For boilers, the oxygen content in the flue gas is a very important parameter, as it is a key indicator for judging the boiler's combustion status and efficiency. Up until now, with the development of science and technology, the common method for mastering and measuring the flue gas oxygen content in small and medium-sized boilers is to use zirconia sensors. We believe many users lack professional understanding of the measurement principle and usage considerations of zirconia sensors. Today, technical engineers from Anhui Tianfen Instrument Co., Ltd. will provide detailed explanations for the majority of zirconia users!

　　Analysis of Zirconia Sensor Measurement Principle

　　The basic principle of zirconia oxygen measurement is to utilize the so-called "oxygen concentration potential". That is, porous platinum electrodes are attached to both sides of a zirconia piece and kept at high temperature. If the oxygen content in the gases on both sides is different, oxygen ions will undergo "hole migration" on the electrodes. Since oxygen ions carry a 2-valent positive charge, an electromotive force will appear between the two electrodes. This electromotive force is generated due to the different oxygen concentrations of the gases on both sides of the solid electrolyte, hence it is called oxygen concentration potential, which can be calculated by the Nernst equation:

　　E=RT/4F×ln(P''O2/P'O2)

　　Where R is the gas constant, T is the thermodynamic temperature (K) of the cell, F is the Faraday constant, and P''O2/P'O2 is the oxygen partial pressure on both sides of the electrodes.

　　When one side of the solid electrolyte is air, the oxygen partial pressure on the other side of the solid electrolyte can be calculated from the electromotive force E output by the oxygen concentration cell. Therefore, when using a zirconia sensor, reference air needs to be introduced, which is also the measurement principle of a zirconia oxygen analyzer.

　　Curve Relationship Between Oxygen Concentration and Oxygen Concentration Difference Potential:

　　Analysis of Usage Considerations for Zirconia Sensors

　　1. Generally, zirconia sensors are divided into low-temperature and high-temperature types. We must remember not to mix them. Zirconia sensors for general boilers need to be high-temperature sensors.

　　2. Since zirconia sensors use precise electronic components internally, avoid installing them in places with severe vibration during use.

　　3. Do not install zirconia sensors in overly humid environments, and keep them away from corrosive substances.

　　4. It should be installed in the correct position, as shown in the figure below (for reference only).

　　5. Zirconia sensor accuracy drift and calibration.

　　During use, there are many interfering factors, such as the aging of the zirconia tube, ash accumulation, and corrosion of electrodes by SO2 and SO3. After operating for a period, zirconia sensors will experience accuracy drift, leading to measurement errors. Such measurement errors can cause operators or automatic control equipment to make incorrect judgments, which is very dangerous.

　　Therefore, it is advisable to use zirconia sensors with self-check functions, and the instrument must be calibrated regularly. The calibration cycle depends on the operating environment and usage conditions, typically around 1 to 3 months.

　　6. The working principle of zirconia oxygen sensors dictates that they must have standard atmosphere as reference gas. If a stable reference gas is not provided to the sensor, the detection accuracy will significantly decrease. Therefore, during use, it is essential to ensure the normal input of reference gas.

　　However, since zirconia sensors are made of ceramic materials, their molding process is complex and technical requirements are high, so it is still necessary to find professional zirconia manufacturers.

　　Another point worth noting is that the management of zirconia sensor usage is also very important, especially the self-check function and timely calibration. If a sensor without a self-check function is purchased and not calibrated in time, its accuracy will be greatly reduced.