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N96 Rosemount Analytical Inc. A Division of Emerson Process Management Preface P-5 Instruction Manual 748374-F March 2003 Model NGA2000 TO2 GLOSSARY OF TERMS Analyzer Module The module that contains all sensor/detector components for development of a Primary Variable signal; includes all signal conditioning and temperature control circuitry. Backplane The interconnect circuit board which the Controller Board, Power Supply, Analyzer Module power and network cables, I/O Modules and Expansion Modules plug into. Control Module The Operator Interface plus the Controller Board. Controller Board The computer board that serves as the Network Manager and operates the Display and Keypad. Distribution Assembly The Backplane and the card cages that hold I/O and Expansion Modules. Expansion Module A circuit board that plugs into the Backplane from the front of the Platform and performs special features not related to I/O functions. I/O Module A circuit board that plugs into the Backplane from the rear of the Platform. Has a connector terminal for communication with external data acquisition devices and provides an input/output function. Operator Interface The Display and Keyboard. Platform Any workable collection of the following: Controller Board, Power Supply, Distribution Assembly, Enclosure and Operator Interface. Power Supply Any of a variety of components that provides conditioned power to other NGA2000 components, from the Power Supply Board that plugs into the front of the Backplane in a stand-alone instrument to several larger ones that can power larger collections of modules and components. Primary Variable The measured species concentration value from an Analyzer Module. Secondary Variable Data placed on the network by a module regarding current status, e.g., sample flow, source voltage and other diagnostic information. System Any collection of Analyzer Module(s), Platform (s), I/O Module(s) and Expansion Module(s) P-6 Preface Rosemount Analytical Inc. A Division of Emerson Process Management Instruction Manual 748374-F Model NGA2000 TO2 March 2003 SECTION 1 DESCRIPTION AND SPECIFICATIONS 1-1 OVERVIEW This manual describes the Trace Oxygen (TO2) Analyzer Module of Rosemount Analytical's NGA2000 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-byside, with gas connections made from the rear. All electronics relative to sample detection and conditioning are included in this module. 1-2 TYPICAL APPLICATIONS 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 THEORY OF TECHNOLOGY 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) O2 + 2 H2O + 4 e-> 4 OH (Anode Reaction) 4 OH-> O2 + 2 H2O + 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. 1-4 FEATURES Among the features included in the TO2 Analyzer Module are: • Quick start feature • Electrolyte level alarm • High oxygen protection circuit with alarm • Sample flow indication. Rosemount Analytical Inc. A Division of Emerson Process Management Description and Specifications Instruction Manual 748374-F March 2003 Model NGA2000 TO2 ELECTRONICS SECONDARY ANODE (+) BI-STRATA™ DIFFUSION BARRIER SAMPLE IN SAMPLE OUT O2 SENSING CATHODE (-) SECONDARY CATHODE (-) O2 SENSING ANODE (-) O2 O2 e e KOH OH S S Figure 1-1. Trace Oxygen Detector Technology Description and Specifications Rosemount Analytical Inc. A Division of Emerson Process Management Instruction Manual 748374-F Model NGA2000 TO2 March 2003 Network/Power Module Computer Board Power Board Sensor Assembly Sensor Sample Flow Sensor Figure 1-2. Trace Oxygen Analyzer Module – Top View Rosemount Analytical Inc. A Division of Emerson Process Management Description and Specifications Instruction Manual 748374-F March 2003 Model NGA2000 TO2 1-5 SPECIFICATIONS a. General Measurement Species................... Trace Oxygen Ranges ............