
generally filled with the same gas being analyzed. The infrared energy is therefore
absorbed at the same wavelengths in the detector as that in the sample cell, making
the detector specific for the analyzed component. The detector converts the
difference in energy between sample and reference cells to a capacitance change.
This change, which is proportional to component concentration, is processed and
expressed as the primary variable on the network.
Other modules comprising the NGA 2000 unit then use this variable for a variety of
purposes (e.g., expressing the gas concentration on the Front Panel Display or
sending it to external data acquisition devices).
For a general understanding of the electrical interconnections in the NDIR Analyzer
Module, see Figure 2-5.
F
IGURE
1-2. NDIR T
ECHNOLOGY
1.4 SAMPLE REQUIREMENTS
Maximum allowable sample pressure is 690 hPa-gauge (10 psig) for a standard
configuration NDIR that has a flow restrictor which sets the flow at between 0.5 L/min.
to 1 L/min. Special high pressure cells (up to 10,350 hPa-gauge, 150 psig) are
available. Sample temperature range is 0
°
C to 55
°
C, and maximum dewpoint is 40
°
C.
The sample must be filtered to exclude particulates larger than 2 microns in size.
Consult factory for special configurations with specifications outside of those listed
above.
Содержание NGA 2000
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Страница 16: ...PREFACE P 10 June 1997 Rosemount Analytical 748332 D NGA Non Dispersive Infrared Analyzer NOTES ...
Страница 22: ...INTRODUCTION 1 6 June 1997 Rosemount Analytical 748332 D NGA Non Dispersive Infraraed Analyzer NOTES ...
Страница 54: ...REPLACEMENT PARTS 5 2 June 1997 Rosemount Analytical 748332 D NGA 2000 Non Dispersive Infrared Analyzer NOTES ...
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