Specifications

Trace Oxygen Analyzer Module
Rosemount Analytical NGA 2000
748420-A
August 1999
1
I
NTRODUCTION
1
1.1 O
VERVIEW
This manual describes the Trace Oxygen (TO2) Analyzer Module of Rosemount Analytical's
NGA 2000 Series of gas analysis components.
The TO2 Analyzer Module is designed to continuously determine the concentration of trace
oxygen in a flowing gaseous mixture. The concentration is expressed in parts-per-million.
The TO2 Analyzer Module is configured as a shelf-mount module, designed to be installed
external from the platform on an associated shelf capable of holding two modules side-by-
side, with gas connections made from the rear. All electronics relative to sample detection
and conditioning are included in this module.
1.2 T
YPICAL
A
PPLICATIONS
The TO2 Analyzer Module has specific applications in the following areas:
•
Trace oxygen in product nitrogen and argon streams from air separation plants
•
Trace oxygen in inerting atmospheres for heat treat furnaces
•
Trace oxygen in glove-box applications
1.3 T
HEORY OF
T
ECHNOLOGY
The TO2 Analyzer Module uses the coulometric principle of oxygen detection. This
technology is based on the fact that oxygen in the sample is reduced by an electrochemical
reaction. This reduction occurs at the cathode and results in the generation of hydroxyl
ions. These hydroxyl ions migrate to the anode where they are oxidized to reform oxygen.
The oxidation reaction generates four electrons which in turn migrate to the anode to
participate in the reduction reaction:
(Cathode Reaction)
O
2
+ 2 H
2
O + 4 e
-
→
4 OH
-
(Anode Reaction)
4 OH
-
→
O2 + 2 H
2
O + 4 e
-
A polarizing voltage of approximately 1.3 VDC is applied between the anode and cathode
to drive the oxidation and reduction reactions. The resulting current flow produced by the
flow of electrons is directly proportional to the oxygen content in the sample gas.