Thermal gas mass flowmeters provide far more robust flow data than any displacement or hot-wire based flow transducers due to their greater and intrinsic thermal stability. Volumetric flow as indicated by a rotameter variable area type flowmeter will have far greater errors.
Modest pricing creates a viable alternative to variable area flowmeters and, for the first time, provide their users with flow data at least 5 times more accurate and with an electrical output for control or data logging.