An oxygen analyzer is an instrument used to measure the concentration of oxygen in gases. The oxygen analysis method mainly determines the oxygen concentration based on gas detection techniques of different principles. Common oxygen analysis methods include:
1. Electrochemical method
Electrochemical oxygen analyzer is based on the principle of electrochemical reaction, using the reduction or oxidation reaction of oxygen on the electrode to generate current or voltage changes, thereby measuring the oxygen concentration in the gas.
Working Principle:
Electrochemical sensors typically consist of two electrodes (working electrode and reference electrode) and an electrolyte solution. When gas passes through the electrode, oxygen molecules undergo a reduction reaction on the working electrode, generating an electric current.
The intensity of this current is directly proportional to the concentration of oxygen, and by measuring the change in current, the concentration of oxygen in the gas can be accurately calculated.
Features:
High sensitivity, suitable for low concentration oxygen detection (such as environmental monitoring).
Fast response speed, suitable for real-time detection.
Suitable for measuring oxygen concentration in various gas mixture environments.
2. Thermal conductivity method (thermal conductivity method)
The thermal conductivity method measures oxygen concentration based on the different thermal conductivities of gases. The thermal conductivity of oxygen is different from other components in air such as nitrogen and carbon dioxide, and this principle is used for oxygen detection.
Working Principle:
The thermal conductivity sensor consists of two thermocouples and a heating element. Around the heating element, sensors will monitor the temperature changes of different gases based on their thermal conductivity differences.
The thermal conductivity of oxygen in air is different from other gases such as nitrogen and carbon dioxide, so the concentration of oxygen can be calculated by measuring the temperature changes of sensors.
Features:
Non consumable, no chemical reaction required, therefore the sensor has a longer lifespan.
Very sensitive to differences in thermal conductivity of gases, able to quickly measure oxygen concentration.
Suitable for gas environments with high oxygen concentration.
3. Resistance method (zirconia method)
The resistance method mainly measures oxygen concentration by reacting zirconia (ZrO2) ceramics with oxygen at high temperatures.
Working Principle:
Zirconia electrodes have conductivity to oxygen at high temperatures. When oxygen passes through zirconia material, oxygen molecules will adsorb and ionize on the surface of zirconia, generating a current signal.
The magnitude of the current signal is directly proportional to the concentration of oxygen.
This method is commonly used to measure high concentrations of oxygen, such as oxygen analysis during combustion processes.
Features:
Good high-temperature stability, suitable for oxygen analysis in high-temperature environments.
High precision, suitable for measuring oxygen concentration with high requirements.
It needs to be heated to a certain temperature, so the instrument starts slowly and consumes more energy.
4. Optical methods (UV absorption method, infrared absorption method)
The optical method utilizes the absorption characteristics of gases towards light of different wavelengths to measure oxygen concentration.
UV absorption method:
Oxygen has a specific absorption wavelength in the ultraviolet region, and the concentration of oxygen can be calculated based on the gas's absorption of ultraviolet light.
This method is suitable for detecting low concentration oxygen and is not affected by other gases.
Infrared absorption method:
Although oxygen itself absorbs less in the infrared region, infrared absorption method can be used to measure the relationship between oxygen concentration in gases and other gases (such as carbon dioxide, methane, etc.), and is usually used in combination with other gases.
Features:
High sensitivity and accuracy.
It will not be affected by interfering gases, but it has high requirements for equipment and is relatively complex.
Suitable for low concentration oxygen analysis.
5. Fourier Transform Infrared Spectroscopy (FTIR)
Fourier transform infrared spectroscopy utilizes the absorption characteristics of gases in infrared spectra to determine oxygen concentration through spectral analysis.
Working Principle:
Oxygen molecules absorb specific wavelengths of infrared radiation, and based on the intensity of gas absorption, Fourier transform technology is used to analyze the spectrum and measure the concentration of oxygen in the gas.
Features:
High precision, capable of analyzing multiple gases simultaneously.
The measurement of oxygen concentration is very accurate, but the equipment is complex and expensive.
6. Specific gravity method (fixed specific gravity method)
The specific gravity method calculates oxygen concentration by measuring the difference in specific gravity between oxygen and air.
Working Principle:
The specific gravity of oxygen is smaller than that of air. Based on this principle, the concentration of oxygen can be calculated by measuring the difference in specific gravity of gases.
Features:
Suitable for low concentration oxygen analysis, but with low sensitivity.
Commonly used for rapid detection of atmospheric oxygen concentration.