The critical portion of any thermal mass flow meter is the factory calibration whether it may be a capillary-tube type or dispersion type. The flow rate measured by the thermal flow meter is an inferred measurement.
As we already know from its operating principle that the power required for maintaining this temperature differential is directly proportional to the mass flow rate. This relationship between power and mass flow rate is established during the calibration. Each sensor has slightly different heat transfer properties than that of another sensor. Hence, each instrument needs to be individually calibrated.
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