The analysis methods of trace oxygen mainly include colorimetry, chemical cell method, yellow phosphorus luminescence method, concentration cell method and gas chromatography. Among them, colorimetric method is an earlier analysis method, which is stipulated in national standards. Colorimetric analysis using copper ammonia solution is rarely used now, but it is still an arbitration method because of its complicated operation, difficult to ensure accuracy and unable to realize automatic on-line analysis. Yellow phosphorus luminescence method uses oxygen and yellow phosphorus for analysis, which has the characteristics of fast analysis and continuous analysis. However, the yellow phosphorus used in this method is a dangerous chemical, and the products produced are corrosive and have low detection limit, so it is rarely used now. Chemical cell method, concentration cell method and gas chromatography are mainly introduced. 1. The trace oxygen analyzer with chemical battery method refers to the analysis of trace oxygen by using the principle of redox battery. Its sensor (detector) is a chemical primary battery, which is mainly composed of a cathode, an anode and electrolyte. The above components are sealed in an inert housing. Oxygen in the gas to be measured enters O2 near the cathode of the battery to obtain electrons. The anode is made of metal lead, and the lost electrons themselves are oxidized. The electrons generated by the battery are extracted by the circuit and then compensated. The reaction formula is as follows: O2+2H2O+4e-→40H- cathode Pb+2OH-→pbo+H2O+2e. The total reaction formula 2pb+O2→2pbO can be divided into galvanic cell method, fuel cell method and Hertz cell method due to different realization methods. 2. Concentration battery method The concentration battery method, also known as zirconia battery method, takes zirconia as the key component of the detector, and forms an oxygen measuring battery with it as the main body, including a zirconia tube, a molybdenum electrode coated on the bottom of the tube and electrode leads, which can lead out signals; The heating furnace is used to heat the zirconia tube to keep it at the set temperature (78010℃); The standard gas pipe is used to connect the standard gas and the calibration probe; Thermocouple is used to measure the temperature in the oxygen battery and connected to the temperature control system of the transmitter; The terminal board is equipped with three pairs of terminals for signals, thermocouples and heating furnaces, as well as filters, mounting flanges and probe housings. As shown in figure 1, there are two platinum electrodes on the inner and outer surfaces of the bottom of the zirconia tube, namely the reference electrode and the measuring electrode, with two platinum wires respectively, to form a zirconia oxygen measuring battery, namely the oxygen concentration difference battery, and the reaction principle at the platinum electrode is O2+4e→ 2o2-; 2O2-→O2+4e, so that a potential difference is formed between the two electrodes, and a concentration battery (2) is formed. The main disadvantage of zirconia concentration battery is that reducing impurities has an influence on the analysis of trace oxygen. Because reducing substances can react with oxygen at 500-800 degrees Celsius, the consumption of oxygen makes the analysis result low. Its main advantages are wide measuring range, covering the analysis of constant to trace oxygen content, convenient use and long service life. 3. The advantage of gas chromatography in trace oxygen analysis is that it can detect many impurities at the same time. Because impurities in air separation gas are easy to separate, the configuration of chromatographic column system is simple. Chromatographic analysis is more suitable for detecting various impurities containing trace oxygen. The available chromatographic detectors mainly include thermal conductivity detector, electron capture detector, helium ionization detector, argon ionization detector, discharge ionization detector and atomic emission detector (AED). The disadvantage of chromatographic analysis of trace oxygen is that it can't realize real on-line analysis, that is, it can't monitor trace oxygen in real time, it needs intermittent detection, the equipment system is complex, and it needs carrier gas and auxiliary gas.