The working principle of zirconia oxygen sensor:
The zirconia oxygen sensor is designed using the oxygen ion conductivity of stable zirconia ceramics in an environment above 650°C. Under certain temperature conditions, if there are different partial pressures of oxygen (ie oxygen concentration) in the gas on both sides of the zirconia bulk ceramic, a series of reactions will occur inside the zirconia ceramic, and oxygen ions Migration. At this time, through the lead electrodes on both sides of the zirconium dioxide, a stable millivolt level signal can be measured, which we call the oxygen potential. It obeys the Nernst equation: where E is the oxygen potential (mv) output by the oxygen sensor, Tk is the absolute temperature (K) in the furnace, and P1 and P2 are the oxygen partial pressures of the gas on both sides of the zirconium dioxide. . In practical applications, one side of the zirconium dioxide is introduced into a gas with a known oxygen concentration (usually air), which we call the reference gas. On the other side is the gas to be measured, which is the atmosphere in the furnace that we want to detect. The signal output by the oxygen sensor is the oxygen potential signal. Through the Nernst equation, we can get the relationship between the oxygen partial pressure and the oxygen potential in the atmosphere of the measured furnace. When the reference gas is air, it can be expressed as: where E is the output oxygen potential of the oxygen sensor; Tk is the absolute temperature in the furnace; P02 is the partial pressure of oxygen in the furnace. Our oxygen sensor products are equipped with a self-heating device, and the general temperature is guaranteed to be 700 ℃, so that the TK value is basically constant, so that the oxygen partial pressure concentration in the furnace can be directly measured by the above formula. In engineering applications, standard gases are used to calibrate the corresponding relationship between the oxygen sensor output oxygen potential E and the oxygen partial pressure concentration PO2. This method is also recognized as the most accurate and direct calibration method.
The direct measurement output of the zirconia oxygen sensor is the difference between the concentration of the measured atmosphere and the standard air difference potential value, which we call the oxygen potential. When the potential value is at the zero point (that is, the air measurement), there is a deviation in the initial output potential of different probes. There may also be errors when the output potential is converted by the model to output the oxygen concentration. Therefore, it is necessary to calibrate the probe signal in the oxygen analyzer, otherwise there will be a large deviation between the displayed oxygen concentration and the actual oxygen concentration of the measured atmosphere. , Can not meet the needs of on-site production, and even mislead the control to affect production.
When modifying parameters, you can refer to the theoretical values provided in the last attached table (the table is a purely theoretical calculation value, and deviations should be considered in the project), and the measurement system should be adjusted corresponding to the actual project. The specific correction is generally carried out by standard gas calibration. The method is to pass the standard gas confirmed by the measurement verification into the probe through the standard gas port, and measure the output oxygen potential and the oxygen concentration displayed by the meter. The oxygen concentration displayed by the meter should be the same as that of the standard gas. Deviation is to correct the linear parameters of the instrument; the standard measurement requires the use of at least three different standard gas calibration systems, so that the linearity of the system is corrected after three calibrations to ensure the normal operation of the system.
Under certain temperature conditions, if the partial pressure of oxygen on both sides of the zirconia bulk ceramic is different, the inside of the zirconia ceramic will change. At this time, through the two terminals, a stable millivolt level signal can be measured, which we call the oxygen potential.
It obeys the Nernst equation: where E is the oxygen potential (mv) output by the oxygen sensor, Tk is the absolute temperature (K) in the furnace, and P1 and P2 are the oxygen partial pressures of the gas on both sides of the zirconium dioxide. In actual application, one side of the zirconium dioxide is passed into a gas with a known oxygen concentration, which we call the reference gas.
The other side is the measured gas, which is the atmosphere in the furnace we want to detect. The signal output by the oxygen sensor is the oxygen potential signal. Through the Nernst equation, we can get the oxygen partial pressure and oxygen potential in the atmosphere of the measured furnace. Relationship. When the reference gas is air, it can be expressed as: where E is the output oxygen potential of the oxygen sensor; Tk is the absolute temperature in the furnace; P02 is the partial pressure of oxygen in the furnace. The oxygen sensor products of Wuhan Huamin have a self-heating device, and the temperature is generally guaranteed to be 700 ℃, so that the TK value is basically constant, so that the oxygen partial pressure concentration in the furnace can be directly measured by the above formula.
In engineering applications, standard gases are used to calibrate the corresponding relationship between the oxygen sensor output oxygen potential E and the oxygen partial pressure concentration PO2, which is currently the most commonly used method.
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