Oxygen measurement

Oxygen analyser usage examples.

Optimization of gas and oil burners.

Gas and oil burners are used for heating houses, offices, hospitals, greenhouses and so on. For optimal combustion efficiency of the burner it is important the heat from the burner is transferred efficiently to the water or oil or other fluid used to transfer the heat. This fluid is used to distribute the heat in to the building, greenhouse etc. The oxygen concentration in the exhaust gas of the burner is an important figure for the efficiency of the burner. It will tell if the burner is rich or lean on fuel. With the use of an oxygen measurement device the burner can be monitored for optimal efficiency. Also O2 analyser based control systems can be used to automatically adjust the air fuel ratio from the burner to changing weather conditions. The automatic adjustment improves the combustion efficiency of the burner. This will lower the fuel consumption and provide financial savings.

Control and monitoring of Inert gas systems.

When gasoline, diesel, oil or other fluids are stored in tanks, above the fluid will form a vapor consisting of the fluid and the surrounding air. (usually oxygen) One can imagine that a mix of gasoline vapor and oxygen is very flammable. By replacing the oxygen with blanketing gas (Nitrogen or Carbon Dioxide are commonly used gasses for this purpose) or flue gas with a low concentration of oxygen, the danger is eliminated. It is important to make sure the oxygen content in the blanketing gas is below the explosion limit. The O2 sensor is used to measure oxygen concentration in the inert gas to guarantee the explosion risk is eliminated because low oxygen concentration is present.

Packaging of fresh food

Fresh food will stay fresh longer when it is packed with packaging gas. Depending what food this can be oxygen free gas. N2 and CO2 are used for this purpose. To make sure the packaged food is filled with the oxygen free gas the O2 content of the gas in the package is measured with an O2 sensor.

Welding and metallurgic applications.

When Metals are welded or melted heat must be applied. When the metals are heated deterioration due to oxygen can occur. To prevent this deterioration the oxygen has to be replaced with noble gas such as Argon and Helium. The O2 analyser is used to monitor when sufficient noble gas is present to prevent spilling of the gas.

Environmental monitoring of incinerators and crematory.

Environmental laws require monitoring of exhaust gas of incinerators for emission control. Sufficient oxygen in the exhaust gas will guarantee complete and clean burning of the waste and limit exhaust emissions. Therefore exhaust gas of incinerators need to have an oxygen concentration of 3-6% (Depending on type of incinerator and waste. Please check with local environmental laws) The oxygen analyser is used to measure the oxygen content and prevent rich mixtures. With the analogue output the measured oxygen signal is lead to a recorder which will save the measured oxygen content among other parameters as required by the environmental laws.

Measuring principle of the O2 sensor.

The O2 content is measured by the sensor and transferred to the O2 control unit. The O2 control unit is used to transfer the signal and display the value. The signal is also scaled to 4-20 mA outputs. The sensor is heated to approx 750 degrees celsius for normal operation. The sensor consist of 4 main parts. Pumpingcel (3), nernstcel (4) heater (5) and diffusion-chamber (6). The sample gas enters the diffusion chamber. Based on the difference in oxygen content of the gas in the reference chamber (2) and diffusion chamber (6) a voltage is generated. When the oxygen content of both chambers is equal the generated voltage is 450 mV. The output of the differential amplifier (7) is zero in this situation. When the oxygen content is not equal O2 molecules are added or removed by the pumping cell (3) In this situation the output of the differential amplifier will trigger the PID controller to adjust the pumping cell (3) The oxygen content is adjusted until the O2 measured on both sides is balanced. The current to the pumping cell is a measured and from this signal the O2 content is calculated by the control unit and indicated on the display (9).