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Oxygen Analyzers
Because of the wide verity of applications our oxygen analyzer systems vary depending on your needs. Choosing a system will depend on the process temperature, the speed of response to a change in the process gas and depth of the insertion desired.
Click here to find out How the measurement is made and How the cell works.
Model 1401 - Basic Heavy Duty In-Situ oxygen analyzer...
Model 1402 - More features Heavy Duty In-Situ oxygen analyzer...
The EMS oxygen analyzers are designed to measure the percent of oxygen concentration in an environmental state which exists in combustion furnaces and/ or in associated flues. The system uses the fuel cell sensor principle for development of a DC voltage potential across a zirconium cell for variations in percentage of oxygen content in accordance with the Nernst Equation:
The fuel cell sensor is surrounded by a cylindrical heater. The cell is heated to 1499° F (815° C) +10° . A flat RTD temperature sensor measures the effective cell temperature, and the resulting RTD resistance is fed to a controller. The temperature controller action relative to the cell RTD temperature (RTD resistance) and a fixed set point resistance, control the heater current to the value required to keep the cell at a constant temperature. Actual cell temperature is dependent on minor variations in heater-to-cell thermal flow efficiencies. Minor variations in this absolute cell temperature are to be expected from one probe to the next. Absolute temperature is not a critical function of the system.
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The oxygen analyzer cell consists of a ceramic tube made of yttria- stabilized zirconium oxide, with porous platinum electrodes, coated on both its inner and outer surfaces . When the cell is heated to a high temperature, above 1100° F (600° C), it becomes permeable to oxygen ions and vacancies in its crystal lattice permit the mobility of oxygen ions. In this way, the cell becomes an oxygen ion-conducting solid electrolyte. The platinum electrodes on each side of the cell provide a catalytic surface for the change of oxygen molecules to oxygen ions and oxygen ions to oxygen molecules. Oxygen molecules, on the high concentration reference gas side of the cell, gain electrons to become ions that enter the electrolyte. Simultaneously, at the other electrode, oxygen ions lose electrons and are released from the surface of the electrode as oxygen molecules. When the concentration of oxygen is different on each side of the cell, oxygen ions will migrate from the high oxygen concentration side to the low oxygen concentration side. This ion flow produces an electronic imbalance that results in a voltage potential between electrodes that is a function of the temperature of the cell and the ratio of oxygen partial pressures
( concentrations) on each side of the cell. The relationship between the oxygen concentration of the unknown gas, the oxygen concentration of the reference gas ( typically 20.95% oxygen by volume), and the temperature, voltage output, and cell constant of the fuel cell sensor is defined by the Nernst Equation. When the air is sampled the probe output is zero. At low oxygen concentrations (1% for example) , cell output is approximately 125 millivolts.
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