USAGE OF A MFC/MFM FOR A DIFFERENT GAS THAN IT IS CALIBRATED FOR

When a Mass Flow Meter is operated with a gas other than the one it was calibrated for, a scale shift will occur in the relationship between the output signal and the mass flow rate, resulting in a difference in heat capacities between the two gases. This scale shift can be calculated by using the ratio of the molar specific heat of the two gases, or the sensor conversion factor. An evaluation of the scale shift may be done by multiplying the output reading by the ratio of the gas factor of the desired gas, and the gas factor of the calibrated gas.

Actual gas flow Rate = Output reading X (factor of the new gas(*) / factor of the calibrated gas(*))

(*) Gas factor are available at the gas data and compatibility section

Warning- To prevent any direct or indirect damage or injury resulting from the use of a MFM with a different gas than the one it is calibrated for, you must certify that all its components are compatible with the new gas before executing any trial.

When a Mass Flow Controller is operated with a gas other than the one it was calibrated for, you should estimate the maximum flow allowed by its valve orifice. Comparing the valve orifice factor can provide an estimation.

Maximum new gas flow rate = Calibrated Maximum flow rate X (Orifice factor of the calibrated gas / Orifice factor of the new gas)