Technical Implementation - Emerson Rosemount Xstream Series Instruction Manual

X-STREAM
The detector is filled with the gas to be
measured and therefore sensitive to the related
characteristic wavelength band only.
The absorption chamber is sealed with a
window transparent for IR radiation [CaF
(Calziumfluorid)] .
There is no absorption when the IR(UV)
radiation passes the reference side of the
analysis cell , so the intensityis at a maximum
when it arrives at the detector. The gas within
the detector is heated, therefore expands and
flows from absorption chamber through flow
channel to the compensation chamber. This
flow generates a voltage signal.
When the IR(UV) radiation passes the sample
side of the analysis cell, part of it is absorbed
by the sample gas decreasing the radiation
intensity. As an effect the gas within the detector
cools down and flows from the compensatoin
chamber back into the absorption chamber.
This flow again causes a voltage signal by the
micro flow detector which is now reverse to the
previous signal.
So the micro flow detector generates alterna-
ting signals. The flow channel is designed to
not influence the gas flow and therefore the
change in signal is proportional to the change
in radiation intensity which is proportional to
the concentration of gas to be measured.
The flow detector signal is passed to elec-
tronics conditioning the signal and converting
it into a usefull format.
3-4
3-1 Infrared (IR) and Ultraviolet (UV) Measurement
3-1-3

Technical Implementation

The broadband IR (UV) radiation emitted by a
special source passes a chopper wheel (fig.
3-3 showing a dual channel analyzer). In case
of IFC principle it passes additional optical
filters, before entering the analysis cell. The
2
radiation leaving the cell is focused to the
detector by means of a filter cell. The detector
output signal is passed to micro processor
controlled electronics conditioning and
converting it to reasonable units (Vol-%, ppm,
mg/m³, etc.) shown on the alphanumeric
display.
Depending on gas component and measuring
range several photometer designs are used
with X-STREAM series analyzers, differing in
analysis cell length, kind of detector and used
filters. Optionally the assemby may be sealed
against ambience: O-rings between the
components prevent ambient air to come in the
optical path and interfere the measurement.
The photometer assembly is mounted on the
BKS main board, which itself is placed in
housings rail.
Emerson Process Management GmbH & Co. OHG
Instruction Manual
HASAxE-IM-HS
05/2006