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1. Why cannot a zirconia oxygen analyzer be calibrated immediately after it is put into use? Answer: This is because the readings are abnormal within 24 hours of the chiller being put into operation; calibration is performed using standard gas after one day of operation. This is because cold detectors or newly installed detectors contain some moisture or flammable substances. After being heated, these absorbed waters evaporate and the flammable substances burn, consuming the reference air in the reference-side battery. As a result, the oxygen content of the reference air falls below the normal value of 20.6%, which leads to lower detector signals or even negative signals. This in turn causes the measured oxygen content to be higher than 20.6%, and such measurements are inaccurate. Accurate measurements can only be obtained after the moisture and flammable substances inside the detector have been completely replaced by fresh air. Therefore, a zirconia oxygen analyzer requires at least one day of operation of the heating unit to be calibrated. 2. Why is it necessary to calibrate the zirconia oxygen analyzer regularly? Answer: There are many interference factors during the use of zirconia oxygen analyzers, such as the aging of the zirconium tube, dust accumulation, and the corrosion of the electrodes by SO2 and SO3. After operating for a period of time, the performance of the instrument gradually changes, which introduces errors in measurements; therefore, it is necessary to calibrate the zirconia oxygen analyzer regularly! The calibration cycle is usually 1–3 months, depending on the operating environment and usage conditions of the zirconia oxygen analyzer. During calibration, pure N2 cannot be used as the zero gas; typically, the zero gas should be 10% of the full scale ； The range gas is 90% of full scale ； The zirconia oxygen analyzer uses dry air as the span gas in the field ； For the zero gas, 100PPM O2 is used. This is because at levels below 100PPM at zero, the error associated with the standard gas has a significant impact on the zirconia oxygen analyzer, and the calibration purge time is too long; moreover, it is difficult to achieve an accurate level of purification ； The measured values use the extended line of measurement linearity. Practice has proven that Changhui Instrument Manufacturing Co., Ltd.’s choice was clear and effective! 3. Why should a zirconia oxygen analyzer not be turned on and off casually? Answer: There are two reasons: First, since the zirconia tube is a ceramic tube, it does have a certain degree of resistance to thermal shock, but during shutdown processes, sudden changes in temperature due to rapid cooling or heating can cause the zirconia tube to break. Therefore, it is best to avoid unnecessary shutdown operations ； Secondly, the thermal expansion coefficients of the platinum electrode coated on the zirconium tube and the zirconia tube are not identical; after being in use for a period of time, this can lead to detachment during start-up and shutdown processes, resulting in an increase in the internal resistance of the probe and even damage to the detector. Be cautious when shutting down! http://yunrun.com.cn/upload/201805/10/201805101749560195.png Zirconia oxygen analyzer yunrun.com.cn/tech/1965.html 4. How to determine the constant temperature of a zirconia detector? Answer: Enter the menu and check whether the detector temperature matches the voltage; this helps determine whether the heating and temperature control systems are functioning properly. When the detector temperature is much higher than the constant temperature, it indicates that the thermocouple is open-circuited. Since the converter is equipped with a open-circuit protection circuit, once the thermocouple breaks, it generates a millivolt signal in place of the thermocouple signal, causing the temperature displayed by the detector to be higher. This also triggers the shutdown of the heating power supply to prevent the detector from being damaged. At this time, although the temperature is extremely high, the electric furnace is actually not heating; this can be confirmed by measuring the resistance across the thermocouple (with its leads disconnected), as the normal resistance of a thermocouple should be less than 20 ohms. If a check reveals that the temperature is below the set value, this should prompt consideration of insufficient heating, a broken heating wire, or faults and damages to the temperature control system. 5. What should be done if the reading of the zirconia oxygen analyzer is too high? Answer: Ignoring the previous factors, the first thing to consider is air leakage at the detector inlet ； The zirconia oxygen analyzer has not been calibrated for a long time or has been improperly calibrated. 6. What should be done if the reading of the zirconia oxygen analyzer is too low? Answer: The zirconia oxygen analyzer indicates calibration or requires calibration ； The sample gas contains flammable gases ； High back pressure in the vent line ； 7. What should be done if the measurement values of a zirconia oxygen analyzer fluctuate greatly? Answer: The zirconia detector is aging, with high internal resistance and poor electrode contact ； If the sample gas contains high humidity or water droplets, it vaporizes inside the detector ； 8. What to do if there is extreme drift in the measurement values of a zirconia oxygen analyzer and the signal exceeds the range? Answer: There are component damages in the zirconia detector, such as broken zirconia tubes, open circuits in electrode leads, detector aging, and broken temperature compensation resistors (oxygen content: 100%) ； http://yunrun.com.cn/upload/201805/10/201805101752455016.png 9. What are the causes and symptoms of aging in zirconia probes? Answer: What we usually mean by probe aging refers to the aging of the zirconia detector, which is primarily manifested in two aspects: an increase in internal resistance and an increase in background potential. ① Increase in internal resistance: In practical use, it is the increase in internal resistance caused by probe aging that is most noticeable. Internal resistance refers to the input resistance between the two ends of the signal line; it is the sum of the lead resistance, the interface resistance between the electrode and zirconia, and the volume resistance of zirconia. Therefore, electrode evaporation, electrode detachment, and the destabilization of the zirconia electrolyte (the transformation from stable zirconia to unstable zirconia) can all cause an increase in internal resistance. By measuring the internal resistance of the detector, its aging condition can be determined. Based on experience, when the internal resistance increases to near its operational limit, large fluctuations in the signal occur, and some systems exhibit delayed responses. For these detectors, the background potential is not necessarily very high. ②The background potential increases. The background potential is the additional potential of the battery. There are two factors that cause an increase in the background potential: one is a permanent factor associated with the battery itself, such as the corrosive effects of SO2 and SO3 as well as battery asymmetry ； Another type consists of temporary factors, such as electrode dust and poor air convection; once these conditions improve, the background potential can be reduced. An increase in the background potential often reflects the degree of aging of the detector; when the E0 value exceeds the maximum adjustable range of the zirconia oxygen analyzer, it indicates that the detector is damaged. For example: a zirconia material has an E0 value of -5mV at the time of production, with an allowable range of 0 to -30mV; after being used for half a year, its value becomes -13mV ； After 18 months of use, it becomes: -29mV ； This situation indicates that the detector has aged and needs to be replaced. It should be noted that the aging of some detectors is manifested as an increase in the background potential, while some detectors show no such phenomenon despite aging; therefore, we need to analyze this carefully. When the increase in the background potential is caused by temporary factors, over time it is possible for the background potential to first increase and then decrease. The number of probes that age due to an increase in the background potential is smaller than the number that age due to an increase in internal resistance; a mere increase in the background level generally does not result in significant fluctuations in the signal. 10. What precautions should be taken when using a zirconia oxygen analyzer? ①It is necessary to control the pressure of the sample gas; generally, the pressure in a zirconia oxygen analyzer should not exceed 0.05 MPa ； ②The output pressure of the gauge gas secondary meter shall not exceed 0.30 MPa ； ③All gas lines that lead into the zirconia oxygen analyzer must undergo thorough leak testing; even minor leaks can allow oxygen from the ambient air to penetrate, resulting in higher measurement values. Although the pressure of the sample gas is higher than the ambient pressure during measurement, the oxygen content in the sample gas is at a trace level. According to Faraday’s law, the partial pressure of oxygen is proportional to its volume fraction. The atmosphere contains about 21% oxygen, which is roughly ten thousand times higher than the partial pressure of oxygen in the sample gas, expressed in PPM. Therefore, the partial pressure of the trace amount of oxygen in the gas sample is much lower than that in the atmosphere. When a leak occurs, oxygen from the atmosphere will quickly diffuse in through the leak site. Also, the sampling pipeline should be as short as possible, with as few joints as feasible. It is essential to ensure that the joints and valves are properly sealed, and a leak test should be conducted after the pipeline connections are completed. Requirements for airtightness testing: At a test pressure of 0.25 MPa, over a period of 30 minutes, the pressure drop should not exceed 0.01 MPa. During normal operation of the instrument, a systematic leak check must also be carried out every six months. ④The pipeline material is preferably copper or stainless steel pipes, with polytetrafluoroethylene pipes as a secondary option. Lubricated rubber hoses, white glue hoses, and similar types of tubes should be avoided, as their airtightness and material resistance to permeation are too poor, resulting in large errors when measuring trace amounts of oxygen at standard measurement pressures. The outer diameter of the pipeline is usually chosen to be 6 millimeters or 1/4 IN; 3 millimeters or 1/8 IN is also an option. In any case, stainless steel pipes are preferred. These pipes need to be cleaned and degreased to keep their inner walls smooth and clean. For the analysis of oxygen at trace levels (<1PPMV), stainless steel pipes with polished inner walls should be used. The dead volume of the selected valves, fittings, should be as small as possible. ⑤Regularly clean the fan filter of the zirconia oxygen analyzer, once per quarter ； The environment is harsh, requiring regular cleaning to prevent the instruments from overheating due to poor ventilation ； ⑥The installation location of the zirconia oxygen analyzer should be level and away from sources of vibration ； To prevent errors caused by uneven sample convection resulting from the detector not being level ； ⑦The environment surrounding the zirconia oxygen analyzer should have good ventilation; enclosed spaces must be avoided, as measurement errors can occur due to uneven oxygen levels ； ⑧To prevent moisture in the sample from condensing on the tube walls, thereby affecting the dissolution and absorption of trace oxygen, insulation or heating measures should be applied to the sampling pipeline as appropriate. When detecting trace amounts of oxygen in liquid nitrogen, special attention must be paid to heating measures; otherwise, since the boiling point of oxygen is 13 degrees lower than that of nitrogen, uneven vaporization of the sample gas will result in significantly low measurement values. ⑨Before entering the zirconia oxygen analyzer via the gas line, it must pass through a physical filter with a precision of 10u ； If air resistance is detected, check the filter screen (filter) first ； When measuring gases containing corrosive substances, activated carbon filtration should be used first. ⑩To prevent moisture in the sample from condensing on the tube walls, thereby affecting the dissolution and absorption of trace oxygen, insulation or heating measures should be applied to the sampling pipeline as appropriate. When detecting trace amounts of oxygen in liquid nitrogen, special attention must be paid to heating measures; otherwise, since the boiling point of oxygen is 13°C lower than that of nitrogen, uneven vaporization of the sample gas will result in significantly low measurement values. ⑪In principle, the measurement location of a trace oxygen analyzer should be as close as possible to the measuring unit, in order to avoid long pipelines and excessive sources of uncertainty that could affect the reliability of the measurement data. ⑫The sample gas must not contain oily components or solid particles, to prevent clogging and contamination of the permeation membrane. ⑬The sample gas should not contain sulfides, phosphides, or acidic gases. These components can cause damage to fuel cells, especially alkaline fuel cells. ⑭Since the detection is carried out at high temperatures, if the gas to be tested contains H2, CO, and CH4, these substances will react with oxygen, consuming some of it and reducing the oxygen concentration, which leads to measurement errors. Therefore, when using a zirconia oxygen analyzer to measure gases containing flammable substances, this factor should be taken into account to avoid inaccurate measurements.