Fault diagnosis and treatment of zirconia analyzer

1.Why can't the instrument be checked immediately after being put into use?
Answer: This is because the indication is abnormal within 24 hours after the cold machine is put into operation, and the calibration is carried out by standard gas after being put into operation for one day. This is because there will be some adsorption water or combustible substances in the cold machine detector or the newly installed detector, after the heat machine, at high temperature, these adsorption water evaporation, combustible substances combustion, will consume the reference air in the reference side battery, leading the oxygen content of the reference air is lower than the normal value of 20.6%, there will be detector signal low, even negative signal, resulting in the measured oxygen content is higher, even more than 20.6% phenomenon, the measured value is not accurate. It is necessary to wait until the moisture and combustible matter inside the detector are replaced by fresh air to make the measurement accurate. Therefore, the zirconium oxide detector needs at least a heat engine for more than one day to be calibrated.
2.Why do you need to calibrate the analyzer periodically?
A: There are many interference factors in the process of using zirconia analyzer, such as aging of zirconium tube, deposition of ash, corrosion of SO2 and SO3 to electrode, etc. After a period of operation, the performance of the instrument will gradually change, bring errors to the measurement, so the instrument must be calibrated regularly! The calibration period is usually 1-3 months, depending on the environment and usage of the instrument.
When calibrating, pure N2 can not be used as zero gas, usually the zero gas should be 10% of the full range; The measuring gas is 90% of the full measuring range; BYG site uses dry air as the measure gas; Zero-point gas is 100PPMO2, which is considered that the zero-point 100PPM or below, the standard gas error has too much influence on the instrument, and the check cleaning time is too long, and not easy to blow in place; The measured value uses a linear down line. Practice has proved that our choice is clear and effective!
3.Why don't you switch the instrument often?
A: There are two reasons: First, because the zirconia tube is a ceramic tube, although there is a certain degree of thermal shock resistance, but in the process of shutdown, because of the rapid cooling, rapid heating and isothermal increase may lead to the rupture of the zirconia tube, therefore, it is better to do less unnecessary shutdown operation; The second is that the thermal expansion coefficient between the platinum electrode coated on the zirconium tube and the zirconium tube is inconsistent, and after a period of use, the phenomenon of falling off is easy to occur in the process of opening and closing, leading to the increase of the inner resistance of the probe and even damaging the detector. Be careful with downtime!
4.Determination of detector constant temperature
A: Entering the menu to check for consistency between the detector temperature and the voltage helps to determine if the heating and temperature control system is normal. When the detector temperature is much higher than the constant temperature, the thermocouple is broken. Because the converter is provided with a break-couple protection circuit, once the thermocouple is broken, it will generate a millivolt signal instead of the thermocouple signal, so that the temperature of the detector is higher, and the heating power is broken to protect the detector from burning. At this time, although the temperature is very high, in fact the electric furnace is not heated, the measurement of the resistance at both ends of the thermocouple (the lead must be disconnected) can confirm this, the normal resistance of the thermocouple should be less than 20 ohm.
If it is found that the temperature is below a constant value, it should be considered that the heating is not performed or the heating wire is broken or the temperature control system fails and is damaged.
5.High measurement
Before the factors are not considered, the first thing is to consider the leakage of detector inlet; The instrument has not been calibrated for a long time or has not been calibrated properly.
6.Low measurement
Instrumentation calibration or calibration required.
The sample gas contains combustible gas.
The back pressure of the emptying pipeline is large.
7.The measured values fluctuate
The detector is aging, the internal resistance is large, and the electrode contact is bad.
The sample gas contains high humidity or water droplets, and is gasified in the detector.
8.Measured limit drift, signal overreach
The detector has components damaged, such as zirconium tube rupture, electrode lead open circuit, detector aging, temperature compensation resistance rupture (oxygen content 100%).
9.Causes and symptoms of probe aging
Usually the probe aging is the aging of the zirconia detector, which is mainly manifested in the increase of internal resistance and the increase of background potential.
(1)Increased internal resistance
In practical application, the internal resistance caused by the aging of the probe increases more. The internal resistance is the input resistance between the two ends of the signal line, which is the sum of the lead resistance, the interface resistance between the electrode and zirconia and the volume resistance of zirconia, so the electrode volatilization, the electrode falling off and the reverse stability of zirconia electrolyte (from stable zirconia to unstable zirconia) will cause the internal resistance to rise. The internal resistance of the detector can be measured to determine its aging. According to the experience, when the internal resistance increases close to the limit of its use, there will be a phenomenon of signal beating, some of the response is slow. For these detectors, the background potential is not necessarily large.
(2)Background potential increased

The background potential is the battery additional potential. There are two factors that cause the background potential to increase: One kind belongs to the permanent factor, it parasitic on the battery, such as SO2 and SO3 corrosion, battery asymmetry factor; The other is temporary storage factor, such as the ash of the electrode, air convection and other factors, once the conditions improve, the background potential can be reduced.
The increase of background potential often reflects the aging degree of the detector. When the E0 value exceeds the maximum amount of the analyzer, the detector is damaged.
For example: 
A zirconium oxide, E0 is -5mV at the time of shipment, the allowable range of change is 0-30mV, after half a year of use, it becomes -13mV; After 18 months of use, it becomes -29mV; This indicates that the detector is aged and needs to be replaced.
It is important to note that the aging of some detectors is shown to be on the background potential becomes large, while some detectors are aging but not present, so we need to take this seriously. When the background potential becomes larger because of temporary storage factors, it is possible that the background potential becomes larger first and then smaller with the time of use.
Because of the increase of the background potential, the number of probe aging is less than the number of internal resistance increase, the only background increase, the signal does not jump.
10.Precautions

(1)It is necessary to control the pressure of the sample gas. Usually the pressure of the instrument should not be more than 0.05MPA.

(2)The output pressure of the secondary standard meter shall not be more than 0.30MPA
(3)All the pipelines entering the instrument must be strictly checked for leakage, and this work in the normal work of the instrument must be conducted once every six months.
(4)Before entering the instrument, it must pass through a physical filter of 10u. If the gas resistance phenomenon is found, the filter screen (filter) can be checked first;
(5)Periodically clean the fan filter screen of the analyzer, once every quarter; The environment is bad and needs to be cleaned frequently to prevent the instrument overheating phenomenon caused by poor ventilation;
(6)The installation part of the instrument shall be horizontal and far from the vibration source; The error caused by the uneven convection of the sample caused by the detector is prevented.
(7)The surrounding environment of the analyzer requires good ventilation, avoid closed space, and the measurement error caused by the imbalance of oxygen quantity.
(8)It is very difficult to detect the gas around the analyzer, which will affect the accuracy of the detector
(9)Because the detection is operated at high temperature, if the gas to be detected contains H2, CO and CH4, the matter will react with oxygen, consume part of oxygen, the oxygen concentration is reduced, and the measurement error is caused. Therefore, this factor should be taken into account when the instrument is measuring the gases containing combustible substances to avoid the measurement misalignment.
(10)When measuring corrosive gas, activated carbon is used to filter.