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Possible reasons for inconsistent comparison readings between two Alicat flow meters: When two Alicat flow meters have inconsistent comparison readings, do not directly determine that there is a problem with the flow meter. Here are some possible reasons and inspection methods that may cause inconsistent readings:
1. Selection of reference flow meter. Accuracy issue: Is the accuracy of the reference flow meter the same or higher than that of the tested flow meter? Suggest using higher precision flow meters as reference standards. Calibration status: Has the flow meter been calibrated recently? It is not recommended to use flow meters that have not been calibrated for a long time as reference standards. Range matching: Is the reference flow meter range close to or slightly larger than the tested flow meter? A close range can ensure the accuracy of comparison. Measurement principle: What is the measurement principle based on a flow meter, and is the measurement result a mass flow rate? It is recommended to choose a mass flow meter as the reference flow meter, or a flow meter whose reading can be converted to standard mass flow rate. The volumetric flow rate under operating conditions is not comparable due to system pressure loss and pressure loss of the flow meter itself.
2. Pipeline connection issues: System air leakage: Are the pipelines, connectors, and threaded interfaces leaking?
? System leakage can cause inconsistent readings between two flow meters. Pipeline length: Is the pipeline between the two flow meters too long? The length of the connecting pipeline between the tested flowmeter and the reference flowmeter should be shortened as much as possible to reduce errors.III. Parameter Setting Issues Standard Setting: Are the STP or NTP standard temperature and pressure settings of the two flow meters consistent?
? Both must be set to the same standard temperature and standard pressure. Zeroing operation: Did the flowmeter reset to zero when there was no airflow passing through before testing? If there is no airflow and the flow reading is not zero, it is recommended to use the reset button TARE to reset before conducting a ventilation test.4. Medium gas problem Gas type: Are the gas types selected for the two flow meters consistent?
? Is the gas mode consistent with the actual tested gas? It is necessary to ensure that the gas mode selected by both parties is consistent with the actual tested gas. Temperature and pressure range: Test whether the temperature and pressure of the gas are within the normal operating range of the two flow meters, and whether they are close to the calibration temperature and pressure of the two flow meters? It is generally recommended to use gases at room temperature and atmospheric pressure for testing. Too low or too high temperature, and too high pressure, may cause additional flow errors. Gas purity: Test whether the gas is dry and pure? If the gas contains a large amount of water vapor, particulate matter, oil fume, and impurities, it may cause additional measurement errors.Fifth, other questions. Data recording unit: Is the data recording the quality flow rate of the standard condition?
? Misunderstanding the volumetric flow rate of the operating conditions as the mass flow rate can also lead to reading deviations between the two. The units of mass flow are generally
