Specifications

DETECTOR METHODOLOGIES
Absorption chamber
Figure 2-2. Opto-Pneumatic Gas Detector
When the infrared radiation passes through the open measurement side of the analysis
cell into the detector, a part of it is absorbed depending on the gas concentration. The
gas in the absorption chamber is, therefore, heated less than in the case of radiation
coming from the reference side. Absorption chamber gas becomes cooler, gas
pressure in the absorption chamber is reduced and some gas from the compensation
chamber passes through the flow channel into the absorption chamber.
The flow channel geometry is designed in such a way that it hardly impedes the gas
flow by restriction. Due to the radiation of the chopper wheel, the different radiation
intensities lead to periodically repeated flow pulses within the detector.
The Microflow sensor evaluates these flow pulses and converts them into electrical
pulses which are processed into the corresponding analyzer output.
CaF
2
Window
Flow channel with
Microflow sensor
Compensation chamber
Rosemount Analytical µCEM Continuous Analyzer Transmitter 2–3