Emerson X-STREAM XE User Manual

Emerson Process Management GmbH & Co. OHG 3-5
X-STREAM XE
Instruction Manual
HASXEE-IM-HS
10/2012
3
Measuring Principles
3.2 Oxygen Measurement
3.2 Oxygen Measurement
Three different principles are used for measu-
ring oxygen concentrations. The principle
used in your specic instrument is given by the
channel code (sample gas designator) on the
nameplate label ( gure on page 2-22):
pO
2
= paramagnetic sensor
eO
2
= electrochemical sensor
tO
2
= trace oxygen sensor
3.2.1 Paramagnetic Measurement
Fig. 3-4: Paramagnetic Oxygen Sensor -
Assembly Principle
1 Permanent magnet
2 Platinum wire
3 Mirror
4 Glass ball
5 Loop
6 Photodetector
7 Light source
8 Preamplier
9 Display
10 Gas inlet
11 Gas outlet
4 1 5 3 6 8
11 7 9
2
10
This oxygen measurement principle is based
on the paramagnetic characteristic of oxygen
molecules:
Two cavernous glass spheres lled with nitro-
gen are arranged in a dumb¬bell conguration.
This dumbbell with a platinum wire is mounted
rotatable inside a strong inhomogeneous ma-
gnetic eld. A small mirror is xed on the front
side of the dumbbell, which reects light from a
light source towards two photo detectors (Fig.
3-4). The dumbbell is surrounded by another
platinum wire, which is bent like a coil around
each glass sphere. It generates a magnetic
eld when supplied by an electric current to
control the dumpbell´s deection.
Oxygen molecules within the sample gas
are attracted be the magnetic eld due to
their paramagnetic characteristic and will
be concentrated into the area of the highest
eld strength in the inhomogeneous eld.
In doing so they displace the nitrogen lled
glass spheres. This generates a torque on
the dumbbell which depends on the oxygen
concentration in the sample gas. The dumbbell
starts to rotate and the light reected by the
mirror on the dumbbell generates a signal on
one of the two photo detectors. Initiated by the
photo detector signal a preamplier drives a
current through the platinum wire surrounding
the dumbbell. This generates a compensating
magnetic eld and rotates the dumbbell back
into its zero position. The compensating cur-
rent gives a direct and linear measure for the
oxygen concentration within the sample gas.
The paramagnetic oxygen detector also
con¬tains a temperature sensor for compen-
sation and a heating ele¬ment to keep the
detector at approx. 55 °C.
Several variations are available including
corrosion resistant, solvent resistant and/or
intrinsically safe (for measuring ammable
gases) versions.

Emerson X-STREAM XE Specifications

General

Brand	Emerson
Model	X-STREAM XE
Category	Measuring Instruments
Language	English