Thermal conductivity gas analyzer
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2020-04-16 15:32:31Source：昶艾电子 Hits：
1.Calibration
①The analyzer must be preheated to thermal stability before calibration (note: The instrument must be preheated with ventilation, otherwise the components will be burned).
②The thermal conductivity of the background gas in the standard gas should be consistent with that of the measured gas, otherwise it should be corrected
③ The standard gas flow rate should be equal to the measured gas flow rate during operation.
④In manual calibration, it should be noted to meet the requirements of instrument switching time, otherwise it may lead to wrong calibration results. For example, when the zero point is calibrated, the zero point gas should be turned on and the zero point should be adjusted by 1min. The zero point calibration is switched to the range calibration, the time interval is about 1min, plus the range calibration also has 1min waiting, so there is about 2min time interval. This time delay takes into account the full displacement and stability of the gas flow in the gas path.
⑤ Some points to be corrected when accurate calibration is needed
2.Common failures and possible causes (see Table 6-3)
3.Method for examining and repairing heat conducting pool
As the hot wire of bridge arm, especially bare wire, it is delicate and fragile and easy to be damaged. Moreover, the installation of hot wire is very careful, its verticality and eccentricity are slightly different, which will bring a direct impact on the measurement accuracy. Therefore, if it is unnecessary, it is better not easy to dismantle. The repair method of the heat conducting pool is as follows.
①Unscrew the anchor screw that leads the measurement arm and reference arm, remove the lead, remove the pressure cap that secures the hot wire, and gently lift the hot wire. Closed reference chamber should never be removable, otherwise it would lead to leakage of the sealed gas in the reference chamber and the instrument would not be usable.
②Clean and dry instrument air is used to sweep the inner hole of the heat conducting pool. If the pollution is serious, the organic solvent and the anhydrous alcohol can be dissolved and cleaned, and then the instrument air is used for drying.
③The resistance value of the hot wire is measured by the digital multimeter. The resistance value of the hot wire at normal temperature should be consistent with the data given by the relevant data, and the resistance value of the four bridge arms should be matched, otherwise the hot wire should be replaced. To replace the hot wire, ensure the symmetry of the four bridge arms.
④The above method can be used to clean the hot wire covered with the glass film, and at the same time, it is necessary to check whether the glass film of the hot wire is cracked and whether the lead wire is abnormal. Replace the aged or scarred bridge arm seal O-ring.
⑤Restore the clean hot-conductive pool installation to ensure that the hot wire is centered and vertical
⑥The installed heat conduction pool should be strictly checked for air tightness. The check method is that the heat conduction pool is sealed with 10kPa pressure, and the 15min pressure drop should not be more than 0.4kPa.
