Correct way to measure FID flow rates

[unhpian]

What is the correct way to measure FID flow rates? I have a digital flow meter with a button to change the gas being measured which accounts for difference in density. Our FID calls for a H2 flow rate of 40 mL/min, and air of 450 mL/min, and I have been measuring it using the meter set to the appropriate gas, which presumably gives a "adjusted" flow rate. Is this correct, or should I just use the "air" setting for both, that way the ratio is a true volumetric ratio?

[Consumer Products Guy]

If you really care that much: measure each gas with the flow meter set for that type of gas.

[Peter Apps]

If the flow meter really is calibrated for different gasses it must be correcting for more than just density (thermal conductivity for a start I would think). I'm with CPG; if it has a setting for each gas go ahead and use them.

The only reason that I can think of for correcting for only density is if the readout is in mass per unit time. Which would be strange. What make and model is it ?

Peter