Laminar Flow Elements (LFE) force gas to flow through a narrow passageway producing a pressure drop in the gas proportional to the flow rate. The pressure drop is measured and from this the the gas flow rate is calculated. The pressure drop across a LFE is governed by the Poiseuille equation and is a function of the laminar flow element geometry and the gas temperature, pressure, and viscosity. Below are the recommended steps to verify a LFE located upstream of a Mass Flow Controller (MFC) using a primary gas flow calibrator.
- Connect the equipment as per the above configuration. Connect the LFE upstream of the MFC and the primary flow calibrator downstream.
- Turn on the primary flow meter and set the measurement type of STD or VOL depending on the calibration mode. Set the primary flow calibrator standardizing temperature to match the LFE standardizing temperature if the measurement type is set to STD.
- Turn on the flow. Using the pressure regulator, adjust the pressure to the LFE until the downstream pressure of the LFE matches to the rated inlet pressure of the MFC.
- Set the flow to the MFC
- Press READ or AUTO in the primary flow calibrator to begin taking readings. Determine the full scale accuracy of the LFE meter using the following Formula:
% Accuracy= (Gas flow calibrator rate-LFE meter flow rate)*100 / LFE meter flow rate %
Do not forget to allow the MFC to warm up before beginning the calibration, wait several minutes when changing the MFC flow rate, and allow the primary flow calibrator to stabilize before beginning a calibration for optimum measurement results.
Mesa Labs is a recognized leader in primary gas flow calibration measurement and offers and ML-800 that can be used in this process. For more information on the gas flow products Mesa offers please visit:
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