Method and apparatus for detecting and controlling mass flow

A process mass flow instrument for measuring the mass flow rate of a process fluid comprising:

• a fluid inlet;
• a fluid outlet;
• a flow passage connecting the fluid inlet and the fluid outlet;
• a fluid flow sensor which provides a raw output signal corresponding to an unknown mass flow rate;
• and
• a processor;
• the processor containing a conversion routine for converting the raw output signal to an adjusted signal indicating the mass flow rate of the process fluid, wherein the conversion routine is empirically derived using at least one calibration mass flow instrument which is similar to the process mass flow instrument to correlate the output signals of the calibration mass flow instrument sensing the mass flow of a calibration fluid which is different than the process fluid with the output signals of the calibration mass flow instrument sensing the mass flow of the process fluid.